Bio

Academic Appointments


Administrative Appointments


  • Chair, MS senate task force on posdoctoral affairs (2009 - 2012)
  • Member, MS senate steering committee (2008 - 2012)
  • Senator, Medical School senate (2006 - 2012)
  • Member, Stanford Human Subjects Panel (2000 - 2004)
  • Member, Administrative Panel on Biosafety, Stanford University (1995 - 1996)
  • Chair, Department Admissions Committee, Stanford University (1985 - 1988)
  • Chair, Stanford Recombiant DNA Panel, Stanford University (1981 - 1982)
  • Member, Stanford Recombinant DNA Panel, Stanford University (1979 - 1982)
  • Member, Stanford Panel on human subjects, Stanford University (2000 - 2004)

Honors & Awards


  • Editorial Board, Journal of Molecular Imaging & Dynamic (2010-present)
  • Editorial Board, Cancer Management and Research (2008-present)
  • Editor-in-Chief, Open Journal of Applied Sciences (2012)
  • Chartered Member, Drug Discovery & Molecular Pharmacology Study section, NCI (2008-2012)
  • Elected Fellow, American Academy of Microbiology (1994-)
  • Star Award, Environmental Protection Agency (1991,1997)
  • Review Committee Member, Accreditation Board for Engineering and Technology (1992)
  • Foundation for Microbiology Lecturer, American Society for Microbiology (1991-1993)
  • Fulbright Scholar, Fulbright Foundation (1964-1971)
  • Expert consultant and witness, Law Offices of Swidler Berlin Shereff Friedman, LLP. (1999 - 2001)
  • Member, Advisory Board, Chemgen Pharma International (2004-2008)
  • Member, Advisory Board, Chembiotek (2002 - 2004)
  • Board Member, Scientific Advisory Board, Institute of Molecular Medicine, New York, Kolkata (2002-2004)
  • Member Study Section, National Aeronautics and Space Administration (2001, 2004, 2008, 2011)
  • Member Study Section, NIH Environmental Institute (2003)
  • Editorial Board Member: Journal of Bacteriology:, American Society for Microbiology (1987-1993)
  • Member Study Section, Department of Energy (1996, 1997, 2002)
  • Member Study Section, National Institutes of Health (2003)
  • Editorial Board, Annual Review of Microbiology (1980-1983, 2005)

Professional Education


  • Ph. D., University of California, Microbiology (1969)

Community and International Work


  • Bacterial antibiotic resistance in space flight, Stanford University; NASA Ames

    Topic

    Genetic basis of resistance

    Partnering Organization(s)

    NASA

    Location

    Bay Area

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    Yes

  • Nuclear waste remediation

    Topic

    Bioengineering

    Partnering Organization(s)

    Cadarache, France

    Location

    International

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    Yes

  • Lectures

    Ongoing Project

    Yes

    Opportunities for Student Involvement

    No

Research & Scholarship

Current Research and Scholarly Interests


Please follow myResearch/
Lab website link: http://www.stanford.edu/~amatin/MatinLabHomePage/MatinLabHome-Page.htm

Teaching

2013-14 Courses


Postdoctoral Advisees


Publications

Journal Articles


  • Crystal Structure of ChrR-A Quinone Reductase with the Capacity to Reduce Chromate PLOS ONE Eswaramoorthy, S., Poulain, S., Hienerwadel, R., Bremond, N., Sylvester, M. D., Zhang, Y., Berthomieu, C., van der Lelie, D., Matin, A. 2012; 7 (4)

    Abstract

    The Escherichia coli ChrR enzyme is an obligatory two-electron quinone reductase that has many applications, such as in chromate bioremediation. Its crystal structure, solved at 2.2 Å resolution, shows that it belongs to the flavodoxin superfamily in which flavin mononucleotide (FMN) is firmly anchored to the protein. ChrR crystallized as a tetramer, and size exclusion chromatography showed that this is the oligomeric form that catalyzes chromate reduction. Within the tetramer, the dimers interact by a pair of two hydrogen bond networks, each involving Tyr128 and Glu146 of one dimer and Arg125 and Tyr85 of the other; the latter extends to one of the redox FMN cofactors. Changes in each of these amino acids enhanced chromate reductase activity of the enzyme, showing that this network is centrally involved in chromate reduction.

    View details for DOI 10.1371/journal.pone.0036017

    View details for Web of Science ID 000305336000101

    View details for PubMedID 22558308

  • New Device for High-Throughput Viability Screening of Flow Biofilms APPLIED AND ENVIRONMENTAL MICROBIOLOGY Benoit, M. R., Conant, C. G., Ionescu-Zanetti, C., Schwartz, M., Matin, A. 2010; 76 (13): 4136-4142

    Abstract

    Control of biofilms requires rapid methods to identify compounds effective against them and to isolate resistance-compromised mutants for identifying genes involved in enhanced biofilm resistance. While rapid screening methods for microtiter plate well ("static") biofilms are available, there are no methods for such screening of continuous flow biofilms ("flow biofilms"). Since the latter biofilms more closely approximate natural biofilms, development of a high-throughput (HTP) method for screening them is desirable. We describe here a new method using a device comprised of microfluidic channels and a distributed pneumatic pump (BioFlux) that provides fluid flow to 96 individual biofilms. This device allows fine control of continuous or intermittent fluid flow over a broad range of flow rates, and the use of a standard well plate format provides compatibility with plate readers. We show that use of green fluorescent protein (GFP)-expressing bacteria, staining with propidium iodide, and measurement of fluorescence with a plate reader permit rapid and accurate determination of biofilm viability. The biofilm viability measured with the plate reader agreed with that determined using plate counts, as well as with the results of fluorescence microscope image analysis. Using BioFlux and the plate reader, we were able to rapidly screen the effects of several antimicrobials on the viability of Pseudomonas aeruginosa PAO1 flow biofilms.

    View details for DOI 10.1128/AEM.03065-09

    View details for Web of Science ID 000279082800003

    View details for PubMedID 20435763

  • Role of nitric oxide in Salmonella typhimurium-mediated cancer cell killing BMC CANCER Barak, Y., Schreiber, F., Thorne, S. H., Contag, C. H., deBeer, D., Matin, A. 2010; 10

    Abstract

    Bacterial targeting of tumours is an important anti-cancer strategy. We previously showed that strain SL7838 of Salmonella typhimurium targets and kills cancer cells. Whether NO generation by the bacteria has a role in SL7838 lethality to cancer cells is explored. This bacterium has the mechanism for generating NO, but also for decomposing it.Mechanism underlying Salmonella typhimurium tumour therapy was investigated through in vitro and in vivo studies. NO measurements were conducted either by chemical assays (in vitro) or using Biosensors (in vivo). Cancer cells cytotoxic assay were done by using MTS. Bacterial cell survival and tumour burden were determined using molecular imaging techniques.SL7838 generated nitric oxide (NO) in anaerobic cell suspensions, inside infected cancer cells in vitro and in implanted 4T1 tumours in live mice, the last, as measured using microsensors. Thus, under these conditions, the NO generating pathway is more active than the decomposition pathway. The latter was eliminated, in strain SL7842, by the deletion of hmp- and norV genes, making SL7842 more proficient at generating NO than SL7838. SL7842 killed cancer cells more effectively than SL7838 in vitro, and this was dependent on nitrate availability. This strain was also ca. 100% more effective in treating implanted 4T1 mouse tumours than SL7838.NO generation capability is important in the killing of cancer cells by Salmonella strains.

    View details for DOI 10.1186/1471-2407-10-146

    View details for Web of Science ID 000277802300001

    View details for PubMedID 20398414

  • Visualizing Implanted Tumors in Mice with Magnetic Resonance Imaging Using Magnetotactic Bacteria CLINICAL CANCER RESEARCH Benoit, M. R., Mayer, D., Barak, Y., Chen, I. Y., Hu, W., Cheng, Z., Wang, S. X., Spielman, D. M., Gambhir, S. S., Matin, A. 2009; 15 (16): 5170-5177

    Abstract

    To determine if magnetotactic bacteria can target tumors in mice and provide positive contrast for visualization using magnetic resonance imaging.The ability of the magnetotactic bacterium, Magnetospirillum magneticum AMB-1 (referred to from here as AMB-1), to confer positive magnetic resonance imaging contrast was determined in vitro and in vivo. For the latter studies, AMB-1 were injected either i.t. or i.v. Bacterial growth conditions were manipulated to produce small (approximately 25-nm diameter) magnetite particles, which were observed using transmission electron microscopy. Tumor targeting was confirmed using 64Cu-labeled bacteria and positron emission tomography and by determination of viable cell counts recovered from different organs and the tumor.We show that AMB-1 bacteria with small magnetite particles generate T1-weighted positive contrast, enhancing in vivo visualization by magnetic resonance imaging. Following i.v. injection of 64Cu-labeled AMB-1, positron emission tomography imaging revealed increasing colonization of tumors and decreasing infection of organs after 4 hours. Viable cell counts showed that, by day 6, the bacteria had colonized tumors but were cleared completely from other organs. Magnetic resonance imaging showed a 1.22-fold (P = 0.003) increased positive contrast in tumors on day 2 and a 1.39-fold increase (P = 0.0007) on day 6.Magnetotactic bacteria can produce positive magnetic resonance imaging contrast and colonize mouse tumor xenografts, providing a potential tool for improved magnetic resonance imaging visualization in preclinical and translational studies to track cancer.

    View details for DOI 10.1158/1078-0432.CCR-08-3206

    View details for Web of Science ID 000269024900019

    View details for PubMedID 19671860

  • CNOB/ChrR6, a new prodrug enzyme cancer chemotherapy MOLECULAR CANCER THERAPEUTICS Thorne, S. H., Barak, Y., Liang, W., Bachmann, M. H., Rao, J., Contag, C. H., Matin, A. 2009; 8 (2): 333-341

    Abstract

    We report the discovery of a new prodrug, 6-chloro-9-nitro-5-oxo-5H-benzo(a)phenoxazine (CNOB). This prodrug is efficiently activated by ChrR6, the highly active prodrug activating bacterial enzyme we have previously developed. The CNOB/ChrR6 therapy was effective in killing several cancer cell lines in vitro. It also efficiently treated tumors in mice with up to 40% complete remission. 9-Amino-6-chloro-5H-benzo(a)phenoxazine-5-one (MCHB) was the only product of CNOB reduction by ChrR6. MCHB binds DNA; at nonlethal concentration, it causes cell accumulation in the S phase, and at lethal dose, it induces cell surface Annexin V and caspase-3 and caspase-9 activities. Further, MCHB colocalizes with mitochondria and disrupts their electrochemical potential. Thus, killing by CNOB involves MCHB, which likely induces apoptosis through the mitochondrial pathway. An attractive feature of the CNOB/ChrR6 regimen is that its toxic product, MCHB, is fluorescent. This feature proved helpful in in vitro studies because simple fluorescence measurements provided information on the kinetics of CNOB activation within the cells, MCHB killing mechanism, its generally efficient bystander effect in cells and cell spheroids, and its biodistribution. The emission wavelength of MCHB also permitted its visualization in live animals, allowing noninvasive qualitative imaging of MCHB in mice and the tumor microenvironment. This feature may simplify exploration of barriers to the penetration of MCHB in tumors and their amelioration.

    View details for DOI 10.1158/1535-7163.MCT-08-0707

    View details for Web of Science ID 000263397300008

    View details for PubMedID 19190118

  • Enzyme improvement in the absence of structural knowledge: a novel statistical approach ISME JOURNAL Barak, Y., Nov, Y., Ackerley, D. F., Matin, A. 2008; 2 (2): 171-179

    Abstract

    Most existing methods for improving protein activity are laborious and costly, as they either require knowledge of protein structure or involve expression and screening of a vast number of protein mutants. We describe here a successful first application of a novel approach, which requires no structural knowledge and is shown to significantly reduce the number of mutants that need to be screened. In the first phase of this study, around 7000 mutants were screened through standard directed evolution, yielding a 230-fold improvement in activity relative to the wild type. Using sequence analysis and site-directed mutagenesis, an additional single mutant was then produced, with 500-fold improved activity. In the second phase, a novel statistical method for protein improvement was used; building on data from the first phase, only 11 targeted additional mutants were produced through site-directed mutagenesis, and the best among them achieved a >1500-fold improvement in activity over the wild type. Thus, the statistical model underlying the experiment was validated, and its predictions were shown to reduce laboratory labor and resources.

    View details for DOI 10.1038/ismej.2007.100

    View details for Web of Science ID 000253492900005

    View details for PubMedID 18253133

  • Role of the rapA gene in controlling antibiotic resistance of Escherichia coli biofilms ANTIMICROBIAL AGENTS AND CHEMOTHERAPY Lynch, S. V., Dixon, L., Benoit, M. R., Brodie, E. L., Keyhan, M., Hu, P., Ackerley, D. F., Andersen, G. L., Matin, A. 2007; 51 (10): 3650-3658

    Abstract

    By using a high-throughput screening method, a mutant of a uropathogenic Escherichia coli strain affected in the rapA gene was isolated. The mutant formed normal-architecture biofilms but showed decreased penicillin G resistance, although the mutation did not affect planktonic cell resistance. Transcriptome analysis showed that 22 genes were down-regulated in the mutant biofilm. One of these genes was yhcQ, which encodes a putative multidrug resistance pump. Mutants with mutations in this gene also formed biofilms with decreased resistance, although the effect was less pronounced than that of the rapA mutation. Thus, an additional mechanism(s) controlled by a rapA-regulated gene(s) was involved in wild-type biofilm resistance. The search for this mechanism was guided by the fact that another down-regulated gene in rapA biofilms, yeeZ, is suspected to be involved in extra cell wall-related functions. A comparison of the biofilm matrix of the wild-type and rapA strains revealed decreased polysaccharide quantities and coverage in the mutant biofilms. Furthermore, the (fluorescent) functional penicillin G homologue Bocillin FL penetrated the mutant biofilms more readily. The results strongly suggest a dual mechanism for the wild-type biofilm penicillin G resistance, retarded penetration, and effective efflux. The results of studies with an E. coli K-12 strain pointed to the same conclusion. Since efflux and penetration can be general resistance mechanisms, tests were conducted with other antibiotics. The rapA biofilm was also more sensitive to norfloxacin, chloramphenicol, and gentamicin.

    View details for DOI 10.1128/AAC.00601-07

    View details for Web of Science ID 000249794800025

    View details for PubMedID 17664315

  • Escherichia coli biofilms formed under low-shear modeled microgravity in a ground-based system APPLIED AND ENVIRONMENTAL MICROBIOLOGY Lynch, S. V., Mukundakrishnan, K., Benoit, M. R., Ayyaswamy, P. S., Matin, A. 2006; 72 (12): 7701-7710

    Abstract

    Bacterial biofilms cause chronic diseases that are difficult to control. Since biofilm formation in space is well documented and planktonic cells become more resistant and virulent under modeled microgravity, it is important to determine the effect of this gravity condition on biofilms. Inclusion of glass microcarrier beads of appropriate dimensions and density with medium and inoculum, in vessels specially designed to permit ground-based investigations into aspects of low-shear modeled microgravity (LSMMG), facilitated these studies. Mathematical modeling of microcarrier behavior based on experimental conditions demonstrated that they satisfied the criteria for LSMMG conditions. Experimental observations confirmed that the microcarrier trajectory in the LSMMG vessel concurred with the predicted model. At 24 h, the LSMMG Escherichia coli biofilms were thicker than their normal-gravity counterparts and exhibited increased resistance to the general stressors salt and ethanol and to two antibiotics (penicillin and chloramphenicol). Biofilms of a mutant of E. coli, deficient in sigma(s), were impaired in developing LSMMG-conferred resistance to the general stressors but not to the antibiotics, indicating two separate pathways of LSMMG-conferred resistance.

    View details for DOI 10.1128/AEM.01294-06

    View details for Web of Science ID 000242681300035

    View details for PubMedID 17028231

  • Analysis of novel soluble chromate and uranyl reductases and generation of an improved enzyme by directed evolution APPLIED AND ENVIRONMENTAL MICROBIOLOGY Barak, Y., Ackerley, D. F., Dodge, C. J., Banwari, L., Alex, C., Francis, A. J., Matin, A. 2006; 72 (11): 7074-7082

    Abstract

    Most polluted sites contain mixed waste. This is especially true of the U.S. Department of Energy (DOE) waste sites which hold a complex mixture of heavy metals, radionuclides, and organic solvents. In such environments enzymes that can remediate multiple pollutants are advantageous. We report here evolution of an enzyme, ChrR6 (formerly referred to as Y6), which shows a markedly enhanced capacity for remediating two of the most serious and prevalent DOE contaminants, chromate and uranyl. ChrR6 is a soluble enzyme and reduces chromate and uranyl intracellularly. Thus, the reduced product is at least partially sequestered and nucleated, minimizing the chances of reoxidation. Only one amino acid change, (Tyr)128(Asn), was responsible for the observed improvement. We show here that ChrR6 makes Pseudomonas putida and Escherichia coli more efficient agents for bioremediation if the cellular permeability barrier to the metals is decreased.

    View details for DOI 10.1128/AEM.01334-06

    View details for Web of Science ID 000242003800027

    View details for PubMedID 17088379

  • Effect of chromate stress on Escherichia coli K-12 JOURNAL OF BACTERIOLOGY Ackerley, D. F., Barak, Y., Lynch, S. V., Curtin, J., Matin, A. 2006; 188 (9): 3371-3381

    Abstract

    The nature of the stress experienced by Escherichia coli K-12 exposed to chromate, and mechanisms that may enable cells to withstand this stress, were examined. Cells that had been preadapted by overnight growth in the presence of chromate were less stressed than nonadapted controls. Within 3 h of chromate exposure, the latter ceased growth and exhibited extreme filamentous morphology; by 5 h there was partial recovery with restoration of relatively normal cell morphology. In contrast, preadapted cells were less drastically affected in their morphology and growth. Cellular oxidative stress, as monitored by use of an H2O2-responsive fluorescent dye, was most severe in the nonadapted cells at 3 h postinoculation, lower in the partially recovered cells at 5 h postinoculation, and lower still in the preadapted cells. Chromate exposure depleted cellular levels of reduced glutathione and other free thiols to a greater extent in nonadapted than preadapted cells. In both cell types, the SOS response was activated, and levels of proteins such as SodB and CysK, which can counter oxidative stress, were increased. Some mutants missing antioxidant proteins (SodB, CysK, YieF, or KatE) were more sensitive to chromate. Thus, oxidative stress plays a major role in chromate toxicity in vivo, and cellular defense against this toxicity involves activation of antioxidant mechanisms. As bacterial chromate bioremediation is limited by the toxicity of chromate, minimizing oxidative stress during bacterial chromate reduction and bolstering the capacity of these organisms to deal with this stress will improve their effectiveness in chromate bioremediation.

    View details for DOI 10.1128/JB.188.9.3371-3381.2006

    View details for Web of Science ID 000237171200026

    View details for PubMedID 16621832

  • New enzyme for reductive cancer chemotherapy, YieF, and its improvement by directed evolution MOLECULAR CANCER THERAPEUTICS Barak, Y., Thorne, S. H., Ackerley, D. F., Lynch, S. V., Contag, C. H., Matin, A. 2006; 5 (1): 97-103

    Abstract

    Reductive prodrugs, mitomycin C and 5-aziridinyl-2,4-dinitrobenzamide (CB 1954), are nontoxic in their native form but become highly toxic upon reduction. Their effectiveness in cancer chemotherapy can be enhanced by delivering to tumors enzymes with improved prodrug reduction kinetics. We report the discovery of a new prodrug-reducing enzyme, YieF, from Escherichia coli, and the improvement of its kinetics for reducing mitomycin C and CB 1954. A YieF-derived enzyme, Y6, killed HeLa spinner cells with >or=5-fold efficiency than the wild-type enzymes, YieF and NfsA, at a variety of drug and enzyme concentrations and incubation times. With adhered HeLa cells and Salmonella typhimurium SL 7838 bacteria as enzyme delivery vehicle, at least an order of magnitude less of Y6-producing bacteria were required to kill >90% of tumor cells compared with bacteria expressing the wild-type enzymes, which at a comparable level killed < 5% of the cells. Thus, Y6 is a promising enzyme for use in cancer chemotherapy, and Salmonella strain SL 7838, which specifically targets tumors, may be used to deliver the prodrug-activating enzymes to tumors.

    View details for DOI 10.1158/1535-7163.MCT-05-0365

    View details for Web of Science ID 000234772900011

    View details for PubMedID 16432167

  • ChrR, a soluble quinone reductase of Pseudomonas putida that defends against H2O2 JOURNAL OF BIOLOGICAL CHEMISTRY Gonzalez, C. F., Ackerley, D. F., Lynch, S. V., Matin, A. 2005; 280 (24): 22590-22595

    Abstract

    Most bacteria contain soluble quinone-reducing flavoenzymes. However, no biological benefit for this activity has previously been demonstrated. ChrR of Pseudomonas putida is one such enzyme that has also been characterized as a chromate reductase; yet we propose that it is the quinone-reducing activity of ChrR that has the greatest biological significance. ChrR reduces quinones by simultaneous two-electron transfer, avoiding formation of highly reactive semiquinone intermediates and producing quinols that promote tolerance of H(2)O(2). Expression of chrR was induced by H(2)O(2), and levels of chrR expression in overexpressing, wild type, and knock-out mutant strains correlated with the H(2)O(2) tolerance and scavenging ability of each strain. The chrR expression level also correlated with intracellular H(2)O(2) levels as measured by protein carbonylation assays and fluorescence-activated cell scanning analysis with the H(2)O(2)-responsive dye H(2)DCFDA. Thus, enhancing the activity of ChrR in a chromate-remediating bacterial strain may not only increase the rate of chromate transformation, it may also augment the capacity of these cells to withstand the unavoidable production of H(2)O(2) that accompanies chromate reduction.

    View details for DOI 10.1074/jbc.M501654200

    View details for Web of Science ID 000229741800007

    View details for PubMedID 15840577

  • Investigating the threat of bacteria grown in space ASM NEWS Matin, A., Lynch, S. V. 2005; 71 (5): 235-240
  • Biomolecular strategy to decrease chromate toxicity to remediating bacteria WATER RESOURCES MANAGEMENT III Ackerley, D. F., Gonzalez, C. F., Keyhan, M., Blake, R., Matin, A. 2005; 80: 259-267
  • Engineering Pseudomonas putida to minimize clogging during biostimulation ENVIRONMENTAL HEALTH RISK III Matin, A., Hahm, D., Ackerley, D. F. 2005; 9: 447-457
  • Role and regulation of sigma(s) in general resistance conferred by low-shear simulated microgravity in Escherichia coli JOURNAL OF BACTERIOLOGY Lynch, S. V., Brodie, E. L., Matin, A. 2004; 186 (24): 8207-8212

    Abstract

    Life on Earth evolved in the presence of gravity, and thus it is of interest from the perspective of space exploration to determine if diminished gravity affects biological processes. Cultivation of Escherichia coli under low-shear simulated microgravity (SMG) conditions resulted in enhanced stress resistance in both exponential- and stationary-phase cells, making the latter superresistant. Given that microgravity of space and SMG also compromise human immune response, this phenomenon constitutes a potential threat to astronauts. As low-shear environments are encountered by pathogens on Earth as well, SMG-conferred resistance is also relevant to controlling infectious disease on this planet. The SMG effect resembles the general stress response on Earth, which makes bacteria resistant to multiple stresses; this response is sigma s dependent, irrespective of the growth phase. However, SMG-induced increased resistance was dependent on sigma s only in stationary phase, being independent of this sigma factor in exponential phase. sigma s concentration was some 30% lower in exponential-phase SMG cells than in normal gravity cells but was twofold higher in stationary-phase SMG cells. While SMG affected sigma s synthesis at all levels of control, the main reasons for the differential effect of this gravity condition on sigma s levels were that it rendered the sigma protein less stable in exponential phase and increased rpoS mRNA translational efficiency. Since sigma s regulatory processes are influenced by mRNA and protein-folding patterns, the data suggest that SMG may affect these configurations.

    View details for DOI 10.1128/JB.186.24.8207-8212.2004

    View details for Web of Science ID 000225670300006

    View details for PubMedID 15576768

  • Mechanism of chromate reduction by the Escherichia coli protein, NfsA, and the role of different chromate reductases in minimizing oxidative stress during chromate reduction ENVIRONMENTAL MICROBIOLOGY Ackerley, D. F., Gonzalez, C. F., Keyhan, M., Blake, R., Matin, A. 2004; 6 (8): 851-860

    Abstract

    Chromate [Cr(VI)] is a serious environmental pollutant, which is amenable to bacterial bioremediation. NfsA, the major oxygen-insensitive nitroreductase of Escherichia coli, is a flavoprotein that is able to reduce chromate to less soluble and less toxic Cr(III). We show that this process involves single-electron transfer, giving rise to a flavin semiquinone form of NfsA and Cr(V) as intermediates, which redox cycle, generating more reactive oxygen species (ROS) than a divalent chromate reducer, YieF. However, NfsA generates less ROS than a known one-electron chromate reducer, lipoyl dehydrogenase (LpDH), suggesting that NfsA employs a mixture of uni- and di-valent electron transfer steps. The presence of YieF, ChrR (another chromate reductase we previously characterized), or NfsA in an LpDH-catalysed chromate reduction reaction decreased ROS generation by c. 65, 40, or 20%, respectively, suggesting that these enzymes can pre-empt ROS generation by LpDH. We previously showed that ChrR protects Pseudomonas putida against chromate toxicity; here we show that NfsA or YieF overproduction can also increase the tolerance of E. coli to this compound.

    View details for DOI 10.1111/j.1462-2920.2004.00639.x

    View details for Web of Science ID 000222578600010

    View details for PubMedID 15250887

  • Chromate-reducing properties of soluble Flavoproteins from Pseudomonas putida and Escherichia coli APPLIED AND ENVIRONMENTAL MICROBIOLOGY Ackerley, D. F., Gonzalez, C. F., Park, C. H., Blake, R., Keyhan, A., Matin, A. 2004; 70 (2): 873-882

    Abstract

    Cr(VI) (chromate) is a toxic, soluble environmental contaminant. Bacteria can reduce chromate to the insoluble and less toxic Cr(III), and thus chromate bioremediation is of interest. Genetic and protein engineering of suitable enzymes can improve bacterial bioremediation. Many bacterial enzymes catalyze one-electron reduction of chromate, generating Cr(V), which redox cycles, generating excessive reactive oxygen species (ROS). Such enzymes are not appropriate for bioremediation, as they harm the bacteria and their primary end product is not Cr(III). In this work, the chromate reductase activities of two electrophoretically pure soluble bacterial flavoproteins--ChrR (from Pseudomonas putida) and YieF (from Escherichia coli)-were examined. Both are dimers and reduce chromate efficiently to Cr(III) (kcat/Km = approximately 2 x 10(4) M(-1) x s(-1)). The ChrR dimer generated a flavin semiquinone during chromate reduction and transferred >25% of the NADH electrons to ROS. However, the semiquinone was formed transiently and ROS diminished with time. Thus, ChrR probably generates Cr(V), but only transiently. Studies with mutants showed that ChrR protects against chromate toxicity; this is possibly because it preempts chromate reduction by the cellular one-electron reducers, thereby minimizing ROS generation. ChrR is thus a suitable enzyme for further studies. During chromate reduction by YieF, no flavin semiquinone was generated and only 25% of the NADH electrons were transferred to ROS. The YieF dimer may therefore be an obligatory four-electron chromate reducer which in one step transfers three electrons to chromate and one to molecular oxygen. As a mutant lacking this enzyme could not be obtained, the role of YieF in chromate protection could not be directly explored. The results nevertheless suggest that YieF may be an even more suitable candidate for further studies than ChrR.

    View details for DOI 10.1128/AEM.70.2.873-882.2004

    View details for Web of Science ID 000188854900031

    View details for PubMedID 14766567

  • A soluble flavoprotein contributes to chromate reduction and tolerance by Pseudomonas putida ACTA BIOTECHNOLOGICA Gonzalez, C. F., Ackerley, D. F., Park, C. H., Matin, A. 2003; 23 (2-3): 233-239
  • The stress response of Escherichia coli to conditions of simulated microgravity Abstracts of the 102nd General meeting of the American Society for Microbiology, Washington D.C., A. Matin., Lynch, S. V. 2003
  • Tetracycline rapidly reaches all the constituent cells of uropathogenic Escherichia coli biofilms ANTIMICROBIAL AGENTS AND CHEMOTHERAPY Stone, G., Wood, P., Dixon, L., Keyhan, M., Matin, A. 2002; 46 (8): 2458-2461

    Abstract

    We have developed a method for visualizing Escherichia coli cells that are exposed to tetracycline in a biofilm, based on a previous report that liposomes containing the E. coli TetR(B) protein fluoresce when exposed to this antibiotic. By our method, cells devoid of TetR(B) also exhibited tetracycline-dependent fluorescence. At 50 microg of tetracycline ml(-1), planktonic cells of a uropathogenic E. coli (UPEC) strain developed maximal fluorescence after 7.5 to 10 min of exposure. A similar behavior was exhibited by cells in a 24- or 48-h UPEC biofilm, as examined by confocal laser microscopy, regardless of whether they lined empty spaces or occupied densely packed regions. Further, a comparison of phase-contrast and fluorescent images of corresponding biofilm zones showed that all the cells fluoresced. Thus, all the biofilm cells were exposed to tetracycline and there were no pockets within the biofilm where the antibiotic failed to reach. It also appeared unlikely that niches of reduced exposure to the antibiotic existed within the biofilms.

    View details for DOI 10.1128/AAC.46.8.2458.2461.2002

    View details for Web of Science ID 000176968700021

    View details for PubMedID 12121918

  • Molecular engineering of soluble bacterial proteins with chromate reductase activity REMEDIATION AND BENEFICIAL REUSE OF CONTAMINATED SEDIMENTS Park, C. H., Gonzalez, C., Ackerley, D., Keyhan, M., Matin, A. 2002: 103-111
  • A soluble flavoprotein contributes to chromate reduction and tolerance by Pseudomonas putida. Acta Biotechnology Ackerley DF, Park CH, Gonzalez CF, Keyhan M, Matin A 2002; 23: 233
  • The EmrR protein represses the Escherichia coli emrRAB multidrug resistance operon by directly binding to its promoter region ANTIMICROBIAL AGENTS AND CHEMOTHERAPY Xiong, A., Gottman, A., PARK, C., Baetens, M., Pandza, S., Matin, A. 2000; 44 (10): 2905-2907

    Abstract

    EmrR negatively regulates the transcription of the multidrug resistance pump-encoding operon, emrRAB, by binding to its regulatory region. The binding site spans the promoter and the downstream sequence up to the transcriptional start site of the operon. Structurally unrelated drugs that induce the pump interfere with this binding.

    View details for Web of Science ID 000089402300059

    View details for PubMedID 10991887

  • Purification to homogeneity and characterization of a novel Pseudomonas putida chromate reductase APPLIED AND ENVIRONMENTAL MICROBIOLOGY Park, C. H., Keyhan, M., Wielinga, B., Fendorf, S., Matin, A. 2000; 66 (5): 1788-1795

    Abstract

    Cr(VI) (chromate) is a widespread environmental contaminant. Bacterial chromate reductases can convert soluble and toxic chromate to the insoluble and less toxic Cr(III). Bioremediation can therefore be effective in removing chromate from the environment, especially if the bacterial propensity for such removal is enhanced by genetic and biochemical engineering. To clone the chromate reductase-encoding gene, we purified to homogeneity (>600-fold purification) and characterized a novel soluble chromate reductase from Pseudomonas putida, using ammonium sulfate precipitation (55 to 70%), anion-exchange chromatography (DEAE Sepharose CL-6B), chromatofocusing (Polybuffer exchanger 94), and gel filtration (Superose 12 HR 10/30). The enzyme activity was dependent on NADH or NADPH; the temperature and pH optima for chromate reduction were 80 degrees C and 5, respectively; and the K(m) was 374 microM, with a V(max) of 1.72 micromol/min/mg of protein. Sulfate inhibited the enzyme activity noncompetitively. The reductase activity remained virtually unaltered after 30 min of exposure to 50 degrees C; even exposure to higher temperatures did not immediately inactivate the enzyme. X-ray absorption near-edge-structure spectra showed quantitative conversion of chromate to Cr(III) during the enzyme reaction.

    View details for Web of Science ID 000086805500003

    View details for PubMedID 10788340

  • The G-protein FlhF has a role in polar flagellar placement and general stress response induction in Pseudomonas putida MOLECULAR MICROBIOLOGY Pandza, S., Baetens, M., Park, C. H., Au, T., Keyhan, M., Matin, A. 2000; 36 (2): 414-423

    Abstract

    The flhF gene of Pseudomonas putida, which encodes a GTP-binding protein, is part of the flagellar-motility-chemotaxis operon. Its disruption leads to a random flagellar arrangement in the mutant (MK107) and loss of directional motility in contrast to the wild type, which has polar flagella. The return of a normal flhF allele restores polar flagella and normal motility to MK107; its overexpression triples the flagellar number but does not restore directional motility. As FlhF is homologous to the receptor protein of the signal recognition particle (SRP) pathway of membrane protein translocation, this pathway may have a role in polar flagellar placement in P. putida. MK107 is also compromised in the development of the starvation-induced general stress resistance (SGSR) and effective synthesis of several starvation and exponential phase proteins. While somewhat increased protein secretion in MK107 may contribute to its SGSR impairment, the altered protein synthesis pattern also appears to have a role.

    View details for Web of Science ID 000086980800014

    View details for PubMedID 10792727

  • Survival strategies in the stationary phase MICROBIAL ECOLOGY AND INFECTIOUS DISEASE Matin, A., Baetens, M., Pandza, S., Park, C. H., Waggoner, S. 1999: 30-48
  • The Escherichia coli starvation gene cstC is involved in amino acid catabolism JOURNAL OF BACTERIOLOGY Fraley, C. D., Kim, J. H., McCann, M. P., Matin, A. 1998; 180 (16): 4287-4290

    Abstract

    Escherichia coli strains mutant in the starvation gene cstC grow normally in a mineral salts medium but are impaired in utilizing amino acids as nitrogen sources. They are also compromised in starvation survival, where amino acid catabolism is important. The cstC gene encodes a 406-amino-acid protein that closely resembles the E. coli ArgD protein, which is involved in arginine biosynthesis. We postulate that CstC is a counterpart of ArgD in an amino acid catabolic pathway. The cstC upstream region contains several regulatory consensus sequences. Both sigmaS and sigma54 promoters are probably involved in cstC transcription and appear to compete with each other, presumably to match cstC expression to the cellular amino acid catabolic needs.

    View details for Web of Science ID 000075328400036

    View details for PubMedID 9696780

  • H-NS protein represses transcription of the lux systems of Vibrio fischeri and other luminous bacteria cloned into Escherichia coli CURRENT MICROBIOLOGY Ulitzur, S., Matin, A., Fraley, C., Meighen, E. 1997; 35 (6): 336-342

    Abstract

    High expression in Escherichia coli of the lux system cistron of a luminous bacteria under its own control has been accomplished only for the Vibrio fischeri lux system at high cell density. Mutation of the hns gene in E. coli has resulted in strong expression of the V. fischeri lux system at low cell density even in an rpoS-deleted strain of E. coli that emits very low levels of luminescence. The E. coli double mutant, MC4110 hns::kan rpoS::tet carrying the lux system of V. fischeri, developed high luminescence from the very early stages of cellular growth, regardless of the presence of deletion mutations in the luxI or luxR genes. Moreover, autoinducer synthesis was restored in the double mutant with the luxR-deleted system. plac-controlled V. fischeri luxCDABE genes missing luxI and luxR were dim in E. coli rpoS mutant cells, but had wild-type levels of light in the hns-deleted strain [MC4110 hns rpoS], showing that expression was independent of lux regulators in the absence of H-NS. DNA gyrase inhibitors and DNA intercalating agents also brought about the restoration of luminescence in the rpoS-deficient strain. High expression of the lux systems of Vibrio harveyi, Photobacterium leiognathi, and Xenorhabdus luminescens in E. coli MC4110 hns rpoS cells compared with that in wild-type or rpoS mutants was also accomplished. Taken together, these data suggest that the H-NS protein inhibits transcription in E. coli of the lux systems of all or most luminous bacteria at the luxC gene as well as in the luxRI region of the V. fischeri lux operon. These DNA regions are highly enriched with homopolymeric stretches of poly d(A) and poly d(T) characterizing curved DNA, a preferable site of H-NS binding. The significance of the new findings in understanding the regulatory control of the bacterial lux system is discussed.

    View details for Web of Science ID A1997YG68200004

    View details for PubMedID 9353217

  • The sigma(s) level in starving Escherichia coli cells increases solely as a result of its increased stability, despite decreased synthesis MOLECULAR MICROBIOLOGY Zgurskaya, H. I., Keyhan, M., Matin, A. 1997; 24 (3): 643-651

    Abstract

    The sigma S level in starving (stationary phase) Escherichia coli cells increases four-to sixfold following growth in a defined or a complex medium. Chemostat-grown cells, subjected to increasing carbon starvation, also become progressively richer in sigma S content. These increases occur despite reduced transcription of the sigma S-encoding gene, rpoS, and translation of rpoS mRNA, and result solely from a large increase in the stability of the sigma protein. Previous results, based on rpoS::lacZ transcriptional and translational fusions, and on methionine incorporation in sigma S, had suggested increased synthesis of sigma S in starving cells. Alternative explanations for these results consistent with the conclusions of this paper are discussed.

    View details for Web of Science ID A1997XA65100018

    View details for PubMedID 9179856

  • A bacterial model system for understanding multi-drug resistance MICROBIAL DRUG RESISTANCE Saier, M. H., Paulsen, I. T., Matin, A. 1997; 3 (4): 289-295

    Abstract

    Mankind stands at the crossroads, recognizing the need for a radical change in bacterial disease management. The development of several antimicrobial agents in the 1940s and 1950s allowed man to gain the upper hand in controlling these diseases. However, the horizon is now clouded by the activation in bacteria of cryptic multi-drug resistance (MDR) genes and the spread of plasmid- and integron-born MDR genes through bacterial populations. Unless remedial measures are taken, nearly all currently available antimicrobial agents are likely to soon lose their efficacies. We briefly review the bacterial MDR phenomenon and focus on a recently emerging family of small multi-drug resistance (SMR) pumps which may provide an ideal model system for understanding the MDR phenomenon in general.

    View details for Web of Science ID 000071196200001

    View details for PubMedID 9442481

  • Role of alternate sigma factors in starvation protein synthesis - Novel mechanisms of catabolite repression RESEARCH IN MICROBIOLOGY Matin, A. 1996; 147 (6-7): 494-505

    View details for Web of Science ID A1996VN56100009

    View details for PubMedID 9084761

  • Differential regulation of the mcb and emr operons of Escherichia coli: Role of mcb in multidrug resistance ANTIMICROBIAL AGENTS AND CHEMOTHERAPY Lomovskaya, O., Kawai, F., Matin, A. 1996; 40 (4): 1050-1052

    Abstract

    The mcb operon (which is responsible for microcin B17 production) and the emr operon (which encodes a multidrug resistance pump) share a common negative regulator, EmrR. Nevertheless, compounds that induce the emr operon repress the mcb operon. The pump dedicated to microcin B17 extrusion can also protect the calls against sparfloxacin and other toxic compounds.

    View details for Web of Science ID A1996UD24800048

    View details for PubMedID 8849229

  • Capacity of Helicobacter pylori to generate ionic gradients at low pH is similar to that of bacteria which grow under strongly acidic conditions INFECTION AND IMMUNITY Matin, A., Zychlinsky, E., Keyhan, M., Sachs, G. 1996; 64 (4): 1434-1436

    Abstract

    Helicobacter pylori colonized the highly acidic human gastric mucosa. At pH 3.0 to 7.0, this bacterium maintained a nearly neutral internal pH. Its membrane potential changed reciprocally with the pH gradient so that a relatively constant proton motive force was maintained. Possible, the capacity to maintain an appropriate transmembrane ionic gradient at a low pH contributes to the pathogenic propensities of this bacterium.

    View details for Web of Science ID A1996UC31400051

    View details for PubMedID 8606113

  • Regulation of Escherichia coli starvation sigma factor (sigma(s)) by ClpXP protease JOURNAL OF BACTERIOLOGY Schweder, T., Lee, K. H., Lomovskaya, O., Matin, A. 1996; 178 (2): 470-476

    Abstract

    In Escherichia coli, starvation (stationary-phase)-mediated differentiation involves 50 or more genes and is triggered by an increase in cellular sigma s levels. Western immunoblot analysis showed that in mutants lacking the protease ClpP or its cognate ATPase-containing subunit ClpX, sigma s levels of exponential-phase cells increased to those of stationary-phase wild-type cells. Lack of other potential partners of ClpP, i.e., ClpA or ClpB, or of Lon protease had no effect. In ClpXP-proficient cells, the stability of sigma s increased markedly in stationary-phase compared with exponential-phase cells, but in ClpP-deficient cells, sigma s became virtually completely stable in both phases. There was no decrease in ClpXP levels in stationary-phase wild-type cells. Thus, sigma s probably becomes more resistant to this protease in stationary phase. The reported sigma s-stabilizing effect of the hns mutation also was not due to decreased protease levels. Studies with translational fusions containing different lengths of sigma s coding region suggest that amino acid residues 173 to 188 of this sigma factor may directly or indirectly serve as at least part of the target for ClpXP protease.

    View details for Web of Science ID A1996TP52200020

    View details for PubMedID 8550468

  • USE OF STARVATION PROMOTERS TO LIMIT GROWTH AND SELECTIVELY ENRICH EXPRESSION OF TRICHLOROETHYLENE-TRANSFORMING AND PHENOL-TRANSFORMING ACTIVITY IN RECOMBINANT ESCHERICHIA-COLI (VOL 61, PG 3323, 1995) APPLIED AND ENVIRONMENTAL MICROBIOLOGY Matin, A., Little, C. D., Fraley, C. D., Keyhan, M. 1995; 61 (11): 4140-4140

    Abstract

    Volume 61, no. 9, p. 3323: the title of the article should read as shown above. [This corrects the article on p. 3323 in vol. 61.].

    View details for Web of Science ID A1995TC81100065

    View details for PubMedID 16535172

  • USE OF STARVATION PROMOTERS TO LIMIT GROWTH AND SELECT FOR TRICHLOROETHYLENE AND PHENOL TRANSFORMATION ACTIVITY IN RECOMBINANT ESCHERICHIA-COLI APPLIED AND ENVIRONMENTAL MICROBIOLOGY Matin, A., Little, C. D., Fraley, C. D., Keyhan, M. 1995; 61 (9): 3323-3328

    Abstract

    The expression of much useful bacterial activity is facilitated by rapid growth. This coupling can create problems in bacterial fermentations and in situ bioremediation. In the latter process, for example, it necessitates addition of large amounts of nutrients to contaminated environments, such as aquifers. This approach, termed biostimulation, can be technically difficult. Moreover, the resulting in situ bacterial biomass production can have undesirable consequences. In an attempt to minimize coupling between expression of biodegradative activity and growth, we used Escherichia coli starvation promoters to control toluene monooxygenase synthesis. This enzyme complex can degrade the environmental contaminants trichloroethylene (TCE) and phenol. Totally starving cell suspensions of such strains degraded phenol and TCE. Furthermore, rapid conversions occurred in the postexponential batch or very slow growth (dilution) rate chemostat cultures, and the nutrient demand and biomass formation for transforming a given amount of TCE or phenol were reduced by 60 to 90%. Strong starvation promoters have recently been clones and characterized in environmentally relevant bacteria like Pseudomonas species; thus, starvation promoter-driven degradative systems can now be constructed in such bacteria and tested for in situ efficacy.

    View details for Web of Science ID A1995RT79800022

    View details for PubMedID 7574643

  • EMRR IS A NEGATIVE REGULATOR OF THE ESCHERICHIA-COLI MULTIDRUG-RESISTANCE PUMP EMRAB JOURNAL OF BACTERIOLOGY Lomovskaya, O., Lewis, K., Matin, A. 1995; 177 (9): 2328-2334

    Abstract

    The emrAB locus of Escherichia coli encodes a multidrug resistance pump that protects the cell from several chemically unrelated antimicrobial agents, e.g., the protonophores carbonyl cyanide m-chlorophenylhydrazone (CCCP) and tetrachlorosalicyl anilide and the antibiotics nalidixic acid and thiolactomycin. The mprA gene is located immediately upstream of this locus and was shown to be a repressor of microcin biosynthesis (I. del Castillo, J. M. Gomez, and F. Moreno, J. Bacteriol. 173:3924-3929, 1991). There is a putative transcriptional terminator sequence between the mprA and emrA genes. To locate the emr promoter, single-copy lacZ operon fusions containing different regions of the emr locus were made. Only fusions containing the mprA promoter region were expressed. mprA is thus the first gene of the operon, and we propose that it be renamed emrR. Overproduction of the EmrR protein (with a multicopy vector containing the cloned emrR gene) suppressed transcription of the emr locus. A mutation in the emrR gene led to overexpression of the EmrAB pump and increased resistance to antimicrobial agents. CCCP, nalidixic acid, and a number of other structurally unrelated chemicals induced expression of the emr genes, and the induction required EmrR. We conclude that emrRAB genes constitute an operon and that EmrR serves as a negative regulator of this operon. Some of the chemicals that induce the pump serve as its substrates, suggesting that their extrusion is the natural function of the pump.

    View details for Web of Science ID A1995QW52900013

    View details for PubMedID 7730261

  • A CARBON STARVATION SURVIVAL GENE OF PSEUDOMONAS-PUTIDA IS REGULATED BY SIGMA(54) JOURNAL OF BACTERIOLOGY Kim, Y. J., Watrud, L. S., Matin, A. 1995; 177 (7): 1850-1859

    Abstract

    By using mini-Tn5 transposon mutagenesis, two mutants of Pseudomonas putida ATCC 12633 were isolated which showed a marked increase in their sensitivity to carbon starvation; these mutants are presumably affected in the Pex type of proteins that P. putida induces upon carbon starvation (M. Givskov, L. Eberl, and S. Molin, J. Bacteriol. 176:4816-4824, 1994). The affected genes in our mutants were induced about threefold upon carbon starvation. The promoter region of the starvation gene in the mutant MK107 possessed a strong sigma 54-type-promoter sequence, and deletion analysis suggested that this was the major promoter regulating expression; this was confirmed by transcript mapping in rpoN+ and rpoN mutant backgrounds. The deletion analysis implicated a sequence upstream of the sigma 54 promoter, as well as a region downstream of the transcription start site, in the functioning of the promoter. Two sigma 70-type Pribnow boxes were also detected in the promoter region, but their transcriptional activity in the wild type was very weak. However, in a sigma 54-deficient background, these promoters became stronger. The mechanism and possible physiological role of this phenomenon and the possibility that the sequence upstream of the sigma 54 promoter may have a role in carbon sensing are discussed.

    View details for Web of Science ID A1995QP81000028

    View details for PubMedID 7896711

  • CHARACTERIZATION OF THE SIGMA(38)-DEPENDENT EXPRESSION OF A CORE ESCHERICHIA-COLI STARVATION GENE, PEXB JOURNAL OF BACTERIOLOGY Lomovskaya, O. L., KIDWELL, J. P., Matin, A. 1994; 176 (13): 3928-3935

    Abstract

    A reverse genetics approach was used to clone a pex starvation gene that codes for an 18-kDa polypeptide, designated PexB. Single-copy pexB-lacZ operon fusions were constructed to study transcriptional regulation and the promoter region of this gene. The induction by carbon starvation or osmotic stress was transcriptional and controlled by sigma 38 but was independent of this sigma factor by the oxidative stress; presumably, it was sigma 70 mediated under the latter stress. During nitrogen starvation, the induction was controlled at the posttranscriptional level. The pexB upstream region contained 245 nucleotides within which sequences approximating the consensus for cyclic AMP receptor protein and integration host factor binding sites were discernible. Deletion of 164 bp of the upstream region, which included these consensus sequences, did not affect starvation-or osmotic stress-mediated induction of pexB but abolished its induction by oxidative stress. The same start site was used in transcription during carbon starvation, osmotic stress, or oxidative stress, suggesting that the pexB promoter can be recognized in vivo by both sigma 38 and sigma 70, depending, presumably, on the presence of appropriate transcriptional factors. The -10 and -35 regions of pexB resembled those of some but not all genes known to be controlled by sigma 38.

    View details for Web of Science ID A1994NU75800013

    View details for PubMedID 8021175

  • PHYSIOLOGICAL-RESPONSES OF LACTOCOCCUS-LACTIS ML3 TO ALTERNATING CONDITIONS OF GROWTH AND STARVATION ARCHIVES OF MICROBIOLOGY Kunji, E. R., UBBINK, T., Matin, A., Poolman, B., Konings, W. N. 1993; 159 (4): 372-379
  • THE PUTATIVE SIGMA-FACTOR KATF IS REGULATED POSTTRANSCRIPTIONALLY DURING CARBON STARVATION JOURNAL OF BACTERIOLOGY McCann, M. P., Fraley, C. D., Matin, A. 1993; 175 (7): 2143-2149

    Abstract

    Transcriptional and translational 'lacZ reporter fusions were constructed to the katF gene, which encodes a putative sigma factor centrally involved in starvation-mediated general resistance in Escherichia coli. Transcription of katF was found to increase ca. twofold after carbon starvation in minimal medium. The protein fusion containing the longest fragment of katF induced ca. eightfold under the same conditions, whereas fusions to shorter segments showed only a twofold increase in expression. The protein fusion was expressed at higher levels in a strain containing a katF::Tn10 mutation, indicating katF autoregulation. The posttranscriptional regulation of katF by starvation did not require a component of the spent minimal medium. katF was also posttranscriptionally regulated during entry into late log phase in complex medium. This induction was coincident with an increase in katE transcription, suggesting that the cellular concentration of KatF directly followed the induction of the katF protein fusion.

    View details for Web of Science ID A1993KU49000036

    View details for PubMedID 8458856

  • SIGNIFICANT DISPERSED RECURRENT DNA-SEQUENCES IN THE ESCHERICHIA-COLI GENOME - SEVERAL NEW GROUPS JOURNAL OF MOLECULAR BIOLOGY Blaisdell, B. E., Rudd, K. E., Matin, A., Karlin, S. 1993; 229 (4): 833-848

    Abstract

    New computer and statistical methods were used to determine significant direct and inverted repeats in the Escherichia coli contig sequence collection of aggregate 1.6 x 10(6) base-pairs. Eight groups of mostly new structural repeat identities were uncovered. Apart from the high statistical significance of these repeat sequences, there are suggestive relationships of the group matches in terms of neighboring genes, of genomic distributions, of their texts, and of their potentials for secondary structure. Four of these groups are relatively numerous, 11 to 26 members, one is in coding sequences and three are in non-coding. The coding group consists of the ATP-activated transmembrane component of a typical high-affinity protein-binding transport system. One of the non-coding groups consists of a special rho-independent transcription termination signal closely following an operon. The gene neighbors of this group often appear to be involved in some way in processing RNA or DNA. A second non-coding group has, for one or both neighboring genes, a component of a system responding to stress or starvation for some nutrient.

    View details for Web of Science ID A1993KP93900005

    View details for PubMedID 8445651

  • Physiological responses of Lactococcus lactis ML3 to alternating conditions of growth and starvation. Archives of Microbiology Kunji ERS, Ubbink T, Matin A, Poolman B, Konings WN 1993; 159: 372
  • USE OF GLUCOSE STARVATION TO LIMIT GROWTH AND INDUCE PROTEIN-PRODUCTION IN ESCHERICHIA-COLI BIOTECHNOLOGY AND BIOENGINEERING TUNNER, J. R., Robertson, C. R., Schippa, S., Matin, A. 1992; 40 (2): 271-279

    Abstract

    The use of glucose starvation to uncouple the production of recombinant beta-galactosidase from cell growth in Escherichia coli was investigated. A lacZ operon fusion to the carbon starvation-inducible cst-1 locus was used to control beta-galactosidase synthesis. beta-Galactosidase induction was observed only under aerobic starvation conditions, and its expression continued for 6 h following the onset of glucose starvation. The cessation of beta-galactosidase expression closely correlated with the exhaustion of acetate, an overflow metabolite of glucose, from the culture medium. Our results suggest the primary role of acetate in cst-1-controlled protein expression is that of an energy source. Using this information, we metered acetate to a glucose-starved culture and produced a metabolically sluggish state, where growth was limited to a low linear rate and production of recombinant beta-galactosidase occurred continuously throughout the experiment. The cst-1 controlled beta-galactosidase synthesis was also induced at low dilution rates in a glucose-limited chemostat, suggesting possible applications to high-density cell systems such as glucose-limited recycle reactors. This work demonstrates that by using an appropriate promoter system and nutrient limitation, growth can be restrained while recombinant protein production is induced and maintained.

    View details for Web of Science ID A1992HX27500010

    View details for PubMedID 18601113

  • PHYSIOLOGY, MOLECULAR-BIOLOGY AND APPLICATIONS OF THE BACTERIAL STARVATION RESPONSE JOURNAL OF APPLIED BACTERIOLOGY Matin, A. 1992; 73: S49-S57
  • MOLECULAR ANALYSIS OF THE STARVATION STRESS IN ESCHERICHIA-COLI FEMS MICROBIOLOGY ECOLOGY Matin, A. 1990; 74 (2-3): 185-195
  • BIOENERGETICS PARAMETERS AND TRANSPORT IN OBLIGATE ACIDOPHILES BIOCHIMICA ET BIOPHYSICA ACTA Matin, A. 1990; 1018 (2-3): 267-270
  • KEEPING A NEUTRAL CYTOPLASM - THE BIOENERGETICS OF OBLIGATE ACIDOPHILES FEMS MICROBIOLOGY REVIEWS Matin, A. 1990; 75 (2-3): 307-318
  • RESISTANCE OF BACTERIAL SUBPOPULATIONS TO DISINFECTION BY CHLORINE DIOXIDE JOURNAL AMERICAN WATER WORKS ASSOCIATION Berg, J. D., HOFF, J. C., Roberts, P. V., Matin, A. 1988; 80 (9): 115-119
  • TWO-DIMENSIONAL GEL RESOLUTION OF POLYPEPTIDES SPECIFIC FOR AUTOTROPHIC GROWTH IN THIOBACILLUS-VERSUTUS JOURNAL OF APPLIED BACTERIOLOGY Read, D. L., Matin, A. 1987; 63 (5): 469-472
  • SYNTHESIS OF UNIQUE PROTEINS AT THE ONSET OF CARBON STARVATION IN ESCHERICHIA-COLI JOURNAL OF INDUSTRIAL MICROBIOLOGY Groat, R. G., Matin, A. 1986; 1 (2): 69-73
  • ETHANOL-PRODUCTION BY NITROGEN-DEFICIENT YEAST-CELLS IMMOBILIZED IN A HOLLOW-FIBER MEMBRANE BIOREACTOR APPLIED MICROBIOLOGY AND BIOTECHNOLOGY INLOES, D. S., Michaels, A. S., Robertson, C. R., Matin, A. 1985; 23 (2): 85-91
  • EFFECT OF ANTECEDENT GROWTH-CONDITIONS ON SENSITIVITY OF ESCHERICHIA-COLI TO PHENYLPHENOL FEMS MICROBIOLOGY LETTERS ABOUSHLEIB, H., Berg, J. D., Matin, A. 1983; 19 (2-3): 183-186
  • THE PROTONMOTIVE FORCE AND THE DELTA-PH IN SPHEROPLASTS OF AN ACIDOPHILIC "BACTERIUM(THIOBACILLUS-ACIDOPHILUS) JOURNAL OF GENERAL MICROBIOLOGY Matin, A., Matin, M. 1982; 128 (DEC): 3071-3075
  • GROWTH-FACTOR REQUIREMENT OF THIOBACILLUS-NOVELLUS ARCHIVES OF MICROBIOLOGY Matin, A., KAHAN, F. J., LEEFELDT, R. H. 1980; 124 (1): 91-95
  • MICROBIAL SELECTION IN CONTINUOUS CULTURE JOURNAL OF APPLIED BACTERIOLOGY Harder, W., Kuenen, J. G., Matin, A. 1977; 43 (1): 1-24

Conference Proceedings


  • USE OF BACTERIAL STRESS PROMOTERS TO INDUCE BIODEGRADATION UNDER CONDITIONS OF ENVIRONMENTAL-STRESS Little, C. D., Fraley, C. D., McCann, M. P., Matin, A. BUTTERWORTH-HEINEMANN. 1991: 493-498

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