Relman Lab Research Projects

Resilience in the Human Microbiome

Maintenance and recovery of key beneficial services by complex microbial communities in the face of disturbance is fundamental to health.  Yet, stability and resilience vary in, and between different individuals, and are poorly understood.  We seek to identify features of the human microbiome that predict microbial community stability and resilience following disturbance. 

Pregnancy and the Human Microbiome

Normal pregnancy represents a unique, transient, and dynamic state of altered anatomy, physiology, and immune function. Preterm birth, i.e., before 37 weeks of gestation, occurs in approximately 11% of pregnancies and is the leading cause of neonatal death. In both term and preterm pregnancies, the interplay between the microbiota and the host remains poorly understood. The human indigenous microbial communities (microbiota) play critical roles in health and may be especially important for mother and fetus during pregnancy. We are interested in understanding how the microbiome helps to shape maternal health and fetal development during pregnancy, and how pregnancy shapes the microbiome. 

The Microbiome in Early Childhood

Thought to be essentially sterile in utero, the human body is rapidly colonized by a range of microbes immediately following birth. These relatively simple microbial communities grow in complexity and differentiate until they reach an adult-like configuration around three years of age. These microbes participate in many complex physiological and immunological processes, such as aiding in digestion, directing immune system development, and excluding pathogens. This process of microbiome maturation is not well understood, but can be crucial for the establishment of a “healthy” microbiome.

Human Oral Microbial Communities in States of Hyposalivation 

Landscape ecology examines the relationships between the spatial arrangement of different landforms and the processes that give rise to spatial and temporal patterns in local community structure. The spatial ecology of the microbial communities that inhabit the human body—and in particular, those of the mouth—deserve greater attention. Important questions include what defines the size of a population (i.e., ‘‘patch’’) in a given body site, what defines the boundaries of distinct patches within a single body site, what are the factors that explain boundaries, population composition, and patterns across populations, and where and over what spatial scales within a body site are gradients detected.

Microbial Diversity in Marine Mammals

Marine mammals play crucial roles in the ecology of our oceans. They serve as apex predators and keystone species in the food web, influence marine nutrient storage and recycling, and are important indicators of ocean health. Their evolutionary history suggests multiple independent returns from land and adaptations to life in the sea. These intelligent animals also have economic value due to their aesthetic and intrinsic value to humans.  Despite their importance, little is known about the indigenous microbiota of marine mammals.

Arsenic and the Human Microbiome

Arsenic (As) contamination of soils and water occurs worldwide-including in the U.S.-originating from both environmental and anthropogenic sources. Naturally-occurring alluvial As contaminates groundwater in South and Southeast Asia, and has caused wide-scale poisoning of a susceptible and malnourished populace. Chronic As exposure affects over 25 million people in Bangladesh alone. Industrial sources of arsenic-e.g., arsenic-containing pesticides in agriculture-also contribute to global exposure. In the United States, As tops the hazardous substance priority list of the Agency for Toxic Substances and Disease Registries, and 13 million Americans are exposed to levels exceeding the US Water Quality Standards. 

Genomics and Diagnosis of Fever

We are using host gene expression patterns and cell-free DNA and RNA in blood to classify and diagnose systemic infections. Specific diagnosis and management of infection is often complicated by our inability to culture most microorganisms, and the need to develop new reagents for each additional pathogen. Host transcript abundance patterns represent a conserved set of "reagents" that can be efficiently measured on a genome-wide basis. 

Lactose Intolerance and the Human Microbiome

This study will examine changes to the composition of the microbiome that occur in response to eating or avoiding dairy products, and the time course of such changes. We hypothesize that certain bacterial species in the gut microbiome are associated with acquired lactose tolerance: they allow hosts to eat dairy products without suffering the negative outcomes characteristic of lactose intolerance. We further hypothesize that regularly eating dairy products is necessary for the persistence of a lactose tolerance in most individuals, with dairy acting as a prebiotic to support the populations of lactose-utilizing, tolerance-associated bacteria. If these hypotheses are correct, our study may support informed consumption of dairy products in lactose intolerant individuals; it would allow them to develop and maintain lactose tolerance and to reap the potential health benefits of dairy, e.g. those related to the uptake of calcium.