In both natural and human-impacted environments, chemical conditions impact microbial community structures and functions. My research focuses on elucidating links between specific conditions and the structures/functions that they impact. During my PhD at the Université de Rennes 1, my research focused on the impacts of hydrological circulation and groundwater residence time on local geochemistry and residing groundwater microbial communities in three distant aquifers in Brittany (France). This study showed a geochemical compartmentalization of each aquifer reflecting the stark differences in groundwater residence time. The groundwater residence time was found to be strongly correlated with the type of microbial community structures observed, suggesting a strong influence of hydrological flowpaths on groundwater microbial communities. As Brittany is a region of intense agricultural activity, groundwater chemical conditions and microbial community structures in shallow groundwater were also largely impacted by these anthropogenic activities (e.g. pollution in nitrate). In this context, ecological function is tightly linked to community structure. However, that is not always the case, particularly when the function of interest is contained within mobile genetic elements. In my postdoctoral work in Northwestern University, I developed a new analytical strategy to predict the dissemination potential of antibiotic resistance genes based on metagenomic data and antimicrobial concentrations in dust. Using traditional microbiology techniques, I confirmed the predicted ability of antibiotic resistance genes to disseminate. Together, these studies have clarified our understanding of how specific chemical features of microbial habitats impact the structures and functions of the communities found therein.

Bio: Sarah obtained her bachelor’s degree in Biochemistry and Molecular Biology at the Universite de Rouen (France) in 2009.  She further pursued a master’s degree in Fundamental and Applied Microbiology at the University de Bretagne Occidentale (France), where she worked on the characterization of the cultivable microbial diversity in deep marine sediments, collected at the record depth of 2.2 km below the seafloor near the Canterbury Basin (New Zealand).  She graduated in 2011 and started her PhD in Earth Sciences at the Universite de Rennes 1 on the microbial diversity in aquifer groundwater.  During her PhD, she focused on the effects of hydrological circulation and agriculturally induced nitrate pollution in on groundwater microbial communities from three different aquifers in Brittany using a coupled metagenomic and geochemical approach.  In 2016, she graduated from her PhD and joined Dr. Erica Hartmann’s as a Postdoctoral fellow.  Sarah’s main interests rely on coupling of metagenomics and chemistry, microbial cultivation and bioinformatics.  During her postdoctoral work, collaboration with Dr. Ji-Ping Wang (Department of Statistics, Northwestern University) and Dr. Curtis Huttenhower (Department of Biostatistics, Harvard T.H. Chan School of Public Health).  Sarah investigated the dust microbiome from different indoor environments using metagenomics and bioinformatics.  Here, she determines how our daily use of antimicrobial compounds affects the presence, distribution and dissemination of antibiotic resistance genes in dust microbial communities.