Additional Participants

Graduate Student

Yvette Luyten

Nitin Nair

Project Period

September 2002-August 2006

Level of Access

Open-Access Report

Grant Number


Submission Date



Environmental genomics, wherein the total genomic diversity of a natural community may be sampled and analyzed in an ecological context, remains an elusive goal. This is due, at least in part, to (I) a lack of reliable estimates of total community diversity and (II) a lack of information regarding the exact phylogenetic, genomic and ecological units measured by commonly used diversity estimators. Although ribosomal RNA approaches have provided the first steps towards diversity estimation, and are widely used as a proxy for unique bacterial types in natural populations, the genomic unit a ribotype measures remains largely unexplored. It is generally believed that ribotype is a poor indicator of ecotype because its slow molecular clock does not track many other genomic changes that are significant with respect to physiological functions and ecological roles. Further, there are reasons to believe microbes in typical natural environments encounter forces much different from those that shape genome evolution among the cultivated opportunists and pathogens that predominate in genomic studies.

This project is using an approach that will allow the systematic sampling of environmental genomes by capturing large gene fragments anchored to ribosomal genes (the current standard biomarker for diversity estimation) as well as methods by which this approach can be extended to reassembling larger genome regions of uncultivated bacteria. The goals of this investigation are: 1) to estimate total ribotype diversity in a coastal marine environment taking into account new developments in understanding of PCR artifacts and new statistical approaches toward estimating sampling coverage, 2) to explore the relationship of ribotype diversity to genome diversity by sampling sequences contiguous to rRNA genes in abundant ribotypes, 3) to explore the mechanisms that may contribute to shaping genomes in natural communities, and 4) to continue development of methods to automate and extend the reach of genomic research in natural communities. This research will provide (I) boundaries for bacterial diversity estimates in the environment and (II) insights into how processes that are important in shaping the structure and dynamics of microbial communities may also be influential in shaping the evolution of microbial genomes.

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