2008 Annual Science Report
Marine Biological Laboratory Reporting | JUL 2007 – JUN 2008
Describing the Anaerobic Thermophilic Microbial Community: A Metagenomic Strategy
The ocean is one of the least explored parts of the microbial world, including at deep-sea hydrothermal vents, where the unique geochemistry creates many habitats for microbial and animal communities. These organisms encounter many conditions that we humans consider too extreme- too hot, too toxic, too little oxygen- but microbes seem to find a way and continue to push the limits of life. An impetus for studying life at deep-sea hydrothermal vents is that life may have originated and evolved near hydrothermal systems, and that organisms currently living in these likely analogues of early habitats may still harbor characteristics of early life. In addition, microbes unique to the hydrothermal vents could provide insight into metabolic processes, strategies for growth, and survival of life on solar bodies with a water history, such as Mars and Jupiter’s moon Europa. Our research on diffuse flow vents at deep-sea hydrothermal seamounts provides insight into the diversity, physiology, and genetic potential of these unique microbial communities within the context of their dynamic and complex geochemical habitat.
Our October 2007 publication in Science represents the most exhaustive survey to date of microbial population structure in any single habitat. It provides what may be the first example of a comparative population structure analysis with statistically significant descriptions of diversity, richness, and distribution of microbial communities. Our results show that the richness and diversity of microbial communities must be considered more carefully in experimental design to properly evaluate and determine the inventory of metabolic capacity in an ecosystem. In addition to resolving with unprecedented detail the fine-scale variation within and between microbial communities, and the extreme complexity of the rare biosphere at deep-sea hydrothermal vents, it shows that diversity at all phylogenetic depths can vary in response to different chemical environments at sites within close proximity. The paper also demonstrates that it is now possible to step beyond descriptions of microbial diversity by including estimates of evenness and richness in ecological studies of microbial populations. These measures are essential for comprehending how different microbial populations in a community impact overall function. This approach to studying microbial ecology represents a substantial advance in our understanding of microbial life on Earth. In addition, we carried out experiments that show the size of the PCR amplicon must be considered carefully in experimental design to properly evaluate and determine the microbial diversity and community structure in a mixed sample. The results of this study have important implications for molecular studies of microbial communities in all habitats. While sequencing large portions of the SSU rRNA gene is essential for detailed phylogenetic analysis, long amplicons are not always the most appropriate tool for measuring total community diversity or taxonomic membership. Regardless of sequencing technology used, the primer set used and amplicon size must be considered when designing appropriate experiments. This work is in review at Environmental Microbiology.
PROJECT MEMBERS:Julie Huber
RELATED OBJECTIVES:Objective 4.1
Earth's early biosphere
Environment-dependent, molecular evolution in microorganisms
Co-evolution of microbial communities