Talk 1: VIRAL AND MICROBIAL COMMUNITY DYNAMICS IN FOUR AQUATIC ENVIRONMENTS Talk 2:CHARACTERIZATION OF ENVIRONMENTAL VIRAL DIVERSITY USING METAGENOMICS
TITLE:
Talk 1: VIRAL AND MICROBIAL COMMUNITY DYNAMICS IN FOUR AQUATIC ENVIRONMENTS
Talk 2:CHARACTERIZATION OF ENVIRONMENTAL VIRAL DIVERSITY USING METAGENOMICS
DATE:
Friday, October 9th, 2009
TIME:
3:30 PM
LOCATION:
GMCS 214
SPEAKER:
Speaker 1 : Beltran Rodriguez-Brito, PhD Student, CSRC
Speaker 2 : Florent Angly, PhD Student, CSRC
ABSTRACT:
Abstract 1:Background: The species composition and metabolic potential of microbial communities have been found to be predictable and stable for various particular ecosystems. This apparent stability contradicts both theoretical models and the viral-microbial dynamics observed in simple artificial systems, both of which suggest Kill-the-Winner behavior (i.e., rapid cycling of microbial taxa and their viral predators).
Methodology/Principal Findings: Microbial and viral metagenomes for analysis were obtained from four aquatic environments at various time points separated by one day to more than one year. Each environment exhibits a characteristic species composition and metabolic potential that is stable over time. In contrast, there are rapid changes at the fine-grained level of viral genotypes and microbial strains. Combined, these results suggest a model wherein the microbial and viral taxa are stable, but underlying this stability is a dynamic fluctuation of microbial strains and viral genotypes. This cycling of predator and prey populations is consistent with a Kill-the-Winner dynamic operating at the level of phage-sensitive microbial strains. The persisting top-ranked microbial taxa were the best predictors of each community’s metabolic capabilities. Even when the metabolic potentials of additional less-abundant taxa are included, such taxon-based predictions still miss some of the community metabolism recoverable by direct sampling of the metagenome.
Conclusions: In four aquatic environments, microbial and viral taxa persist over time while both populations are fluctuating in a Kill-the-Winner fashion at the level of viral genotypes and microbial strains. Thus, predator-prey dynamics coexist in this manner with stable and distinctive community metabolisms in these complex communities.
Abstract 2: Viruses and in particular phages, predators of Bacteria and Archaea, are numerically abundant in the environment and play important ecological roles. Yet, little is known about their diversity and distribution. The introduction of metagenomics has revolutionized the study of viral and microbial communities by bypassing the need to culture individual species, thus allowing access to their complete diversity. However, unlike for microorganisms, no standard technique exists to measure viral diversity from sequence data, and lab techniques are limiting. Computational methods were developed here to quantify the diversity of viruses from metagenomic data. These methods use overlapping sequences (contigs) assumed to come from the same species and are therefore robust to the large number of metagenomic sequences that cannot be assigned to a given species. The modeling of the contigs characterizes viral community structure, ?-diversity (sample diversity) and ?-diversity (change in diversity between samples). The implementation of a diversity workflow and its application to viral metagenomes from various biomes suggests that there may be as many as 10^8 viral species on Earth, and that their diversity patterns may be similar to that of microorganisms and macroorganisms.
HOST:
Forest Rohwer
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