MPI Seminars

Abstract

Microbial communities exhibit long-tail distributions in which very high-frequency populations precede low-frequency populations that gradually "tail off" asymptotically. For microbes and other biological forms, the long tail corresponds to a “rare biosphere” composed of many low abundance taxa. The International Census of Marine Microbes first described a “rare biosphere” that accounts for an estimated 500,000 kinds of microbes contained within less than one part out of 1018 parts of the world’s oceans. New algorithms capable of discriminating between closely related taxa show that the sheer size of the microbial “rare biosphere” may be much greater than previously reported. The recently introduced techniques of oligotyping and minimum entropy decomposition permit the description of microbial diversity at finer scales for closely related but subtly distinct 16S rRNA gene amplicon sequences that represent distinct genomes in a microbial community. These analytical paradigms take advantage of Shannon entropy calculations to identify information rich nucleotide positions that differentiate between closely related taxa within the same genus. When applied to studies of microbial communities in aquatic, marine and human microbiomes, we detect increased diversity and identify ecologically important differences between closely related taxa. Yet high-resolution analyses of marker genes lack resolving power necessary to describe genome dynamics associated with response of microbial populations to ecological change. The combination of shotgun metagenomic sequencing, assembly into genome bins and cultivar genomics provides insights into the transition of host associated microbes into potential pathobionts in response to inflammation and antibiotic stress in the human gut.