Microbial Population Structures in the Deep Marine Biosphere

TLDR

Environmental DNA sequencing can model microbial ecosystems only when population structure—diversity and evenness—is accurately assessed. The study examined population structure at two hydrothermal vents using over 900,000 small‑subunit rRNA amplicons and predicts that hundreds of thousands of sequences are needed to capture the vast microbial diversity and that evenness patterns of both abundant and rare taxa may shape ecosystem dynamics. The authors analyzed more than 900,000 microbial small‑subunit rRNA amplicons from two neighboring hydrothermal vents to assess diversity and evenness. The vent communities differ in population structure reflecting local geochemistry, with archaeal diversity nearly exhaustive but bacterial diversity still increasing at every taxonomic level.

Abstract

The analytical power of environmental DNA sequences for modeling microbial ecosystems depends on accurate assessments of population structure, including diversity (richness) and relative abundance (evenness). We investigated both aspects of population structure for microbial communities at two neighboring hydrothermal vents by examining the sequences of more than 900,000 microbial small-subunit ribosomal RNA amplicons. The two vent communities have different population structures that reflect local geochemical regimes. Descriptions of archaeal diversity were nearly exhaustive, but despite collecting an unparalleled number of sequences, statistical analyses indicated additional bacterial diversity at every taxonomic level. We predict that hundreds of thousands of sequences will be necessary to capture the vast diversity of microbial communities, and that different patterns of evenness for both high- and low-abundance taxa may be important in defining microbial ecosystem dynamics.