Metagenomic insights into microbial community control: From the global to the microscale.
The recent application of next-generation DNA sequencing tools has provided a wealth of new information about the diversity of microbial life, however the ecological factors which determine spatial patterns in prokaryotic gene abundance remain elusive. Using metagenomics and high-throughput sequencing of taxonomic marker genes, we have demonstrated shifts in microbial taxonomy and function along a salinity and nutrient gradient in the Coorong lagoon, South Australia. Functionally, genes showing the greatest response to physiochemical variability are related to salinity tolerance and photosynthesis. Taxonomically, Cyanobacteria and Archaea showed the greatest shifts in abundance along the gradient. Despite this variability however, the overall signature of metagenomic profiles remained remarkably conserved between sampling sites, and when compared to metagenomes from diverse habitats clustered with diverse sediment and soil habitats, regardless of salinity. This data indicates that the substrate type of the sample, fluid or porous, is a fundamental determinant of patterns in microbial community function globally, regardless of local chemical conditions. Whilst microbial community structure is determined on varying global and local scales, as demonstrated by the above data, the behaviour of microorganisms is determined on the microscale, with individual cells responding to gradients in specific nutrients in a patchy ecosystem. Using novel in situ sampling devices, and next-generation DNA sequencing techniques, our future work will focus on describing the microscale interactions between cells and nutrients in the ocean and how this relationship relates to ocean scale biogeochemical processes within the Carbon, Nitrogen and Sulfur cycles.