The role of planktonic F lavobacteria in processing algal organic matter in coastal E ast A ntarctica revealed using metagenomics and metaproteomics

Abstract

Summary Heterotrophic marine bacteria play key roles in remineralizing organic matter generated from primary production. However, far more is known about which groups are dominant than about the cellular processes they perform in order to become dominant. In the S outhern O cean, eukaryotic phytoplankton are the dominant primary producers. In this study we used metagenomics and metaproteomics to determine how the dominant bacterial and archaeal plankton processed bloom material. We examined the microbial community composition in 14 metagenomes and found that the relative abundance of F lavobacteria (dominated by P olaribacter ) was positively correlated with chlorophyll a fluorescence, and the relative abundance of SAR 11 was inversely correlated with both fluorescence and F lavobacteria abundance. By performing metaproteomics on the sample with the highest relative abundance of F lavobacteria ( N ewcomb B ay, E ast A ntarctica) we defined how F lavobacteria attach to and degrade diverse complex organic material, how they make labile compounds available to A lphaproteobacteria (especially SAR 11) and G ammaproteobacteria , and how these heterotrophic Proteobacteria target and utilize these nutrients. The presence of methylotrophic proteins for archaea and bacteria also indicated the importance of metabolic specialists. Overall, the study provides functional data for the microbial mechanisms of nutrient cycling at the surface of the coastal S outhern O cean.

Bibliographic Information