AUTHOR=Diao Muhe , Sinnige Ruben , Kalbitz Karsten , Huisman Jef , Muyzer Gerard 

TITLE=Succession of Bacterial Communities in a Seasonally Stratified Lake with an Anoxic and Sulfidic Hypolimnion

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02511

DOI=10.3389/fmicb.2017.02511

ISSN=1664-302X

ABSTRACT=<p>Although bacteria play key roles in aquatic food webs and biogeochemical cycles, information on the seasonal succession of bacterial communities in lakes is still far from complete. Here, we report results of an integrative study on the successional trajectories of bacterial communities in a seasonally stratified lake with an anoxic hypolimnion. The bacterial community composition of epilimnion, metalimnion, and hypolimnion diverged during summer stratification and converged when the lake was mixed. In contrast, bacterial communities in the sediment remained relatively stable over the year. Phototrophic <italic>Cyanobacteria</italic> and heterotrophic <italic>Actinobacteria, Alphaproteobacteria</italic> and <italic>Planktomycetes</italic> were abundant in the aerobic epilimnion, <italic>Gammaproteobacteria</italic> (mainly <italic>Chromatiaceae</italic>) dominated in the metalimnion, and <italic>Chlorobi, Betaproteobacteria, Deltaproteobacteria</italic>, and <italic>Firmicutes</italic> were abundant in the anoxic sulfidic hypolimnion. Anoxic but nonsulfidic conditions expanded to the surface layer during fall turnover, when the epilimnion, metalimnion and upper hypolimnion mixed. During this period, phototrophic sulfur bacteria (<italic>Chromatiaceae</italic> and <italic>Chlorobi</italic>) disappeared, <italic>Polynucleobacter</italic> (<italic>Betaproteobacteria</italic>) and <italic>Methylobacter</italic> (<italic>Gammaproteobacteria</italic>) spread out from the former meta- and hypolimnion to the surface layer, and <italic>Epsilonproteobacteria</italic> dominated in the bottom water layer. <italic>Cyanobacteria</italic> and <italic>Planktomycetes</italic> regained dominance in early spring, after the oxygen concentration was restored by winter mixing. In total, these results show large spatio-temporal changes in bacterial community composition, especially during transitions from oxic to anoxic and from sulfidic to nonsulfidic conditions.</p>