PT  - JOURNAL ARTICLE
AU  - Jasmine S. Berg
AU  - Petra Pjevac
AU  - Tobias Sommer
AU  - Caroline R.T. Buckner
AU  - Miriam Philippi
AU  - Philipp F. Hach
AU  - Manuel Liebeke
AU  - Moritz Holtappels
AU  - Francesco Danza
AU  - Mauro Tonolla
AU  - Anupam Sengupta
AU  - Carsten J. Schubert
AU  - Jana Milucka
AU  - Marcel M.M. Kuypers
TI  - Dark aerobic sulfide oxidation by anoxygenic phototrophs in the anoxic waters of Lake Cadagno
AID  - 10.1101/487272
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 487272
4099  - http://biorxiv.org/content/early/2018/12/06/487272.short
4100  - http://biorxiv.org/content/early/2018/12/06/487272.full
AB  - This study reveals that sulfide oxidation within an anoxic layer of purple sulfur bacteria in the stratified water column of Lake Cadagno is largely coupled to oxygen consumption. Our findings imply that aerobic metabolism may be more prevalent in anoxic zones than previously thought. We also present a metagenome-assembled genome of Chromatium okenii which is the first genome sequence for the genus Chromatium and reveals new interesting physiological features of this environmentally relevant organism including its capacity for aerobic respiration.SUMMARY Anoxygenic phototrophic sulfide oxidation by purple and green sulfur bacteria plays a key role in sulfide removal from anoxic shallow sediments and stratified waters. Although some purple sulfur bacteria can also oxidize sulfide with nitrate and oxygen, little is known about the prevalence of this chemolithotrophic lifestyle in the environment. In this study, we investigated the role of Chromatium okenii in chemolithotrophic sulfide removal in the chemocline of Lake Cadagno. This purple sulfur bacterium appears to remain active during the night, as evidenced by its continued motility and O2-driven carbon fixation. Our temporally resolved, high-resolution chemical profiles revealed that sulfide oxidation is largely driven by aerobic respiration in the anoxic chemocline. We postulate that the abundant and highly active Chr. okenii are, at least in part, responsible for this aerobic sulfide oxidation and that they bridge the spatially separated gradients of oxygen and sulfide using a novel mechanism of transport driven by the strong convection within the chemocline. The genome of Chr. okenii reconstructed from the Lake Cadagno metagenome confirms its capacity for microaerophilic growth and provides further insights into its metabolic capabilities. Altogether, our observations suggest that aerobic respiration may not only play an underappreciated role in anoxic environments, but also that organisms typically considered strict anaerobes may be involved.