PT  - JOURNAL ARTICLE
AU  - Petra Pjevac
AU  - Stefan Dyksma
AU  - Tobias Goldhammer
AU  - Izabela Mujakić
AU  - Michal Koblížek
AU  - Marc Mussmann
AU  - Rudolf Amann
AU  - Sandi Orlić
TI  - <em>In situ</em> abundance and carbon fixation activity of distinct anoxygenic phototrophs in the stratified seawater lake Rogoznica
AID  - 10.1101/631366
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 631366
4099  - http://biorxiv.org/content/early/2019/05/08/631366.short
4100  - http://biorxiv.org/content/early/2019/05/08/631366.full
AB  - Sulfide-driven anoxygenic photosynthesis is an ancient microbial metabolism that contributes significantly to inorganic carbon fixation in stratified, sulfidic water bodies. Methods commonly applied to quantify inorganic carbon fixation by anoxygenic phototrophs, however, cannot resolve the contributions of distinct microbial populations to the overall process. We implemented a straightforward workflow, consisting of radioisotope labeling and flow cytometric cell sorting based on the distinct autofluorescence of bacterial photo pigments, to discriminate and quantify contributions of co-occurring anoxygenic phototrophic populations to in situ inorganic carbon fixation in environmental samples. This allowed us to assign 89.3 ±7.6% of daytime inorganic carbon fixation by anoxygenic phototrophs in Lake Rogoznica (Croatia) to an abundant chemocline-dwelling population of green sulfur bacteria (dominated by Chlorobium phaeobacteroides), whereas the co-occurring purple sulfur bacteria (Halochromatium sp.) contributed only 1.8 ±1.4%. Furthermore, we obtained two metagenome assembled genomes of green sulfur bacteria and one of a purple sulfur bacterium which provides the first genomic insights into the genus Halochromatium, confirming its high metabolic flexibility and physiological potential for mixo-and heterotrophic growth.