Metagenomic insights into strategies of carbon conservation and unusual sulfur biogeochemistry in a hypersaline Antarctic lake

• Published in: The ISME Journal
• Main Authors: Yau, S, Lauro, FM, Williams, TJ, DeMaere, MZ, Brown, MV, Rich, J, Gibson, JAE, Cavicchioli, R
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group 2013
• Subjects: Biological Sciences; Genetics; Population; Ecological and Evolutionary Genetics; Antarctic; Organic Lake; Vestfold; Vestfold Hills; Antarc*; Antarctica
• Online Access: https://doi.org/10.1038/ismej.2013.69; http://www.ncbi.nlm.nih.gov/pubmed/23619305; http://ecite.utas.edu.au/88991

Organic Lake is a shallow, marine-derived hypersaline lake in the Vestfold Hills, Antarctica that hasthe highest reported concentration of dimethylsulfide (DMS) in a natural body of water. To determinethe composition and functional potential of the microbial community and learn about the unusualsulfur chemistry in Organic Lake, shotgun metagenomics was performed on size-fractionatedsamples collected along a depth profile. Eucaryal phytoflagellates were the main photosyntheticorganisms. Bacteria were dominated by the globally distributed heterotrophic taxa Marinobacter,Roseovarius and Psychroflexus. The dominance of heterotrophic degradation, coupled withlow fixation potential, indicates possible net carbon loss. However, abundant marker genes foraerobic anoxygenic phototrophy, sulfur oxidation, rhodopsins and CO oxidation were also linkedto the dominant heterotrophic bacteria, and indicate the use of photo- and lithoheterotrophy asmechanisms for conserving organic carbon. Similarly, a high genetic potential for the recycling ofnitrogen compounds likely functions to retain fixed nitrogen in the lake. Dimethylsulfoniopropionate(DMSP) lyase genes were abundant, indicating that DMSP is a significant carbon and energy source.Unlike marine environments, DMSP demethylases were less abundant, indicating that DMSPcleavage is the likely source of high DMS concentration. DMSP cleavage, carbon mixotrophy(photoheterotrophy and lithoheterotrophy) and nitrogen remineralization by dominant Organic Lakebacteria are potentially important adaptations to nutrient constraints. In particular, carbonmixotrophy relieves the extent of carbon oxidation for energy production, allowing more carbonto be used for biosynthetic processes. The study sheds light on how the microbial community hasadapted to this unique Antarctic lake environment.