Proteorhodospin-bearing bacteria in Antarctic sea ice

• Published in: Applied and Environmental Microbiology
• Main Authors: Koh, EY, Atamna-Ismaeel, N, Martin, AR, Cowie, ROM, Beja, O, Davy, SK, Maas, EW, Ryan, KG
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Soc Microbiology 2010
• Subjects: Biological Sciences; Microbiology; Microbial Ecology; Antarctic; Ross Sea; Antarc*; Sea ice
• Online Access: http://aem.asm.org/cgi/content/abstract/76/17/5918; https://doi.org/10.1128/AEM.00562-10; http://www.ncbi.nlm.nih.gov/pubmed/20601510; http://ecite.utas.edu.au/68331

Proteorhodopsins (PRs) are widespread bacterial integral membrane proteins that function as light-drivenproton pumps. Antarctic sea ice supports a complex community of autotrophic algae, heterotrophic bacteria,viruses, and protists that are an important food source for higher trophic levels in ice-covered regions of theSouthern Ocean. Here, we present the first report of PR-bearing bacteria, both dormant and active, inAntarctic sea ice from a series of sites in the Ross Sea using gene-specific primers. Positive PR sequences weregenerated from genomic DNA at all depths in sea ice, and these sequences aligned with the classes Alphaproteobacteria,Gammaproteobacteria, and Flavobacteria. The sequences showed some similarity to previouslyreported PR sequences, although most of the sequences were generally distinct. Positive PR sequences werealso observed from cDNA reverse transcribed from RNA isolated from sea ice samples. This finding indicatesthat these sequences were generated from metabolically active cells and suggests that the PR gene is functionalwithin sea ice. Both blue-absorbing and green-absorbing forms of PRs were detected, and only a limitednumber of blue-absorbing forms were found and were in the midsection of the sea ice profile in this study.Questions still remain regarding the proteins ecological functions, and ultimately, field experiments will beneeded to establish the ecological and functional role of PRs in the sea ice ecosystem.