Proteorhodopsins in Southern Ocean Bacteria

Metadata record for data from AAS Project 3127 See the link below for public details on this project. Bacteria in marine environments have been found to be able to partially support growth by using light to generate energy in a non-photosynthetic process. This is possible due to a special protein called proteorhodopsin. It is hypothesised that formation of proteorhodopsin has evolved to cope with extreme lack of nutrients. The goal is to determine the significance of proteorhodopsins in the productivity of Southern Ocean microbial communities. This includes determination of proteorhodopsin distribution, presence in seawater and sea-ice samples using molecular techniques, and determination of how important environmental factors (light, nutrient availability, temperature) may drive its synthesis and activity. Taken from the 2009-2010 Progress Report Project objectives: 1. Determine incidence of proteorhodopsins in Southern Ocean water and sea-ice derived bacteria (Year 1) and other Antarctic aquatic environments (Year 2 and 3). 2. Determine whether proteorhodopsins contribute to food web energy budgets. 3. Determine how proteorhodopsin contributions are influenced by physicochemical features of the environment including light availability, temperature and nutrients. Progress against objectives: Proteorhodopsin is a light harvesting membrane protein that has been found recently to occur in 30-70% of marine bacterial cells. The role of this protein is uncertain but believed to be highly important in energy and nutrient budgets in food webs as it is capable of generating a proton gradient. Amongst a cultured set of Antarctic bacteria we have discovered many PR-producing species. These include many Antarctic lake species. Research is ongoing to determine affect of light on the physiology of these bacteria in particular the genome sequenced species Psychroflexus torquis, an extremely cold-adapted resident of Antarctic sea-ice. 1. Completed screen of Antarctic bacterial collection for proteorhodopsin (PR) genes using PCR-based approaches 2. Proteomic-based analysis of PR-bearing sea-ice species Psychroflexus torquis is currently ongoing 3. Light/dark defined growth-based experiments determining conditions leading to biomass enhancement are ongoing