Project title: Changes in microbial community structure and photoheterotrophic activity across different Australian oceanic environments
Supervisors: Dr Justin Seymour (C3 UTS), Dr Mark Brown (UNSW)
PhD conferred: 2017
Marine microbes carry out essential metabolic processes, such as transformation of elements, degradation of organic matter and recycling of nutrients, to support and maintain all marine life. These marine microbes use a wide variety of metabolic strategies to gain energy from their environment. One important strategy is photoheterotrophy. Photoheterotrophic bacteria can make up large fractions of marine microbial communities and include Aerobic anoxygenic phototrophic bacteria (AAnPB)1 and proteorhodopsin bacteria (PRB)2,3. AAnPB contain bacteriochlorophyll a, which is used for photosynthesis and PRB contain proteorhodopsin, a very simple form of biological light-harvesting mechanism, which provides energy for the cell. These two groups are considered photoheterotrophs. Although their unique metabolisms play a central role in ocean biogeochemistry, we currently know very little about their dynamics within the Australian marine environment.
Observational and modeling studies have shown that key Australian oceanographic provinces have experienced changes in circulation patterns, as a result of climate change. For instance, there has been a marked increase in the strength of the East Australian Current. This study aims to investigate spatial and temporal patterns in the distribution of photoheterotrophic bacteria in key Australian marine environments.
Aims and Objectives: This project will use modern molecular methods such as the next generation sequencing (454 and Illumina platforms), real-time polymerase chain reaction techniques, and bioinformatics to investigate whether proteorhodopsin (PR) and bacteriochlorophyll a (Bchla) gene abundance, distribution and transcriptional activity change both spatially and temporally across different key Australian oceanographic regions: East Australian Current (EAC), The Leeuwin Current (LC), The Tasman Sea (TS) and Southern Australian Shelf Waters (SASW), which are currently being influenced by climate change. The project will have four key scientific objectives:
i) Identify major bacteria and archaea groups including PR and Bchla groups
ii) Estimate the ratio of PR and Bchla genes expression and abundance to bacterial populations
iii) Examine how the abundance, diversity and activity of different PR and Bchla types varies temporally in different oceanographic coastal region, which are suffering from the impacts of climate change
iv) Perform laboratory growth experiments to test the dynamics of photoheterotrophy under different light and nutrient conditions
1. Kolber, Z. S., C. L. Van Dover, R. A. Niederman, and P. G. Falkowski (2000). Bacterial photosynthesis in surface waters of the open ocean, Nature, 407, 177-179.
2. Béjà, O., L. Aravind, E. V. Koonin, M. T. Suzuki, A. Hadd, L. P. Nguyen, S. B. Jovanovich, C. M. Gates, R. A. Feldman, J. L. Spudich, E.N. Spudich, and E. F. DeLong (2000). Bacterial rhodopsin: Evidence for a new type of phototrophy in the Sea, Science, 289, 1902-1906.
3. Béjà, O., Spudich. E. N., Spudich, J. L., Leclerc, M., and DeLong, E. F. (2001). Proteorhodopsin phototrophy in the ocean, Nature, 411,786–789.
4. Ridgway, K.R. (2007). Seasonal circulation around Tasmania: an interface between eastern and western boundary dynamics. Journal of Geophysical Research, 112, C10016.