1. Microbial community structure and photoheterotrophic activity across different Australian oceanic environments oceanic environments
Investigator
PhD Candidate Jaume Bibiloni Isaksson
Supervisors
Dr. Justin Seymour – C3 Plant Functional Biology and Climate Change Cluster, UTS
Dr. Mark Brown School of Biotechnology and Biomolecular Sciences, UNSW

2. D. J. Des Marais
Science, 8 September 2000

3. Classification of Phototrophic Organisms

4. http://www. seagrant. umn

5. Photoheterotrophic bacteria
Proteorhodopsin bacteria (PRB) contains proteorhodopsin
Aerobic anoxygenic phototrophic bacteria (AAnPB) contains bacteriochlorophyll a

6. Proteorhodopsin
Proteorhodopsin (PR) are retinal-binding integral membrane proteins belonging to the rhodopsin superfamily
Fig. 2 Secondary structure of proteorhodopsin. Béjà et al. (2000)

7. Proteorhodopsin
PR is a light-driven proton pump that may enhance ATP production by heterotrophic bacteria that otherwise rely on organic material oxidation for energy.
A single amino acid substitution in PR protein sequence bacteria absorb different wavelengths of light: 490 nm (blue) to 520 nm (green)
Fig. 3 Proteorhodopsin and possible relation to proton pumping (Walter et al., 2007)

8. Bacteriochlorophyll a

9. Aerobic Anoxygenic Photoheterotrophs

10. Why are photoheterotrophs important?

11. PR genes have been identified in a wide variety of cultured and uncultured bacterioplankton, such as α and γ-Proteobacteria, Flavobacteria, Actinobacteria, and Archaea.
PR in Pelagibacter ubique, a cultured representative, the most abundant bacterial group inhabiting the upper ocean marine, clades SAR11
up to 70% of the bacteria in the Sargasso Sea
7 to 57% North Atlantic Ocean Contain PR
13% of the bacteria in the Mediterranean Sea

12. AAnPB have been identified in a wide variety of cultured and uncultured bacterioplankton, such as α, β, and γ-Proteobacteria.
Roseobacter group belong to AAnPB, a cultured representative, 1 in 5 bacteria cells inhabiting coastal waters.
Also important in DMSP degradation (cleavage/demethylation). Results liberation of climate-influencing dimethyl sulfide, thus key in marine sulfur cycle.
(not all Roseobacter synthesize Bchla).
~ 10 to 20 in mesotrophic estuaries
positively correlate with Chla in variety of environments AAnPB
up to 25% in hyperoligotrophic South Pacific Ocean

13. Both AAnBP and PRB are incapable of photoautotrophy (do not have enzyme RubisCO) and rely on heterotrophy of their cellular energetics
Sunlight provide additional energy to cell, reducing the need for respiratory oxidation of organic substrates
The ability to use light energy seems to allow more economical utilization of dissolved organic matter, thus photoheterotrophic bacteria may play a unique role in the microbial carbon pump (MCP).

18. 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 condition

19. Hypotheses
H1: PR and AAnBP diversity, abundance and activity will vary throughout the sample period/location, since significant physicochemical changes in seawater will provide more suitable conditions for different types of bacteria
H2: PR-bearing bacteria abundance will become more abundant during summer (Austral) period, since PR bearing bacteria may help to provide energetic and physiological advantages under in more oligotrophic conditions

20. Experimental procedures
Sampling and environmental parameters
Monthly samples (surface samples)
Port Hacking Mooring (IMOS platform) ( ) Temporally.
Maria Island, Port Hacking, Stradbroke Mooring stations (2012) Spatially/temporally
Data is available via the IMOS portal
Future sampling (different depths)
North Australia research voyage (July 2013) Spatially
East Australian current research voyage (April 2014) Spatially
South Australia research voyage (Sept 2014) Spatially
Environmental data will be collected in situ.

21. Broome
Stradbroke
Brisbane
Freemantle
Sydney
Port Hacking
Tasmania
Maria Island

22. Experimental procedures
Molecular experiments
DNA/RNA extraction (Standards Kit extraction)
PCR amplification of 16S rRNA, PR and pufM genes
454/Illumina pyrosequencing of 16S rRNA, PR and pufM genes to assess diversity
Determination of ratios of 16S rRNA (all bacteria, SAR11 clade) and PR (SAR11 clade, Flavobacteria) and pufM gene abundance/expression via real-time quantitative PCR
Screen for PR and Bchla genes in seawater isolates

23. Data Analysis 454/Illumina pyrosequencing data with QIIME
Relationship between abundance, diversity and physicochemical parameters using PERMANOVA in PRIMER+
PR/pufM sequence compilations and analysis using ARB software
Network analysis
Data Analysis

24. Two major questions to be answer in this project
How do Australian marine microbial communities (i.e. photoheterotrophs) and their biogeochemical function vary in space and time?
Will shifting ocean circulation patterns alter microbial community structure and function in ways that will have potential feed-back effects on ecosystem stability?

25. People in our Lab
Dr Justin Seymour - Leader and supervisor
Dr Mark Brown – Co-supervisor (UNSW)
Dr Tom Jeffries - Post-doc
Lauren Messer - PhD student
Project is funding by an ARC grant from Australia government