A Microbial Biorealm page on the genus Roseobacter denitrificans
Higher order taxa
Bacteria, Proteobacteria, Alphaproteobacteria, Rhodobacterales, Rhodobacteraceae, Roseobacter
Roseobacter denitrificans sp. OCh114 (previously called Erythrobacter sp. OCh114)
Description and significance
Roseobacter denitrificans is a purple aerobic anyoxygenic phototrophic (AAP) bacterium that dwells free-living in lakes and ocean surface waters, soils and even near deep sea hydrothermal vents. It was isolated from the surfaces of green seaweeds of the coastal marine sediments in Australia. Members of the Roseobacter clade are widespread and abundant in such marine environments, having diverse metabolisms. The purple proteobacteria in particular, are the only known organisms to capture light energy to enhance growth requiring the presence of oxygen yet do not produce oxygen themselves. The highly adaptive AAPs compose more than 10% of the microbial community in some euphotic upper ocean waters and are potentially major contributors to the fixation of the greenhouse gas CO2. The marine AAP species R. denitrificans grows not only photoheterotrophically in the presence of oxygen and light but also anaerobically in the dark using nitrate or trimethylamine N-oxide as an electron acceptor. It is the most studied AAP for this reason and is one of the main model organisms to study aerobic phototrophic bacteria.
The importances of the bacterium's genome sequence are for the following reasons: 1) The evolutionary genesis of photosynthesis genes-it is a marine bacterium, and so may be representative of the globally huge population of aerobic phototrophic bacteria and could help narrow the true evolutionary position of the aerobic phototrophic bacteria by whole genome comparisons (Kolber et al. 2001) ; 2) Pathways of carbon dioxide fixation and production it is the only aerobic phototrophic bacterium that is capable of anaerobic growth, by use of nitrate as a terminal electron acceptor (Yurkov and Beatty 1998) , which will facilitate subsequent studies of the effects of oxygen on photosynthetic and other metabolic processes; 3) the work on respiratory and photosynthetic electron transfer pathways in this organism has established this species as the model aerobic phototrophic bacterium (Candela et al. 2001; Okamura et al. 1986; Schwarze et al. 2000)
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
The genome sequence of Roseobacter denitrificans was completed in 2006 by a team in Arizona State University.
The genome lacks genes that code for known photosynthetic carbon fixation pathways, with most notably missing the genes for Calvin cycle enzymes ribulose bisphosphate carboxylase (RuBisCO) and phosphoribukolkinase.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Circular representation of the Roseobacter denitrificans OCh 114 chromosome.
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
There are no known pathological effects of this bacterium on humans.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
1) (Fleischman and Kramer 1998; Yurkov and Beatty 1998; Yurkova et al. 2002)
2) Swingley W.D., Sadekar S., Mastrian S.D., Matthies H.J., Hao J., Ramos H., Acharya C.R., Conrad A.L., Taylor H.L., Dejesa L.C., Shah M.K., O'Huallachain M.E., Lince M.T., Blankenship R.E., Beatty J.T., Touchman J.W. ; "The complete genome sequence of Roseobacter denitrificans reveals a mixotrophic rather than photosynthetic metabolism"; J. Bacteriol. 189:683-690 (2007)
3) Candela, M., E. Zaccherini, and D. Zannoni. 2001. Respiratory electron transport and light-induced energy transduction in membranes from the aerobic photosynthetic bacterium Roseobacter denitrificans. Arch. Microbiol. 175:168-177
Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.
Edited by student of Rachel Larsen