Rhodospirillum rubrum
A Microbial Biorealm page on the genus Rhodospirillum rubrum
Classification
Higher order taxa
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Alphaproteobacteria
Order: Rhodospirillales
Family: Rhodospirillaceae
Genus: Rhodospirillum
Species
Rhodospirillum rubrum
NEUF2011
Description and significance
Rhodospirillum rubrum is a Gram-negative, mesophilic proteobacteria. It has multi-layered outer envelopes, which contain mostly unsaturated, but some saturated fats in its cell wall. Its optimal growth temperature is 25-30 C. R. rubrum is a spirilla, meaning it has a spiral-shape. It is polarly flagellated, and therefore motile. Its length is 3-10 um, with a width of 08-1.0 um.
R. rubrum is a facultative anaerobe. It can undergo alcoholic fermentation or aerobic respiration. It contains carotenoid and bateriochlorophyll, found in its chromatophore particles, giving it its distinct purple-red color. The purple-red color is apparent under anaerobic conditions, while R. rubrum is colorless under aerobic conditions (i.e. photosynthesis). Carotenoids are found to help in light absorption during photosynthesis, and were discovered in investigation of R. rubrum's cytoplasmic membrane. Electron microscopy has revealed that the chromatopohore of R. rubrumis a flattened disk.
Although photosynthesis is active under aerobic conditions, it is generally suppressed in the presence of O2. Sulfur is a major byproduct of photosynthesis, not O2. With that said, R. rubrum can grow heterotrophically, or autotrophically when photosynthetic. It oxidizes carbon monoxide (CO), and can use sulfide at low concentrations as an electron donor in carbon dioxide reduction. Unlike many plants, R. rubrum contains no chlorophyll a (absorption spectra 430-662 nm). However, it does contain chlorophyll b (absorption spectra 660-680 nm) and bacteriochlorophylls (800-925 nm). This allows it to utilize more energy from the electromagnetic spectra.
R. rubrum is commonly found in mud, pond water, and sewage. It has not been found to infect humans or animals. It is a nitrogen fixing bacteria, which converts atmospheric nitrogen gas to ammonia: N2 –-(nitrogenase)--> NH4+.
There are several applications of R. rubrum in the field of biotechnology. It is a model system of light to chemical energy conversion and for its nitrogen fixing pathways. It is also the subject of radiation resistance studies. It can be used in several ways for consumption, as well. The proteobacteria may be a source of animal food and agricultural fertilizer. Another important role in research includes the production of vitamins. It is also being researched for its production of biological plastic from precursors of poly-hydroxy-butric-acid. R. rubrum may also be a contributor in biological hydrogen fuels, mainly through its evolution of the enzyme nitrogenase.
Genome structure
Finished Circular chromosome 4,352,825 base pairs 65% GC Plasmid 53,732 bp 60% GC Total 3,850 protein coding genes 83 RNA genes
Gene breakdown 6.9% Transcription 4.6% Translation, ribosome structure, biosynthesis 4.0% Replication, recombination and repair 7.9% Signal transduction mechanisms 5.9% Cell wall, membrane biogenesis 6.6% energy production and conversion 5.0% Carbohydrate transport and metabolism 9.9% Amino acid transport and metabolism 4.7% Coenzyme transport and metabolism 3.7% Lipid transport and metabolism 6.5% Inorganic ion transport and metabolism
Ecology
Rhodospirillum Rubrum is found in many natural environments such as pond water, mud, and sewage.
Cell structure and metabolism
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Basic Metabolism Versatile organism that can obtain energy through alternative mechanism.
Ex. Rhodospirillum can grow in dark chemo-tropical environment with the presence of O2 or they can grow in a photo-tropical environment without O2.
Phototrophically grown Rhodospirillum contain photosynthetic electron transport and ATP synthesis enzymes in their membrane and contain a membrane bound pyrophosphatase. Chemotrophically dark grown Rhodospirillum contain low concentration of bacteriochlorophyII and carotenoids and has no bound pyrophosphatase in their membrane.
Rhodospirillum Rubrum is found in many natural settings such as pond water, mud, or sewage.
Habitat; symbiosis; contributions to the environment.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Current Research
Some journal articles I found interesting.
1. Evidence that Ubiquinone Is a Required Intermediate for Rhodoquinone Biosynthesis in Rhodospirillum rubrum
2. Effect of Perturbation of ATP Level on the Activity and Regulation of Nitrogenase in Rhodospirillum rubrum
3. Modes of hydrogen production in the photosynthetic bacterium, Rhodospirillum rubrum
- Renewable energy
Cool Factor
Describe something you find "cool" about this microbe.
Possible topics:
Photosynthetic, but does not have light harvesting complex 2 (LHC2), which is commonly found in many photosynthetic bacteria.
References
Edited by student of Iris Keren
