Rhodospirillum rubrum

Rhodospirillum rubrum (R. rubrum) is a Gram-negative, pink-coloured Proteobacterium, with a size of 800 to 1000 nanometers. It is a facultative anaerobe, thus capable of using oxygen for aerobic respiration under aerobic conditions, or an alternative terminal electron acceptor for anaerobic respiration under anaerobic conditions. Alternative terminal electron acceptors for R. rubrum include dimethyl sulfoxide or trimethylamine oxide. [2]

Rhodospirillum rubrum
Scientific classification
Kingdom:
Bacteria
Phylum:
Proteobacteria
Class:
Alphaproteobacteria
Order:
Rhodospirillales
Family:
Rhodospirillaceae
Genus:
Rhodospirillum
Species:
R. rubrum
Binomial name
Rhodospirillum rubrum
(Esmarch 1887) Molisch 1907[1]

Under aerobic growth photosynthesis is genetically suppressed and R. rubrum is then colorless. After the exhaustion of oxygen, R. rubrum immediately starts the production of photosynthesis apparatus including membrane proteins, bacteriochlorophylls and carotenoids, i.e. the bacterium becomes photosynthesis active. The repression mechanism for the photosynthesis is poorly understood. The photosynthesis of R. rubrum differs from that of plants as it possesses not chlorophyll a, but bacteriochlorophylls. While bacteriochlorophyll can absorb light up to a maximum wavelength of 800 to 925 nm, chlorophyll absorbs light having a maximum wavelength of 660 to 680 nm. R. rubrum is a spiral-shaped bacterium (spirillum, plural form: spirilla).

R. rubrum is also a nitrogen fixing bacterium, i.e., it can express and regulate nitrogenase, a protein complex that can catalyse the conversion of atmospheric dinitrogen into ammonia. When the bacteria are exposed to ammonia, darkness, and phenazine methosulfate, nitrogen fixation stops.[3] Due to this important property, R. rubrum has been the test subject of many different groups, so as to understand the complex regulatory schemes required for this reaction to occur.[4][5][6][7] It was in R. rubrum that, for the first time, post-translational regulation of nitrogenase was demonstrated. Nitrogenase is modified by an ADP-ribosylation in the arginine residue 101 (Arg101)[8] in response to the so-called "switch-off" effectors - glutamine or ammonia - and darkness.[9]

R. rubrum has several potential uses in biotechnology:

  • Quantitative accumulation of PHB (poly-hydroxy-butric-acid) precursors in the cell for the production of bioplastic.
  • Production of biological hydrogen fuel.
  • Model system for studying the conversion from light energy to chemical energy and regulatory pathways of the nitrogen fixation system.

References
  1. Parte, A.C. "Rhodospirillum". LPSN.
  2. Schultz JE, Weaver PF (January 1982). "Fermentation and Anaerobic Respiration by Rhodospirillum rubrum and Rhodopseudomonas capsulata". Journal of Bacteriology. 149 (1): 181–190. PMID 6798016.
  3. Kanemoto RH, Ludden PW (May 1984). "Effect of ammonia, darkness, and phenazine methosulfate on whole-cell nitrogenase activity and Fe protein modification in Rhodospirillum rubrum". Journal of Bacteriology. 158 (2): 713–20. PMC 215488. PMID 6427184.
  4. Teixeira PF, Jonsson A, Frank M, Wang H, Nordlund S (August 2008). "Interaction of the signal transduction protein GlnJ with the cellular targets AmtB1, GlnE and GlnD in Rhodospirillum rubrum: dependence on manganese, 2-oxoglutarate and the ADP/ATP ratio". Microbiology. 154 (Pt 8): 2336–47. doi:10.1099/mic.0.2008/017533-0. PMID 18667566.
  5. Selao TT, Nordlund S, Norén A (August 2008). "Comparative proteomic studies in Rhodospirillum rubrum grown under different nitrogen conditions". Journal of Proteome Research. 7 (8): 3267–75. doi:10.1021/pr700771u. PMID 18570453.
  6. Wolfe DM, Zhang Y, Roberts GP (October 2007). "Specificity and regulation of interaction between the PII and AmtB1 proteins in Rhodospirillum rubrum". Journal of Bacteriology. 189 (19): 6861–9. doi:10.1128/JB.00759-07. PMC 2045211. PMID 17644595.
  7. Jonsson A, Teixeira PF, Nordlund S (May 2007). "The activity of adenylyltransferase in Rhodospirillum rubrum is only affected by alpha-ketoglutarate and unmodified PII proteins, but not by glutamine, in vitro". The FEBS Journal. 274 (10): 2449–60. doi:10.1111/j.1742-4658.2007.05778.x. PMID 17419734.
  8. Pope MR, Murrell SA, Ludden PW (May 1985). "Covalent modification of the iron protein of nitrogenase from Rhodospirillum rubrum by adenosine diphosphoribosylation of a specific arginine residue". Proceedings of the National Academy of Sciences of the United States of America. 82 (10): 3173–7. Bibcode:1985PNAS...82.3173P. doi:10.1073/pnas.82.10.3173. JSTOR 25545. PMC 397737. PMID 3923473.
  9. Neilson AH, Nordlund S (November 1975). "Regulation of nitrogenase synthesis in intact cells of Rhodospirillum rubrum: inactivation of nitrogen fixation by ammonia, L-glutamine and L-asparagine". Journal of General Microbiology. 91 (1): 53–62. doi:10.1099/00221287-91-1-53. PMID 811763.
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