Rhodospirillum rubrum
Encyclopedia
Rhodospirillum rubrum is a Gram-negative
, purple-coloured Proteobacterium
, with a size of 800 to 1000 nanometers.
It is a facultative anaerobe, it can therefore use alcoholic fermentation
under low oxygen conditions or use aerobic respiration
in aerobic conditions. 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 carotenoid
s, 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 a absorbs light having 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. 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 . 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) in response to the so-called "switch-off" effectors - glutamine
or ammonia
- and darkness.
R. rubrum has several potential uses in biotechnology
:
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
, purple-coloured Proteobacterium
Proteobacteria
The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....
, with a size of 800 to 1000 nanometers.
It is a facultative anaerobe, it can therefore use alcoholic fermentation
Ethanol fermentation
Ethanol fermentation, also referred to as alcoholic fermentation, is a biological process in which sugars such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products...
under low oxygen conditions or use aerobic respiration
Cellular respiration
Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...
in aerobic conditions. Under aerobic growth photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
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 carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
s, 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
Chlorophyll a
Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary...
, but bacteriochlorophylls. While bacteriochlorophyll a absorbs light having 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
Nitrogenase
Nitrogenases are enzymes used by some organisms to fix atmospheric nitrogen gas . It is the only known family of enzymes that accomplish this process. Dinitrogen is quite inert because of the strength of its N-N triple bond...
, a protein complex that can catalyse the conversion of atmospheric dinitrogen into ammonia. 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 . It was in R. rubrum that, for the first time, post-translational regulation
Post-translational regulation
Post-translational regulation refers to the control of the levels of active protein.There are several forms.It is performed either by means of reversible events or by means of irreversible events ....
of nitrogenase was demonstrated. Nitrogenase is modified by an ADP-ribosylation in the arginine
Arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
residue 101 (Arg101) in response to the so-called "switch-off" effectors - glutamine
Glutamine
Glutamine is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid but may become conditionally essential in certain situations, including intensive athletic training or certain gastrointestinal disorders...
or ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
- and darkness.
R. rubrum has several potential uses in biotechnology
Biotechnology
Biotechnology is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine and other fields requiring bioproducts. Biotechnology also utilizes these products for manufacturing purpose...
:
- Quantitative accumulation of PHB (poly-hydroxy-butric-acid) precursors in the cell for the production of biological plastic
- Production of biological hydrogen fuelHydrogen fuelAn ecologically-friendly fuel which uses electrochemical cells or combusts in internal engines to power vehicles and electric devices. It is also used in the propulsion of spacecraft and can potentially be mass produced and commercialized for passenger vehicles and aircraft.In a flame of pure...
- Model system for studying the conversion from light energy to chemical energyChemical energyChemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction or, to transform other chemical substances...
and regulatory pathways of the nitrogen fixationNitrogen fixationNitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
system.