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''Rhodospirillum rubrum'' (''R. rubrum'') is a Gram-negative, pink-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 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 an 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 (, among others). 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: * Quantitative accumulation of PHB (poly-hydroxy-butric-acid) precursors in the cell for the production of biological plastic * 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== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rhodospirillum rubrum」の詳細全文を読む スポンサード リンク
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