> o aSymbols: +. positive in most strains; —. negative in most strains; ( + ). weak growth or microaerobic growth only; nd. not determined; Q-7. ubiquinone 7; Q-8. ubiquinone 8; Q-9. ubiquinone 9; Q-10. ubiquinone 10; Q-9/10. ubiquinones 9 and 10; MK-7. menaquinone 7; MK-9. menaquinone 9; MK-10. menaquinone 10; MK-9/10. 10. menaquinones 9 and 10.

'The first set of figures indicates the optimum salt concentration, and the second set- the ones in parentheses- indicates the range of salt concentrations tolerated.

List of species of the genus Rhodospirillum

1. Rhodospirillum rubrum (Esmarch 1887) Molisch 1907, 25al (Spirillum rubrum Esmarch 1887, 230.) rub'rum. M.L. neut. adj. rubrum red.

Cells are vibrioid shaped to spiral, 0.8-1.0 |im wide; one complete turn of a spiral is 1.5-2.5 |m wide and 7-10 |m long (Fig. BXII.a.1). Internal photosynthetic membranes

FIGURE BXII.a.1. Rhodospirillum rubrum ATCC 11170. Phase-contrast micrograph. Bar = 10 im. (Courtesy of N. Pfennig).

are of the vesicular type (Fig. BXII.a2). Anaerobic liquid cultures are pink to deep red, without a brownish tinge, under all conditions. Under oxic conditions, cells are colorless to light pink. Living cells show absorption maxima at 375-377, 510-517, 546-550, 590-595, 807-808, and 881885 nm. Photosynthetic pigments are bacteriochlorophyll a (esterified with geranylgeraniol as major and phytol as minor component) and carotenoids of the spirilloxanthin series with spirilloxanthin as the predominant component.

Cells preferentially grow photoheterotrophically under anoxic conditions in the light with various organic compounds as carbon and electron sources. Photoautotrophic growth occurs with H2 and sulfide as electron donors. Chemotrophic growth occurs under microoxic to oxic conditions in the dark. Fermentative metabolism with pyruvate under anoxic dark conditions and "oxidant-dependent" anaerobic dark metabolism are also possible. The carbon sources utilized are shown in Table BXII.a.2. In addition, alanine and asparagine are used and some strains use propanol. Ammonia, N2, several amino acids, and in some strains, nitrate, adenine, guanine, xanthin, and uric acid may be used as nitrogen source. Sulfate can serve as sole sulfur source. Small amounts of yeast extract may be favorable. Biotin is required as a growth factor.

Mesophilic freshwater bacterium with optimum growth at 30-35°C and pH 6.8-7.0 (pH range: 6.0-8.5). Habitat: stagnant and anoxic freshwater habitats that are exposed to the light. Major quinone components are Q-10 and RQ-10.

Type strain : ATCC 11170, DSM 467, NCIB 8255.

GenBank accession number (16S rRNA) : D30778, M32020.

2. Rhodospirillum photometricum Molisch 1907, 24AL' tri.cum. Gr. n. phos light; Gr. adj. metricus measuring; M.L. neut. adj. photometricum light measuring.

FIGURE BXII.a.2. Rhodospirillum rubrum strain FR1 grown anaerobically in the light. Note the vesicular structure of the intracytoplasmic membrane system. X 51,000. (Courtesy of G. Drews and R. Ladwig).

TABLE BXII.a.2. Carbon sources and electron donors used by species of the anoxygenic phototrophic bacteria belonging to the family


TABLE BXII.a.2. Carbon sources and electron donors used by species of the anoxygenic phototrophic bacteria belonging to the family


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