Genus I Ectothiorhodospira Pelsh 1936 120AL Johannes F Imhoff

Ec'to.thi'o.rho'do.spi'ra. Gr. prep. ectos outside; Gr. n. thios sulfur; Gr. n. rhodon the rose; Gr. n. spira the spiral; M.L. fem. n. Ectothiorhodospira spiral rose with sulfur outside.

Cells rod-shaped or vibrioid, also appearing as true spirals, 0.71.5 | m in diameter, motile by a polar tuft of flagella, multiply by binary fission, and may contain gas vesicles. Gram-negative and belong to the Gammaproteobacteria. Internal photosynthetic membranes are lamellar stacks that are continuous with the cy-toplasmic membrane. Photosynthetic pigments are bacterio-chlorophyll a and carotenoids.

Grow photoautotrophically under anoxic conditions with reduced sulfur compounds or hydrogen as electron donors, or photoheterotrophically with a limited number of organic compounds. Sulfide oxidized to sulfate, with S0, which is deposited outside the cells, as an intermediary product. Some species grow microaerobically to aerobically in the dark. Sodium chloride is required for growth, which is dependent on saline and alkaline conditions. Compatible solutes include glycine betaine, sucrose, and N-carbamoyl-L-glutamine amide. Growth factors are not required, but vitamin B12 enhances growth of some strains. Storage products are polysaccharides, poly-b-hydroxybutyrate, and polyphosphate.

Most species live in marine and saline environments that contain sulfide, have slightly to extremely alkaline pH, and are exposed to light, such as estuaries, salt flats, salt lakes, and soda lakes. Occasionally found in soil.

Type species: Ectothiorhodospira mobilis Pelsh 1936, 120.

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