Taxonomic Comments

After réévaluation of the taxonomy of Ectothiorhodospiraceae on the basis of complete 16S rDNA sequences, the extremely halo-philic species were removed from Ectothiorhodospira and reassigned to the new genus Halorhodospira (Imhoff and SUling, 1996). Analyses of 16S rDNA sequences and fatty acid compositions supported the identification and species assignments of some strains, but demonstrated the misclassification of others (Imhoff and Süling, 1996; Thiemann and Imhoff, 1996). A number of strains have been tentatively assigned to E. mobilis. Strains 8112 (DSMZ 237), 8113 (DSMZ 238), and 8815 (DSMZ 240, Trtiper, 1970; Mandel et al., 1971) were confirmed as strains of E. mobilis. Strain 8115 (DSMZ 239, Triiper, 1970; Mandel et al.,

1971) was recognized as belonging to E. shaposhnikovii. Strains 51/7 (BN 9903, ATCC 51935) and C (BN 9902, Imhoff et al., 1978) were recognized as belonging to a new species, E. haloal-kaliphila. Strain BA 1010 (DSMZ 241, Matheron and Baulaigue,

1972) was found to represent the new species E. marina, and strain BA 1011 (Matheron and Baulaigue, 1972) was found to be most closely related to strain BA 1010. The recognition of strain DSMZ 239 as belonging to E. shaposhnikovii, the close relationship between E. shaposhnikovii and E. vacuolata, and that between E. mobilis and E. marismortui are supported by the DNADNA hybridization studies of Ivanova et al. (1985) and DNA restriction pattern analysis by Ventura et al. (1993). These results were substantiated by DNA-DNA reassociation studies by Ventura et al. (2000); these authors proposed the transfer of E. vacuolata to E. shaposhnikovii and E. marismortui to E. mobilis. Given the present state of knowledge, we do not follow this proposal here because of clearly distinctive phenotypic properties and ribotyp-ing patterns. In addition, strain BN 9903 (ATCC 51935) has been intensively studied and, though it is known from the literature as E. mobilis (Stackebrandt et al., 1984; Imhoff et al., 1982a; Imhoff, 1984a; Imhoff and Riedel, 1989; Imhoff and Thiemann, 1991; Imhoff et al., 1991; Zahr et al., 1992; Ventura et al., 1993), recent studies have led to the definition of this strain as the type strain of E. haloalkaliphila (Imhoff and Sûling, 1996).

the genus Ectothiorhodospira in Fig. BXII.y.19 of the chapter describing the family Ectothio-rhodospiraceae.

List of species of the genus Ectothiorhodospira

1. Ectothiorhodospira mobilis Pelsh 1936, 120AL emend. Ventura, Viti, Pastorelli and Giovannetti 2000, 589. mo'bi.lis. L. adj. mobilis mobile.

Cells vibrioid, curved in a short spiral or slightly bent rods, 0.7-1.0 X 2.0-2.6 |m (Fig. BXII.y.20). Motile by of 20% salts, either 180 g NaCl or 20 g Na2SO4 and 160 g NaCl are added to a final volume of 1 liter medium. The medium is dispensed into tightly closed screw-capped bottles that are completely filled and stored until use. Prior to inoculation, it is necessary to preincubate the bottles, after removal of an appropriate small volume, at the incubation temperature in order to achieve volume expansion.

The trace element solution SLA has the following composition: FeCl2-4H2O, 1.8 g; CoCl2-6H2O, 250 mg; NiCl2-6H2O, 10 mg; CuCl2-5H20,10 mg; MnCl2-4H2O, 70 mg; ZnCl2,100 mg; H3BO3, 500 mg; Na2MoO4-2H2O, 30 mg; and Na2SeO3-5H2O, 10 mg. These components are dissolved in 1 liter of doubly distilled water. The pH of the solution is adjusted with HCl to 2-3.

means of a polar tuft of flagella. Color of cell suspensions free of polysulfides and S0 is red. Absorption spectra of living cells show maxima at 378, 488, 516, 550, 590, 798, and 854 nm, with a shoulder at 892 nm. Photosynthetic pigments are bacteriochlorophyll a (esterified with phytol) and carotenoids of the spirilloxanthin series with spirillo-xanthin as the major component.

Obligately phototrophic and strictly anaerobic. Grow under anoxic conditions in the light with reduced sulfur compounds or organic carbon sources as electron donors. Pho-toautotrophic growth occurs with sulfide, thiosulfate, S0, sulfite and hydrogen. Acetate, pyruvate, malate, succinate, and fumarate used as organic carbon sources and electron donors. Some strains also use fructose, glucose, lactate, bu-tyrate, and propionate. Nitrogen sources are ammonia, glu-

TABLE BXII.c.9. Differential characteristics of Ectothiorhodospira species3
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