Taxonomic Comments

After reevaluation of the taxonomy of Ectothiorhodospiraceae based on complete 16S rDNA sequence comparison, the extremely halophilic species were removed from Ectothiorhodospira and reassigned to the new genus Halorhodospira (Imhoff and Suling, 1996).

Two different but closely related groups of H. halophila strains (12 strains included in the study) have been recognized based on fatty acid composition (Thiemann and Imhoff, 1996), 16S rDNA sequences (Imhoff and Suling, 1996), and DNA restriction pattern analysis (Ventura et al., 1993). This diversity is considered to be intraspecies variation, most likely related to different salt responses. The mol% G + C content of the DNA of H. halochloris is surprisingly low when compared to that of the two other species of this genus. Such a difference of nearly 20% within the same genus is unusual, particularly when given the rather similar sequences of the 16S rRNA gene. However, the mol% G + C values in Table BXII.y.9 of the chapter describing the family Ectothio-rhodospiraceae have been confirmed by two independent analyses of a total of three strains (personal communication of H. Hippe, Braunschweig).

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