Unification of the Genera Deleya (Baumann et al. 1983), Halomonas (Vreeland et al. 1980), and Halovibrio (Fendrich 1988) and the Species Paracoccus halodenitrificans (Robinson and Gibbons 1952) into a Single Genus, Halomonas, and Placement of the Genus Zymobacter in the Family Halomonadaceae

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Abstract
We determined the 16S rRNA sequences of the type strains of species belonging to the genera Deleya and Halomonas for which no sequence data were available previously. We also determined the 16S rRNA sequence of ACAM 21, a representative strain of a biovar of Halomonas subglaciescola. The members of the genera Deleya, Halomonas, and Halovibrio and the misnamed organism Paracoccus halodenitrificans formed a monophyletic group within the gamma subclass of the Proteobacteria. The 16S rRNA sequences of the members of this group contained all of the signature features previously identified as characteristic of the group. The frequency of occurrence of these signature features among other members of the gamma subclass has remained stable during the expansion of the database of rRNA sequences. The levels of 16S rRNA sequence similarity between members of the species belonging to the genera Deleya, Halomonas, and the misnamed organism P. halodenitrificans ranged from 91.5 to 100%; however, the level of sequence similarity for members of well-resolved monophyletic subgroups which might represent separate genera was 98%. At a sequence similarity level of 98% 10 subgroups were resolved, but these groups could not be differentiated on the basis of chemotaxonomic or phenotypic characteristics. In this paper we propose that members of the genera Deleya, Halomonas, and Halovibrio should be placed in a single genus, the genus Halomonas, and we emend the description of this genus. The resulting new combinations are Halomonas aquamarina (Deleya aquamarina Akagawa and Yamasato 1989), Halomonas variabilis (Halovibrio variabilis Fendrich 1988), Halomonas venusta (Deleya venusta Baumann et al. 1983), Halomonas cupida (Deleya cupida Baumann et al. 1983), Halomonas pacifica (Deleya pacifica Baumann et al. 1983), Halomonas marina (Deleya marina Baumann et al. 1983), Halomonas halophila (Deleya halophila Quesada et al. 1984), and Halomonas salina (Deleya salina Valderrama et al. 1991). We transfer the misnamed organism P. halodenitrificans to the genus Halomonas as Halomonas halodenitrificans comb. nov. (P. halodenitrificans Robinson and Gibbons 1952). The genus Zymobacter is closely related to the genus Halomonas. While the genus Zymobacter can be clearly distinguished from the genus Halomonas, these two taxa share important genotypic, chemotaxonomic, and phenotypic characteristics. We propose that the genus Zymobacter should be transferred to the family Halomonadaceae and emend the description of the family Halomonadaceae. The 16S rRNA sequence of Halomonas subglaciescola ACAM 21 was significantly different from the 16S rRNA sequence of the type strain of Halomonas subglaciescola (strain ACAM 12) but was nearly identical to the 16S rRNA sequence of Halomonas halodurans.

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