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

We determined the 16S rRNA sequences of the type strains of species be longing to the genera Deleyn 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 subglaciesc ola. The members of the genera Deleya, Halomonas, and Halovibrio and t he misnamed organism Paracoccus halodenitrificans formed a monophyleti c 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 fre quency of occurrence of these signature features among other members o f the gamma subclass has remained stable during the expansion of the d atabase of rRNA sequences, The levels of 16S rRNA sequence similarity between members of the species belonging to the genera Deleya, Halomon as, and Halovibrio and the misnamed organism P. halodenitrificans rang ed from 91.5 to 100%; however, the level of sequence similarity for me mbers of well-resolved monophyletic subgroups which might represent se parate genera was 98%, At a sequence similarity level of 98% 10 subgro ups 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 Halovibri o should be placed in a single genus, the genus Halomonas, and we emen d the description of this genus, The resulting new combinations are Ha lomonas aquamarina (Deleya aquamarina Akagawa and Yamasato 1989), Halo monas variabilis (Halovibrio variabilis Fendrich 1988), Halomonas venu sta (Deleya venusta Baumann et al. 1983), Halomonas cupida (Deleya cup ida Baumann et al. 1983), Halomonas pacifica (Deleya pacifica Baumann et al, 1983), Halomonas marina (Deleya marina Baumann et al, 1983), Ha lomonas halophila (Deleya halophila Quesada et al, 1984), and Halomona s salina (Deleya salina Valderrama et al, 1991), We transfer the misna med organism P. halodenitrificans to the genus Halomonas as Halomonas halodenitrificans comb, nov, (P. halodenitrificans Robinson and Gibbon s 1952), The genus Zymobacter is closely related to the genus Halomona s. While the genus Zymobacter can be clearly distinguished from the ge nus Halomonas, these two taxa share important genotypic, chemotaxonomi c, and phenotypic characteristics. We propose that the genus Zymobacte r should be transferred to the family Halomonadaceae and emend the des cription of the family Halomonadaceae. The 168 rRNA sequence of Halomo nas subglaciescola ACAM 21 was significantly different from the 16S rR NA sequence of the type strain of Halomonas subglaciescola (strain ACA M 12) but was nearly identical to the 168 rRNA sequence of Halomonas h alodurans.