Taxonomic studies were performed on some unknown Leuconostoc-like organisms from fermented Greek sausage. Comparative 16S rRNA sequence analysis showed the unidentified organisms represent a new line within the Leuconostoc paramesenteroides group of species. On the basis of the results of this and earlier phylogenetic investigations, it is proposed that Leuconostoc paramesenteroides and related species be reclassified in a new genus Weissella. In addition a new species, Weissella hellenica, is proposed for the isolates from fermented sausage.

The small‐subunit rRNA sequences of 51 species of Bacillus were determined by reverse transcription to elucidate the phylogenetic structure of the genus. Comparative analysis of the sequence data revealed five phylogenetically distinct clusters. Group 1 (Bacillus sensu stricto) included B. subtilis the type species of the genus and 27 other species. Group 2 consisted of B. sphaericus and five other bacilli and Sporosarcina ureae clustered within the confines of this group. Group 3 consisted of a phylogenetically coherent group of 10 species whereas groups 4 and 5 comprised two and three species respectively. It is evident that the genus Bacillus in genetically extremely heterogeneous and requires extensive taxonomic revision. The rRNA structures defined in the present study will provide a firm basis for the division of Bacillus into several phylogenetically distinct genera.

The phylogenetic status of members of the genus Lactococcus and some motile strains which react with Lancefield group N antiserum was examined by reverse transcriptase sequencing of 16S ribosomal ribonucleic acid. In agreement with earlier nucleic acid hybridization and immunological studies of superoxide dismutase the 16S sequence data clearly demonstrate that the lactococci represent a distinct phylogenetic group equivalent in rank to the genera Enterococcus and Streptococcus. The motile group N strains from chicken faeces and river water, however, were found to be phylogenetically unrelated to lactococci but displayed a closer, albeit loose, association with members of the genus Enterococcus. On the basis of the present sequence data and earlier chemotaxonomic studies it is proposed that the motile group N strains be classified in a new genus Vagococcus, as Vagococcus fluvialis sp. nov. The type strain of V. fluvialis is NCDO 2497.

SUMMARY The phylogenetic interrelationships of the genera Pediococcus and Aerococcus were investigated using reverse transcriptase sequencing of 16S rRNA. The genus Pediococcus was found to be phylogenetically heterogeneous. The four species P. acidilactici, P. damnosus, P. parvulus and P. pentosaceus formed a phylogenetically distinct group. Within this pediococcal cluster, P. acidilactici was closely related to P. pentosaceus whereas F. damnosus showed a specific relationship with P. parvulus. The species P. dextrinicus, although showing significant sequence relatedness with these pediococcal species, was peripheral to the genus. Pediococcus halophilus exhibited low sequence homology with all of the species examined and formed a distinct line of descent. Pediococcus halophilus exhibited a closer affinity with enterococci and carnobacteria than with the other lactic acid bacteria. Pediococcus urinae‐equi was phylogenetically very closely related to Aerococcus viridans. The 16S rRNA sequences of the type strains of these species differed by only two nucleotides (99.9% sequence homology) and clearly demonstrate that P. urinae‐equi is a member of the genus Aerococcus.

The phylogenetic interrelationships of members of the genus Carnobacterium and some atypical lactobacilli isolated from diseased salmonid fish were investigated by using reverse transcriptase sequencing of 16s rRNA. The four species Carnobacterium piscicola, Carnobacterium divergens, Carnobacterium gallinarum, and Carnobacterium mobile exhibited a high degree of sequence similarity with each other (ca. 96 to 98%) and formed a phylogenetically coherent group that was quite distinct from all other lactic acid bacteria. The sequence data clearly demonstrated that carnobacteria are phylogenetically closer to the genera Enterococcus and Vagococcus than to members of the genus Lactobacillus. The strains from fish were found to be phylogenetically related to the genus Vagococcus and represent a new species, Vagococcus salmoninarum. The type strain of Vagococcus salmoninarum is strain NCFB 2777.The genus Carnobacterium was proposed by Collins et al. (4) to accommodate the species Lactobacillus piscicola (17) and Lactobacillus divergens (18) and some so-called atypical lactobacilli isolated from poultry meat (24). Currently, four species, Carnobacterium piscicola (type species), Carnobacterium divergens, Carnobacterium gallinarum, and Carnobacterium mobile are recognized in this genus (4). Although these four species form a phenotypically coherent group (4, 9), the separateness of the genus Carnobacterium (in particular its relationship to the genus Lactobacillus) remains unclear. Members of the genus Carnobacterium differ from Lactobacillus species by their inability to grow on acetate medium (4, 9) and by their synthesis of oleic acid (c18:1A9,10) instead of cis-vaccenic acid (c18:1A11,12), which is produced by lactobacilli (4). At present these are the only criteria which distinguish the two genera.Sequencing of 16s rRNA by reverse transcriptase (20, 21) is currently the most rapid and powerful technique for elucidating the natural relationships of microorganisms (26). This method produces long stretches of sequence (ca. 95% of the total sequence), which enables precise phylogenetic relationships to be determined (26). In this study we determined 16s rRNA primary structures for members of the genus Carnobacterium by using reverse transcription in an attempt to clarify the relationship of these organisms to the genus Lactobacillus and other lactic acid bacteria. In addition, the phylogenetic position of two representative strains belonging to a group of atypical lactobacilli isolated from salmonid fish was also determined. MATERIALS AND METHODSCultures and cultivation. The test strains which we used are shown in Table 1. Strains of carnobacteria, enterococci, lactococci, leuconostocs, pediococci, and streptococci and fish isolates OS1-68T (T = type strain) and Rangen 128-81 were grown in YGPB broth (12) at 30°C. Strains OS1-68T and Rangen 128-81 were isolated by R.A. Holt, Oregon Department of Fish and Wildlife; strain OS1-68T was isolated in 1968 from an adult rainbow trout at the Oak Spring Hatchery * Corresponding...