The phylogeny of Aerococcus and Pediococcus as determined by 16S rRNA sequence analysis: description of Tetragenococcus gen. nov.

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 P. 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.