BALOs are present mainly in two classes: Alphaproteobacteria, which includes the genus Micavibrio, and Deltaproteobacteria, containing five families: Bdellovibrionaceae (including Bdellovibrio bacteriovorus HD100 and Bdellovibrio exovorus JSS), Peredibacteraceae (including Peredibacter starrii), Bacteriovoracaceae (including Bacterivores stolpii), Pseudobacteriovoracaceae (with the recent isolate Pseudobacteriovorax antillogorgiicola ), and Halobacteriovoraceae (including Halobacteriovorax marinus SJ and Halobacteriovorax litoralis JS5 ). The microbiota also contributes to the maintenance of the intestinal epithelium-barrier integrity by regulating enterocyte organisms (BALOs) and are now classified based on genomic and phenotypic criteria, as follows: (i) the 16S rRNA gene sequence, (ii) the β-subunit of the bacterial RNA polymerase (rpoB) gene sequence, (iii) the GC content (%), and (iv) the quantity of sodium chloride required for growth. These observations are consistent with the need to review and revise the taxonomy of these organisms. Thus, by 16S rDNA sequence analysis, the BALO appear to have multiple origins, contrary to the unified taxonomic grouping based on morphology and natural history. One freshwater isolate, James Island, was distinct from all other BALO (> 19%), but differed from Pseudomonas putida, a member of the gamma-Proteobacteria, by only 3%. However, both the Bdellovibrio and Bacteriovorax clades were closest to other representatives of the delta-Proteobacteria using maximum-likelihood. The difference between isolates in different clades is over 17%, a quantity similar to differences between bacterial species in different classes. This observation implies that the salt-water isolates arose from Bacteriovorax progenitors. The salt-water isolates form a subgroup (83% by bootstrap) and differ within the subgroup by less than 110%. The other group, supported 94% by bootstrap analysis, includes Bacteriovorax starrii, Bacteriovorax stolpii and the salt-water isolates. The genetic distance between these isolates was less than 12%. Each member of this group was isolated from either a freshwater or terrestrial source.

One group, supported 100% by bootstrap analysis, included all of the Bdellovibrio bacteriovorus isolates. When the 16S rDNA sequences were compared with representatives of other bacterial classes, 25 of the 26 BALO isolates clustered into two groups.

Primers that selectively amplify predator 16S rDNA, and not contaminating prey DNA, were utilized to study 17 freshwater and terrestrial and nine salt-water BALO isolates. The genetic diversity of these microbes was assessed by sequencing the 16S rRNA gene. Historically, these organisms have been classified together despite documented genetic differences between isolates. Bdellovibrio-and-like organisms (BALO) are Gram-negative, predatory bacteria that inhabit terrestrial, freshwater and salt-water environments.

16sr dna sequence analysis