based on published genomic data, in which he placed snodgrassella alvi as a sister species to stenoxybacter acetivorans, a species found in the intestines of termites, and placed it at the base of a taxon consisting of the genera neisseria (polyphyletic), eikenella, conchiformibius, alysiella, simonsiella, klingella, and bergeriella, along with the genus vitreoscilla. while the more basal taxa are found primarily in open habitats such as soil or aquatic environments, the derived forms including stenoxybacter and snodgrassella are generally attached to other organisms, primarily animals. a research group led by chinese researcher yong li grouped vitreoscilla, stenoxybacter, and snodgrassella into a taxon that additionally includes the species populibacter corticis, newly described in the paper, from the bark of a canadian poplar (populus × euramericana) canker as a sister species of snodgrassella alvi. strains and host specificity within the species, bacteria are classified according to strains taken from different hosts. accordingly, the strain wkb2 t used for the initial description was isolated from the gut of the western honeybee (apis mellifera) in connecticut. as a specialized gut symbiont, snodgrassella alvi evolved for millions of years with honeybees and bumblebees (genus bombus), where the bacteria are found. investigations revealed that the different strains of snodgrassella alvi from honey bees worldwide hardly differ in the gene sequences of the 16s rrna (in the v4 region) and are almost identical. in contrast, there are differences in the single-copy gene mind (an atpase that inhibits cell division) mainly in strains of snodgrassella alvi from honeybees, while bumblebees have only one strain of snodgrassella alvi. when comparing snodgrassella alvi strains from honey bees with those from different bumblebee species, it was found that genetic variability within individual honey bees of a hive is significantly higher than among bumblebees of a colony, the diversity being attributed to the establishment of a bee colony by swarms of workers as opposed to a single bumblebee. as a result, the gut of individual honeybees is usually colonized (86%) by multiple strains of snodgrassella alvi, whereas that of bumblebees usually contains only one strain (72%). in addition, host specificity of honey bee bacteria was found, with no strains found in both honey bee and bumblebee species. within bumblebees, there are some snodgrassella alvi strains that are species- or subgenus-specific, while others are found in multiple species of different subgenera. further analysis revealed that there are significantly greater differences in the protein-coding genes of honeybee strains of snodgrassella alvi, in contrast to those of rrna. this is explained by the fact that the variability of the 16s rrna loci had been restricted by frequent recombination within populations, while other regions of the genome continuously evolve and diversify in adaptation to changing ecological conditions in the gut.