Cultivation and characterization of the gut symbionts of honey bees and bumble bees: description of Snodgrassella alvi gen. nov., sp. nov., a member of the family Neisseriaceae of the Betaproteobacteria, and Gilliamella apicola gen. nov., sp. nov., a member of Orbaceae fam. nov., Orbales ord. nov., a sister taxon to the order 'Enterobacteriales' of the Gammaproteobacteria.

Gut-associated bacteria were isolated in axenic culture from the honey bee Apis mellifera and the bumble bees Bombus bimaculatus and B. vagans and are here placed in the novel genera and species Snodgrassella alvi gen. nov., sp. nov. and Gilliamella apicola gen. nov., sp. nov. Two strains from A. mellifera were characterized and are proposed as the type strains of Snodgrassella alvi (type strain wkB2(T) =NCIMB 14803(T) =ATCC BAA-2449(T) =NRRL B-59751(T)) and Gilliamella apicola (type strain wkB1(T) =NCIMB 14804(T) =ATCC BAA-2448(T)), representing, respectively, phylotypes referred to as 'Betaproteobacteria' and 'Gammaproteobacteria-1'/'Gamma-1' in earlier publications. These strains grew optimally under microaerophilic conditions, and did not grow readily under a normal atmosphere. The predominant fatty acids in both strains were palmitic acid (C16:0) and cis-vaccenic acid (C18:1ω7c and/or C18:1ω6c), and both strains had ubiquinone-8 as their major respiratory quinone. The DNA G+C contents were 41.3 and 33.6 mol% for wkB2(T) and wkB1(T), respectively. The Snodgrassella alvi strains from honey bees and bumble bees formed a novel clade within the family Neisseriaceae of the Betaproteobacteria, showing about 94% 16S rRNA gene sequence identity to their closest relatives, species of Stenoxybacter, Alysiella and Kingella. The Gilliamella apicola strains showed the highest 16S rRNA gene sequence identity to Orbus hercynius CN3(T) (93.9%) and several sequences from uncultured insect-associated bacteria. Phylogenetic reconstruction using conserved, single-copy amino acid sequences showed Gilliamella apicola as sister to the order 'Enterobacteriales' of the Gammaproteobacteria. Given its large sequence divergence from and basal position to the well-established order 'Enterobacteriales', we propose to place the clade encompassing Gilliamella apicola and O. hercynius in a new family and order, Orbaceae fam. nov. and Orbales ord. nov.