Bombella favorum sp. nov. and Bombella mellum sp. nov., two novel species isolated from the honeycombs of Apis mellifera

As part of a study investigating the microbiome of bee hives and honey, two novel strains (TMW 2.1880^T and TMW 2.1889^T) of acetic acid bacteria were isolated and subsequently taxonomically characterized by a polyphasic approach, which revealed that they cannot be assigned to known species. The isolates are Gram-stain-negative, aerobic, pellicle-forming, catalase-positive and oxidase-negative. Cells of TMW 2.1880^T are non-motile, thin/short rods, and cells of TMW 2.1889^T are motile and occur as rods and long filaments. Morphological, physiological and phylogenetic analyses revealed a distinct lineage within the genus Bombella. Strain TMW 2.1880^T is most closely related to the type strain of Bombella intestini with a 16S rRNA gene sequence similarity of 99.5 %, and ANIb and in silico DDH values of 94.16 and 56.3 %, respectively. The genome of TMW 2.1880^T has a size of 1.98 Mb and a G+C content of 55.3 mol%. Strain TMW 2.1889^T is most closely related to the type strain of Bombella apis with a 16S rRNA gene sequence similarity of 99.5 %, and ANIb and in silico DDH values of 85.12 and 29.5 %, respectively. The genome of TMW 2.1889^T has a size of 2.07 Mb and a G+C content of 60.4 mol%. Ubiquinone analysis revealed that both strains contained Q-10 as the main respiratory quinone. Major fatty acids for both strains were C_{16 : 0}, C_{19 : 0} cyclo ω8c and summed feature 8, respectively, and additionally C_{14 : 0} 2-OH only for TMW 2.1880^T and C_{14 : 0} only for TMW 2.1889^T. Based on polyphasic evidence, the two isolates from honeycombs of Apis mellifera represent two novel species of the genus Bombella, for which the names Bombella favorum sp. nov and Bombella mellum sp. nov. are proposed. The designated respective type strains are TMW 2.1880^T (=LMG 31882^T=CECT 30114^T) and TMW 2.1889^T (=LMG 31883^T=CECT 30113^T).