A novel bacterium designated G55GPT and pertaining to the family Acetobacteraceae was isolated from the gut of the Madagascar hissing cockroach Gromphadorhina portentosa. The Gram-negative cells were rod-shaped and non-motile. The complete 16S rRNA sequence of the strain G55GPT showed the highest pairwise similarity to Gluconacetobacter johannae CFN-Cf-55T (95.35 %), suggesting it represents a potential new genus of the family Acetobacteraceae. Phylogenetic analysis based on 16S rRNA gene and 106 orthologous housekeeping protein sequences revealed that G55GPT forms a monophyletic clade with the genus Commensalibacter, which thus far has also been isolated exclusively from insects. The G55GPT genome size was 2.70 Mbp, and the G+C content was 45.4 mol%, which is lower than most acetic acid bacteria (51-68 mol%) but comparable to Swingsia samuiensis AH83T (45.1 mol%) and higher than Commensalibacter intestini A911T (36.8 mol%). Overall genome relatedness indices based on gene and protein sequences strongly supported the assignment of G55GPT to a new genus within the family Acetobacteraceae. The percentage of conserved proteins, which is a useful metric for genus differentiation, was below 54 % when comparing G55GPT to type strains of acetic acid bacteria, thus strongly supporting our hypothesis that G55GPT is a member of a yet-undescribed genus. The fatty acid composition of G55GPT differed from that of closely related acetic acid bacteria, particularly given the presence of C19 : 1 ω9c/ω11c and the absence of C14 : 0 and C14 : 0 2-OH fatty acids. Strain G55GPT also differed in terms of metabolic features such as its ability to produce acid from d-mannitol, and its inability to produce acetic acid from ethanol or to oxidize glycerol to dihydroxyacetone. Based on the results of combined genomic, phenotypic and phylogenetic characterizations, isolate G55GPT (=LMG 31394T=DSM 111244T) is considered to represent a new species in a new genus, for which we propose the name Entomobacter blattae gen. nov., sp. nov.
Keywords: Acetobacteraceae; Entomobacter blattae; Gromphadorhina portentosa; cockroach microbiota.