A Gram-negative, rod-shaped, weakly motile, non-spore-forming bacterium (D9(T)) was isolated from the gut of Cylindroiulus fulviceps (Diplopoda) on 1/3-strength nutrient agar plates. On the basis of 16S rRNA gene sequence similarity, strain D9(T) was shown to be phylogenetically closely related to the type strain of Budvicia aquatica, the sole species of the genus Budvicia, family Enterobacteriaceae. The similarity of the 16S rRNA gene sequences of strain D9(T) and B. aquatica DSM 5075(T) was 98.4 %. Other strains that showed high pairwise similarities with the isolate belonged to the genus Yersinia: Y. frederiksenii ATCC 33641(T) (96.8 % 16S rRNA gene sequence similarity), Y. massiliensis CCUG 53443(T) (96.8 %), Y. pestis NCTC 5923(T) (96.8 %), Y. pseudotuberculosis ATCC 29833(T) (96.8 %), Y. similis CCUG 52882(T) (96.7 %) and Y. ruckeri ATCC 29473(T) (96.5 %). The similarities of sequences of the housekeeping genes rpoB, hsp60 and gyrB between strain D9(T) and B. aquatica DSM 5075(T) and other members of the Enterobacteriaceae were less than 94 %. Phylogenetic trees based on all four gene sequences unequivocally grouped the isolate with the type strain of B. aquatica and separately from the genus Yersinia. Cells contained the quinones Q-8, Q-7 and MK-8. The major polar lipids were phosphatidylglycerol and phosphatidylethanolamine. The G+C content of the DNA (48.3 mol%) and the whole-cell fatty acid composition of strain D9(T) (C(14 : 0), C(16 : 1)ω7c, C(16 : 0), cyclo-C(17 : 0) and C(18 : 1)ω7c as major components) were typical for members of the Enterobacteriaceae. DNA-DNA hybridization of strain D9(T) with B. aquatica DSM 5075(T) resulted in a relatedness of 30.4 %, indicating that the isolate did not belong to B. aquatica. Physiological tests allowed the phenotypic differentiation of strain D9(T) from B. aquatica DSM 5075(T) as well as from members of the genus Yersinia. From these results, it is concluded that strain D9(T) represents a novel species, for which the name Budvicia diplopodorum sp. nov. is proposed (type strain D9(T) =DSM 21983(T) = CCM 7845(T)). The description of the genus Budvicia is emended.