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ABSTRACT The genus Brevundimonas consists of Gram-negative bacteria widely distributed in environment and can cause human infections. However, the genomic characteristics and pathogenicity of Brevundimonas remain poorly studied. Here, the whole-genome features of 24 Brevundimonas type strains were described. Brevundimonas spp. had relatively small genomes (3.13 ± 0.29 Mb) within the family Caulobacteraceae but high G+C contents (67.01 ± 2.19 mol%). Two-dimensional hierarchical clustering divided those genomes into 5 major clades, in which clades II and V contained nine and five species, respectively. Interestingly, phylogenetic analysis showed a one-to-one match between core and accessory genomes, which suggested coevolution of species within the genus Brevundimonas. The unique genes were annotated to biological functions like catalytic activity, signaling and cellular processes, multisubstance metabolism, etc. The majority of Brevundimonas spp. harbored virulence-associated genes icl, tufA, kdsA, htpB, and acpXL, which encoded isocitrate lyase, elongation factor, 2-dehydro-3-deoxyphosphooctonate aldolase, heat shock protein, and acyl carrier protein, respectively. In addition, genomic islands (GIs) and phages/prophages were identified within the Brevundimonas genus. Importantly, a novel Brevundimonas species was identified from the feces of a patient (suffering from diarrhea) by the analyses of biochemical characteristics, phylogenetic tree of 16S rRNA gene, multilocus sequence analysis (MLSA) sequences, and genomic data. The name Brevundimonas pishanensis sp. nov. was proposed, with type strain CHPC 1.3453 (= GDMCC 1.2503T = KCTC 82824T). Brevundimonas spp. also showed obvious slow growth compared with that of Escherichia coli. Our study reveals insights into genomic characteristics and potential virulence-associated genes of Brevundimonas spp., and provides a basis for further intensive study of the pathogenicity of Brevundimonas. IMPORTANCE Brevundimonas spp., a group of bacteria from the family Caulobacteraceae, is associated with nosocomial infections, deserve widespread attention. Our study elucidated genes potentially associated with the pathogenicity of the Brevundimonas genus. We also described some new characteristics of Brevundimonas spp., such as small chromosome size, high G+C content, and slow-growth phenotypes, which made the Brevundimonas genus a good model organism for in-depth studies of growth rate traits. Apart from the comparative analysis of the genomic features of the Brevundimonas genus, we also reported a novel Brevundimonas species, Brevundimonas pishanensis, from the feces of a patient with diarrhea. Our study promotes the understanding of the pathogenicity characteristics of Brevundimonas species bacteria.