Acinetobacter pengchengensis sp. nov., isolated from the urban wastewater of Shenzhen, Guangdong Province, China

Two bacterial strains, designated LH3_13ᵀ and NS4_7, were isolated from urban wastewater samples collected in Shenzhen, China. Cells were aerobic, Gram-stain-negative, oxidase-negative, catalase-positive, non-motile and short rods to coccobacilli. Phylogenetic analysis based on 16S rRNA gene sequences placed the two strains within the genus Acinetobacter , showing the highest sequence similarity to ‘Acinetobacter seohaensis’ SW-100 (98.44–98.39%). Among the validly published species, the closest relatives were Acinetobacter indicus and Acinetobacter baumannii , with sequence similarities of 97.5–97.4% and 96.5–96.3%, respectively, values below the generally accepted species demarcation threshold. Whole-genome sequencing and comparative genomic analyses further supported the novelty of the strains. The average nucleotide identity (ANI) values between strains LH3_13ᵀ and NS4_7 and their closest related species, Acinetobacter towneri DSM 14962ᵀ, were 92.5–92.6%, and the corresponding digital DNA–DNA hybridization (dDDH) values were 50.2–50.6%, both clearly below the species delineation thresholds. In contrast, ANI and dDDH values between LH3_13ᵀ and NS4_7 were 97.6 and 82.7%, respectively, indicating that they belong to the same species. Core-genome phylogenomic analysis based on 81 bacterial core genes confirmed that the 2 strains formed a distinct and well-supported clade within the genus Acinetobacter . Phenotypic, physiological and chemotaxonomic characteristics further differentiated strains LH3_13ᵀ and NS4_7 from their closest phylogenetic relatives. Based on the combined evidence from phylogenetic, genomic, phenotypic and chemotaxonomic analyses, strains LH3_13ᵀ and NS4_7 represent a novel species of the genus Acinetobacter, for which the name Acinetobacter pengchengensis sp. nov. is proposed. The type strain is LH3_13ᵀ (=JCM 37796ᵀ=GDMCC 1.4974ᵀ).