Caulobacter profunda sp. nov., isolated from deep freshwater sediment

The Gram-stain-negative, aerobic, non-spore-forming, motile, with a single polar flagellum, or non-motile (stalked) and rod-shaped bacteria, DS48-5-2^T and DS48-6-3, were isolated from a sediment sample collected from a depth of 48 m taken from Daechung Reservoir, Republic of Korea. Comparative 16S rRNA gene sequence studies showed that the two isolates had clear affiliation with Alphaproteobacteria and the closest relatedness to Caulobacter mirabilis FWC 38^T, Caulobacter fusiformis ATCC 15257^T and Caulobacter daechungensis H-E3-2^T showing 98.5 %, 97.3 % and 97.3 % 16S rRNA gene sequence similarity, respectively, and 96.1-96.7 % similarity to all other species of the genus Caulobacter. The two isolates shared 100 % 16S rRNA gene sequence similarity. The predominant ubiquinone was Q-10. The major fatty acids were summed feature 8 (C₁₈: ₁ω6c and/or C_{18: 1}ω7c), C_{16: 0}, C_{18: 0}ω7c 11-methyl and summed feature 3 (C_{16: 1}ω6c and/or C_{16: 1}ω7c). The G+C contents of the genomic DNA of strains DS48-5-2^T and DS48-6-3 were 66.7 mol% and 66.2 mol%, respectively. DNA-DNA hybridization values of strains DS48-5-2^T and DS48-6-3 with C. mirabilis FWC 38^T, C. fusiformis ATCC 15257_T and C. daechungensis H-E3-2^T were 19.3 %-24.4 %. Thus, based on the evidence from polyphasic studies, it is proposed that strains DS48-5-2^T and DS48-6-3 are representatives of a novel species in the genus Caulobacter, for which the name Caulobacter profunda sp. nov. is proposed. The type strain is DS48-5-2^T (= KCTC 32480^T = JCM 19440^T).