Abstract

Two Gram-stain-negative, aerobic, motile by means of flagella, short rod-shaped bacterial strains, designated IMCC43200(T) and IMCC45268(T), were isolated from coastal seawater samples collected from the South Sea of Korea. Strains IMCC43200(T) and IMCC45268(T) shared 98.6% 16S rRNA gene sequence similarity and were closely related to Congregibacter litoralis KT71(T) (98.8% and 98.7%, respectively). Complete whole-genome sequences of IMCC43200(T) and IMCC45268(T) were 3.93 and 3.86 Mb in size with DNA G + C contents of 54.8% and 54.2%, respectively. Average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains were 74.5% and 23.4%, respectively, revealing that they are independent species. The two strains showed ANI values of ≤ 75.8% and dDDH values of ≤ 23.0% to the type and only species of the genus Congregibacter (C. litoralis), indicating that each strain represents a novel species. Both strains contained summed feature 3 (comprising C(16:1) ω6c and/or C(16:1) ω7c) and summed feature 8 (comprising C(18:1) ω6c and/or C(18:1) ω7c) as major fatty acid constituents. The predominant isoprenoid quinone detected in both strains was ubiquinone-8 (Q-8). The major polar lipids of the two strains were phosphatidylethanolamine, phosphatidylglycerol, phospholipids, and aminolipids. Based on the phylogenetic, genomic, and phenotypic characterization, strains IMCC43200(T) and IMCC45268(T) were considered to represent two novel species within the genus Congregibacter, for which the names Congregibacter variabilis sp. nov. and Congregibacter brevis sp. nov. are proposed with IMCC43200(T) (= KCTC 8133(T) = NBRC 116295(T) = CCTCC AB 2023139(T)) and IMCC45268(T) (= KCTC 92921(T) = NBRC 116135(T)) as the type strains, respectively.

• Keywords: Congregibacter brevis;Congregibacter variabilis;New species;Polyphasic taxonomy;Seawater