Tropicibacter alexandrii sp. nov., a novel marine bacterium isolated from the phycosphere of a dinoflagellate, Alexandrium minutum

摘要

An aerobic, Gram-negative, rod-shaped, non-motile bacterium was isolated from a liquid culture of the dinoflagellate Alexandrium minutum and designated as strain LMIT003(T). Analyses of 16S rRNA gene sequences revealed that this strain is affiliated with the genus Tropicibacter in the family Rhodobacteraceae of the class Alphaproteobacteria and shows high similarity (97.3%) with the type species Tropicibacter naphthalenivorans C02(T). Phylogenetic analysis based on core genes showed that the isolate groups with members of the genus Tropicibacter. The G + C content of strain LMIT003(T) was determined to be 61.9 mol%. The major fatty acids identified included summed feature 8 (C18:1 omega 7c/C18:1 omega 6c), C18:0, C12:1 3-OH and C16:0. The sole respiratory lipoquinone was found to be ubiquinone-10. The major polar lipids were found to be phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids and four unidentified phospholipids. The draft genome size of strain LMIT003(T) was determined to be 4.8 Mbp. The average nucleotide identity values between strain LMIT003(T) and reference Tropicibacter species were determined to be 78.7% (T. naphthalenivorans) and 74.2% (Tropicibacter phthalicicus). Based on physiological, chemotaxonomic and phylogenetic analysis, strain LMIT003(T) is concluded to represent a novel species in the genus Tropicibacter, for which the name Tropicibacter alexandrii sp. nov., is proposed. The type strain is LMIT003(T) (= CICC 24660(T) = KCTC 62895(T)).