Maritimibacter alexandrii sp. nov., a New Member of Rhodobacteraceae Isolated from Marine Phycosphere

Marine phycosphere hosts cross-kingdom algae-bacteria interactions playing a variety of crucial roles in aquatic ecosystems especially for the prevention and control of harmful algal blooms (HABs). During the investigation of structural composition of phycosphere microbiota (PM) of diverse marine HAB dinoflagellates, a Gram-negative, strictly aerobic, non-motile and rod-shaped bacterium designated LZ-17 T was isolated from the phycosphere of highly toxic Alexandrium catenella LZT09. The 16S rRNA gene sequence analysis and the multilocus sequence analysis (MLSA) based on five protein-coding housekeeping genes ( atp D, gyr B, mut L, top A and rpo D) indicated that strain LZ-17 T was affiliated to the genus Maritimibacter within the family Rhodobacteraceae , and closely related to Maritimibacter alkaliphilus HTCC2654 T (99.1%), ‘ Maritimibacter harenae ’ DP07 T (97.9%) and M. lacisalsi X12M-4 T (95.7%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain LZ-17 T and the type strain of M. alkaliphilus were 96.9% and 74.7%. However, strain LZ-17 T could be clearly distinguished from its closest by the phenotypical and phenotypical characteristics. Strain LZ-17 T contained Q-10 as its major isoprenoid quinone, and summed feature 8 (C 18:1 ω 7c and/or C 18:1 ω 6c), C 16:0 and C 16:0 2-OH as the predominant fatty acids (>10%). The major polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylcholine. The DNA G + C content was 64.3 mol%. Based on the polyphasic taxonomic characterization, strain LZ-17 T represents a novel species of the genus Maritimibacter , for which the name Maritimibacter alexandrii sp. nov. is proposed, with the type strain LZ-17 T (=CCTCC 2019005 T = KCTC 72193 T ).