Combined characterization of a new member of Marivita cryptomonadis strain LZ-15-2 isolated from cultivable phycosphere microbiota of highly toxic HAB dinoflagellate Alexandrium catenella LZT09

During our conveying the microbial structures of phycosphere microbiota (PM) derived from diverse marine harmful algal bloom (HAB) dinoflagellates, a new rod-sharped, white-colored cultivable bacterial strain, designated as LZ-15-2, was isolated from the PM of highly toxic Alexandrium catenella LZT09. Phylogenetic analysis of 16S rRNA gene sequence indicated that strain LZ-15-2 belonged to the genus Marivita within the family Rhodobacteraceae, and demonstrated the highest gene similarity of 99.2% to M. cryptomonadis CL-SK44^T, and less than 98.65% with other type strains of Marivita. Phylogenomic calculations on average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the new isolate and M. cryptomonadis CL-SK44^T were 99.86% and 99.88%, respectively. Genomic comparison of strain LZ-15-2 with available genomes of Marivita species further verified its taxonomic position within the genus of Marivita. Moreover, comparative genomics analysis showed a proximal similarity of strain LZ-15-2 with M. cryptomonadis CL-SK44^T, and it also revealed an open pan-genome status based on constructed gene accumulation curves among Marivita members with 9,361 and 1,712 genes for the pan- and core-genome analysis, respectively. Based on combined polyphasic taxonomic characteristics, strain LZ-15-2 represents a new member of M. cryptomonadis, and proposed as a potential candidate for further exploration of the detailed mechanisms governing the dynamic cross-kingdom algae-bacteria interactions (ABI) between PM and their algal host LZT09.