Maricaulis alexandrii sp. nov., a novel active bioflocculants-bearing and dimorphic prosthecate bacterium isolated from marine phycosphere.

ABSTRACT

An aerobic, Gram-stain-negative, straight or curved rods and dimorphic prosthecate bacterium designated as strain LZ-16-1T was isolated from phycosphere microbiota of routinely laboratory-cultured and highly-toxic marine dinoflagellate Alexandrium catenella LZT09. Strain LZ-16-1T produces active bioflocculanting exopolysaccharides (EPS). Cells were dimorphic with non-motile prostheca, or non-stalked and motile by a single polar flagellum. Growth occurred at 10-40 °C, pH 5-9 and 1-8% (w/v) NaCl, with optimum growth at 25 °C, pH 7-8 in the presence of 2-4% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LZ-16-1T was affiliated to the genus Maricaulis, and closely related to M. parjimensis MCS 25T (99.5%) and M. virginensis VC-5T (99.0%). However, based on genome sequencing and phylogenomic calculations, the average nucleotide identity (ANI) and digtal DNA-DNA genome hybridization (dDDH) values between strains LZ-16-1T and its closest relative, M. parjimensis MCS 25T were only 85.0 and 20.9%, respectively. The dominant fatty acids of strain LZ-16-1T were summed feature 8, C160, C170, C180, C181 ω9c and summed feature 9. Major polar lipids were sulfoquinovosyl diacylglycerol, six glycolipids, one unidentified phospholipid and one unidentified polar lipid. The predominant isoprenoid quinone was Q-10. The DNA G + C content calculated from the genome was 63.6 mol%. Physiological and chemotaxonomic characterizations further confirmed the distinctiveness of strain LZ-16-1T from other Maricaulis members. Thus, strain LZ-16-1T represents a novel species of the genus Maricaulis, for which the name Maricaulis alexandrii sp. nov. (type strain LZ-16-1T = KCTC 72194T = CCTCC AB 2019006T) is proposed.