Maricaulis alexandrii sp. nov., a novel dimorphic prosthecate and active bioflocculants-bearing bacterium isolated from phycosphere microbiota of laboratory cultured highly-toxic Alexandrium catenella LZT09

Abstract An aerobic, Gram-stain-negative, straight or curved rods, prosthecate bacterium designated as LZ-16-1T was isolated from phycosphere microbiota of highly-toxic and laboratory cultured dinoflagellate Alexandrium catenella LZT09. This new isolate 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 and 2-4 % (w/v) NaCl, respectively. Phylogenetic analysis based on 16S rRNA indicated that strain LZ-16-1T was affiliated to the genus Maricaulis, and closely related to Maricaulis parjimensis MCS 25T (99.48%) and M. virginensis VC-5T (99.04%),. However, based on genome sequencing and phylogenomic calculations, the average nucleotide identity (ANI) and digtal DNA-DNA genome hybridization (dDDH) values between the two strains were only 85.0 and 20.9%, respectively. Strain LZ-16-1T owned Q-10 as predominant isoprenoid quinone; summed feature 8, C16:0, C17:0, C18:0, C18:1 ω9c and summed feature 9 as dominant fatty acids; and sulfoquinovosyl diacylglycerol, glycolipids and unidentified phospholipid as major polar lipids. The genomic DNA G+C content is 63.6 mol%. Physiological and chemotaxonomic characterization 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 .