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

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, C16:0, C17:0, C18:0, C18:1 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.

Sphingopyxis microcysteis sp. nov., a novel bioactive exopolysaccharides-bearing Sphingomonadaceae isolated from the Microcystis phycosphere.

During the study into the microbial biodiversity and bioactivity of the Microcystis phycosphere, a new yellow-pigmented, non-motile, rod-shaped bacterium containing polyhydroxybutyrate granules designated as strain Z10-6T was isolated from highly-toxic Microcystis aeruginosa Kützing M.TN-2. The new isolate produces active bioflocculating exopolysaccharides. Phylogenetic analysis based on 16S rRNA gene sequences indicated strain Z10-6T belongs to the genus Sphingopyxis with highest similarity to Sphingopyxis solisilvae R366T (98.86%), and the similarity to other Sphingopyxis members was less than 98.65%. However, both low values obtained by phylogenomic calculation of average nucleotide identity (ANI, 85.5%) and digital DNA-DNA hybridization (dDDH, 29.8%) separated the new species from its closest relative. The main polar lipids were sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified glycolipid and one unidentified aminophospholipid. The predominant fatty acids were summed feature 8, C17:1ω6c, summed feature 3, C16:0, C18:1ω7c 11-methyl and C14:0 2-OH. The respiratory quinone was ubiqunone-10, with spermidine as the major polyamine. The genomic DNA G + C content was 64.8 mol%. Several biosynthesis pathways encoding for potential new bacterial bioactive metabolites were found in the genome of strain Z10-6T. The polyphasic analyses clearly distinguished strain Z10-6T from its closest phylogenetic neighbors. Thus, it represents a novel species of the genus Sphingopyxis, for which the name Sphingopyxis microcysteis sp. nov. is proposed. The type strain is Z10-6T (= CCTCC AB2017276T = KCTC 62492T).