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

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 .

An aryl-homoserine lactone quorum-sensing signal produced by a dimorphic prosthecate bacterium

Many species ofProteobacteriaproduce acyl-homoserine lactone (AHL) compounds as quorum-sensing (QS) signals for cell density-dependent gene regulation. Most known AHL synthases, LuxI-type enzymes, produce fatty AHLs, and the fatty acid moiety is derived from an acyl-acyl carrier protein (ACP) intermediate in fatty acid biosynthesis. Recently, a class of LuxI homologs has been shown to use CoA-linked aromatic or amino acid substrates for AHL synthesis. By using an informatics approach, we found the CoA class of LuxI homologs exists primarily in α-Proteobacteria. The genome ofProsthecomicrobium hirschii, a dimorphic prosthecate bacterium, possesses aluxI-like AHL synthase gene that we predicted to encode a CoA-utilizing enzyme. We show theP. hirschiiLuxI homolog catalyzes synthesis of phenylacetyl-homoserine lactone (PA-HSL). Our experiments showP. hirschiiobtains phenylacetate from its environment and uses a CoA ligase to produce the phenylacetyl-CoA substrate for the LuxI homolog. By using an AHL degrading enzyme, we showed that PA-HSL controls aggregation, biofilm formation, and pigment production inP. hirschii. These findings advance a limited understanding of the CoA-dependent AHL synthases. We describe how to identify putative members of the class, we describe a signal synthesized by using an environmental aromatic acid, and we identify phenotypes controlled by the aryl-HSL.

Glycocaulis alkaliphilus sp. nov., a dimorphic prosthecate bacterium isolated from crude oil

A bacterial strain designated 6B-8T was isolated from crude oil from Daqing oilfield, China. Cells of strain 6B-8T were Gram-negative, aerobic, dimorphic and reproduced by means of binary fission. Strain 6B-8T could grow at 20–37 °C, pH 8–10 and 1–5 % (w/v) NaCl. Its genomic DNA G+C content was 62.0 mol%. The predominant cellular fatty acids were C18 : 1ω7c, C17 : 0, C18 : 0 and 11-methyl C18 : 1ω7c and the main hydroxy fatty acids were C12 : 0 3-OH and C12 : 1 3-OH when grown on marine agar 2216. The major quinone was Q-10 and the major polar lipids were three unidentified glycolipids. Phylogenetic analysis revealed that strain 6B-8T was a member of the family Hyphomonadaceae , sharing 99.6 and 99.4 % 16S rRNA gene sequence similarity with Glycocaulis abyssi LMG 27140T and Glycocaulis albus SLG210-30A1T, respectively, and less than 94.4 % similarity with the type strains of other members of the family Hyphomonadaceae . However, the DNA–DNA relatedness between strain 6B-8T and related strains G. abyssi LMG 27140T and G. albus SLG210-30A1T was 36±5 and 42±5 %, respectively. In addition, several phenotypic and genotypic features allowed differentiation of strain 6B-8T from G. abyssi LMG 27140T and G. albus SLG210-30A1T. Therefore, strain 6B-8T represents a novel species of genus Glycocaulis , for which the name Glycocaulis alkaliphilus sp. nov. is proposed. The type strain is 6B-8T ( = CGMCC 1.12428T = LMG 27410T).

Asticcacaulis solisilvae sp. nov., isolated from forest soil

An obligately aerobic, chemoheterotrophic, mesophilic prosthecate bacterium, designated strain CGM1-3ENT, was isolated from the enrichment cultures of forest soil from Cheonggyesan Mountain, Republic of Korea. Cells were Gram-reaction-negative, motile rods (1.3–2.4 µm long by 0.30–0.75 µm wide) with single flagella. The strain grew at 10–37 °C (optimum 25–30 °C) and at pH 4.5–9.5 (optimum 5.0–7.0). The major cellular fatty acids were C16 : 0, C18 : 1ω7c 11-methyl, C12 : 1 3-OH and summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c). The genomic DNA G+C content of strain CGM1-3ENT was 63.7 mol%. The closest phylogenetic neighbour to strain CGM1-3ENT was identified as Asticcacaulis biprosthecium DSM 4723T (97.2 % 16S rRNA gene sequence similarity) and the DNA–DNA hybridization value between strain CGM1-3ENT and A. biprosthecium DSM 4723T was less than 24.5 %. Strain CGM1-3ENT used d-glucose, d-fructose, sucrose, maltose, trehalose, d-mannose, d-mannitol, d-sorbitol, d-galactose, cellobiose, lactose, raffinose, fumarate, pyruvate, dl-alanine and glycerol as carbon sources. Based on data from the present polyphasic study, the forest soil isolate CGM1-3ENT is considered to represent a novel species of the genus Asticcacaulis , for which the name Asticcacaulis solisilvae sp. nov. is proposed. The type strain is CGM1-3ENT ( = AIM0088T = KCTC 32102T = JCM 18544T).

Brevundimonas abyssalis sp. nov., a dimorphic prosthecate bacterium isolated from deep-subsea floor sediment

A novel Gram-negative, aerobic, psychrotolerant, alkali-tolerant, heterotrophic and dimorphic prosthecate bacterium, designated strain TAR-001T, was isolated from deep-sea floor sediment in Japan. Cells of this strain had a dimorphic life cycle and developed an adhesive stalk at a site not coincident with the centre of the cell pole, and the other type of cell, a swarm cell, had a polar flagellum. Colonies were glossy, viscous and yellowish-white in colour. The temperature, pH and salt concentration range for growth were 2–41 °C, pH 6.5–10.0 and 1–4 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences confirmed that strain TAR-001T belongs to the family Caulobacteraceae of the class Alphaproteobacteria , and lies between the genus Brevundimonas and the genus Caulobacter . Levels of similarity between the 16S rRNA gene sequence of strain TAR-001T and those of the type strains of Brevundimonas species were 93.3–95.7 %; highest sequence similarity was with the type strain of Brevundimonas diminuta . Levels of sequence similarity between those of the type strains of Caulobacter species were 94.9–96.0 %; highest sequence similarity was with the type strain of Caulobacter mirabilis . The G+C content of strain TAR-001T was 67.6 mol%. Q-10 was the major respiratory isoprenoid quinone. The major fatty acids were C18 : 1ω7c and C16 : 0, and the presence of 1,2-di-O-acyl-3-O-[d-glucopyranosyl-(1→4)-α-d-glucopyranuronosyl]glycerol suggests strain TAR-001T is more closely to the genus Brevundimonas than to the genus Caulobacter . The mean DNA–DNA hybridization levels between strain TAR-001T and the type strains of two species of the genus Brevundimonas were higher than that of the genus Caulobacter . On the basis of polyphasic biological features and the 16S rRNA gene sequence comparison presented here, strain TAR-001T is considered to represent a novel species of the genus Brevundimonas , for which the name Brevundimonas abyssalis sp. nov. is proposed; the type strain is TAR-001T ( = JCM 18150T = CECT 8073T).

Marinicauda pacifica gen. nov., sp. nov., a prosthecate alphaproteobacterium of the family Hyphomonadaceae isolated from deep seawater

A marine prosthecate bacterium, designated strain P-1 km-3T, was isolated from deep seawater from the Pacific. Cells of strain P-1 km-3T were Gram-stain-negative, aerobic, catalase- and oxidase-positive, dimorphic rods with a single polar prostheca or flagellum. The strain hydrolysed gelatin and grew at 6–40 °C (optimum, 30 °C) and with 0.5–12 % (w/v) NaCl (optimum, 2 %). Phylogenetic analysis of the 16S rRNA gene sequences revealed that strain P-1 km-3T belonged to the family Hyphomonadaceae in the class Alphaproteobacteria and represented a separate lineage, located between the genera Oceanicaulis and Woodsholea . Sequence similarities of strain P-1 km-3T with type strains of species of the genera Oceanicaulis and Woodsholea were 93.2–93.9 %. The predominant cellular fatty acids in strain P-1 km-3T were C18 : 1ω7c, C18 : 0, 11-methyl C18 : 1ω7c, C17 : 0 and C19 : 0 cyclo ω8c. The major respiratory quinone of strain P-1 km-3T was Q-10. The polar lipids of strain P-1 km-3T comprised glucuronopyranosyldiglyceride (GUDG), monoglycosyldiglyceride (MGDG), sulfo-quinovosyl diacylglycerol (SQDG), phosphatidylglycerol (PG), an unidentified phospholipid (PL) and an unidentified lipid (L). The genomic DNA G+C content of strain P-1 km-3T was 66.0 mol%. On the basis of the polyphasic data presented in this study, strain P-1 km-3T is proposed to represent a novel species in a new genus, Marinicauda pacifica gen. nov., sp. nov., within the family Hyphomonadaceae . The type strain of the type species is P-1 km-3T ( = KACC 16526T = CGMCC 1.11031T).