Effects of Hyphomonas Strains on the Growth of Red Algae Pyropia Species by Attaching Specifically to Their Rhizoids

Bacteria and marine macroalgae form close associations, while various bacteria affect the morphogenesis and growth of macroalgae. Hyphomonas strains exhibit normal morphogenetic activity in protoplasts of the red alga Pyropia yezoensis (nori). However, the effects of the bacteria on the growth of Pyropia from protoplast cells to regenerated thalli remain unknown. Here, we assessed the growth of P. yezoensis and Pyropia tenera using combined cultures of three Hyphomonas strains (LNM10-16, SCM-2, and LNM-9) and three algal media (artificial seawater with vitamins, artificial seawater, and natural seawater) over 7 weeks. Third week after culture, the three Hyphomonas strains showed almost similar levels of normal growth activity for both Pyropia species. However, at 7 weeks, significant differences were observed among the three Hyphomonas strains in terms of length, length-to-width ratio, and normal morphology of Pyropia thalli. LNM10-16 significantly promoted the thalli length and length-to-width ratios of both Pyropia species in artificial seawater without vitamins and natural seawater, compared with the other two Hyphomonas strains. P. yezoensis cultured in artificial seawater with vitamins showed a much higher demand for LNM10-16 in development of the thalli length than P. tenera. These results may be explained by differences in the growth activities of Hyphomonas strains and the nutrient requirements of Pyropia species. Furthermore, the bacteria were more specifically attached to the rhizoid surfaces of both species. This study is the first to reveal that Hyphomonas strains affect the growth of Pyropia species by attaching to their rhizoids.

Algicella marina gen. nov., sp. nov., a novel marine bacterium isolated from a Pacific red alga

A novel Gram-staining negative, strictly aerobic, rod-shaped, and non-motile bacterium, designated strain 9Alg 56^T, was isolated from the red alga Tichocarpus crinitus. The phylogenetic analysis based on 16S rRNA gene sequences placed the novel strain within the family Rhodobacteraceae, the order Rhodobacterales, the class Alphaproteobacteria, the phylum Pseudomonadota. The nearest neighbors of the new strain were Pontivivens insulae KCTC 42458^T, Oceanibium sediminis KCTC 62076^T, Halovulum dunhuangense YYQ-30^T and Monaibacterium marinum C7^T with 16S rRNA gene sequence similarity of 94.7, 94.4%, 93.1 and 92.7%, respectively. The AAI/ANI/dDDH values between 9Alg 56^T and the five species of the closest genera (Pontivivens, Oceanibium, Halovulum, Monaibacterium, and 'Oceanomicrobium') were 58.63-63.91%/ 75.91-77.37%/ 19.3-20.4%. The prevalent fatty acids of strain 9Alg 56^T were C_18:1 ω7c, C_18:0 and C_14:0 3-OH. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, phosphatidic acid, phosphatidylcholine, and two unidentified lipids. The DNA G+C content of strain 9Alg 56^T was 61.5 mol%. A combination of the genotypic and phenotypic data showed that the algal isolate represents a novel genus and species, for which the name Algicella marina gen. nov., sp. nov. is proposed. The type strain is 9Alg 56^T (= KCTC 72005^T = KMM 6775^T).

Sulfitobacter aestuariivivens sp. nov., isolated from a tidal flat

A Gram-stain-negative, aerobic, non-flagellated, coccoid, ovoid or rod-shaped bacterial strain, TSTF-M16^T, was isolated from a tidal flat on the Yellow Sea, Republic of Korea. The neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain TSTF-M16^T fell within a clade comprising the type strains of Sulfitobacter species. Strain TSTF-M16^T exhibited 16S rRNA gene sequence similarities of 98.5 and 98.1 % to the type strains of Sulfitobacter mediterraneus and Sulfitobacter sabulilitoris, respectively, and 96.2-97.8 % to the type strains of the other Sulfitobacter species. The average nucleotide identity and digital DNA-DNA hybridization values between the genomic sequences of strain TSTF-M16^T and the type strains of 16 Sulfitobacter species were 70.6-74.2 and 17.9-19.0 %, respectively. The DNA G+C content of strain TSTF-M16^T from genomic sequence data was 59.26 mol%. Strain TSTF-M16^T contained Q-10 as the predominant ubiquinone and C_18 : 1  ω7c as the major fatty acid. The major polar lipids of strain TSTF-M16^T were phosphatidylcholine, phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid. Distinguished phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain TSTF-M16^T is separated from recognized Sulfitobacter species. On the basis of the data presented here, strain TSTF-M16^T is considered to represent a novel species of the genus Sulfitobacter, for which the name Sulfitobacter aestuariivivens sp. nov. is proposed. The type strain is TSTF-M16^T (=KACC 21645^T=NBRC 114501^T).

Sulfitobacter alexandrii sp. nov., a new microalgae growth-promoting bacterium with exopolysaccharides bioflocculanting potential isolated from marine phycosphere

Marine phycosphere harbors unique cross-kingdom associations with enormous ecological significance in aquatic ecosystems as well as relevance for algal biotechnology industry. During our investigating the microbial composition and bioactivity of marine phycosphere microbiota (PM), a novel lightly yellowish and versatile bacterium designated strain AM1-D1^T was isolated from cultivable PM of marine dinoflagellate Alexandrium minutum amtk4 that produces high levels of paralytic shellfish poisoning toxins (PSTs). Strain AM1-D1^T demonstrates notable bioflocculanting bioactivity with bacterial exopolysaccharides (EPS), and microalgae growth-promoting (MGP) potential toward its algal host. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain AM1-D1^T was affiliated to the members of genus Sulfitobacter within the family Rhodobacteraceae, showing the highest sequence similarity of 97.9% with Sulfitobacter noctilucae NB-68^T, and below 97.8% with other type strains. The complete genome of strain AM1-D1^T consisted of a circular 3.84-Mb chromosome and five circular plasmids (185, 95, 15, 205 and 348 Kb, respectively) with the G+C content of 64.6%. Low values obtained by phylogenomic calculations on the average nucleotide identity (ANI, 77.2%), average amino acid identity (AAI, 74.7%) and digital DNA-DNA hybridization (dDDH, 18.6%) unequivocally separated strain AM1-D1^T from its closest relative. The main polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol, one unidentified phospholipid and one unidentified lipid. The predominant fatty acids (> 10%) were C_18:1 ω7c, C_19:0 cyclo ω8c and C_16:0. The respiratory quinone was Q-10. The genome of strain AM1-D1^T was predicted to encode series of gene clusters responsible for sulfur oxidation (sox) and utilization of dissolved organic sulfur exometabolites from marine dinoflagellates, taurine (tau) and dimethylsulfoniopropionate (DMSP) (dmd), as well as supplementary vitamin B₁₂ (cob), photosynthesis carotenoids (crt) which are pivotal components during algae-bacteria interactions. Based on the evidences by the polyphasic characterizations, strain AM1-D1^T represents a novel species of the genus Sulfitobacter, for which the name Sulfitobacter alexandrii sp. nov. is proposed. The type strain is AM1-D1^T (= CCTCC 2017277T = KCTC 62491^T).

Sulfitobacter algicola sp. nov., isolated from green algae

A novel Gram-stain-negative, aerobic, non-flagellated, non-motile, oval-rod-shaped and light pink to light tawny-pigmented bacterial strain (designated 1151^T) were isolated from marine green algae obtained from the coastal seawater of Weihai, China. Strain 1151^T was found to grow at 15-37 °C (optimum, 33 °C), pH 7.0-9.5 (optimum, 7.5-8.5) and in the presence of 1-6% (w/v) NaCl (optimum, 3%). Cells were oxidase-positive and catalase-positive. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 1151^T was a member of the genus Sulfitobacter and exhibited the hightest sequence similarity to Sulfitobacter indolifex DSM 14862^T (96.6%), followed by the sequence similarity to Sulfitobacter aestuarii hydD52^T (96.5%) and Sulfitobacter profundi SAORIC-263^T (96.5%). The average nucleotide identity and digital DDH values between strain 1151^T and Sulfitobacter indolifex DSM 14862^T were 69.9% and 20.9%, respectively. The average amino acid identity between strain 1151^T and Sulfitobacter pontiacus DSM 10014^T (type strain of the type species) was 62.3%. Q-10 was detected as the sole respiratory quinone. The dominant cellular fatty acids were sum feature 8 (C_{18: 1}ω7c; 44.1%), C_{20: 1}ω7c (29.7%) and C_{18: 0} (11.7%). The DNA G + C content of strain 1151^T was 51.8 mol%. The polar lipids included phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylcholine (PC), and three unidentified lipids (L1, L2 and L3). Based on the phylogenetic and phenotypic characteristics, strain 1151^T is considered to represent a novel species of the genus Sulfitobacter, for which the name Sulfitobacter algicola sp. nov. is proposed. The type strain is 1151^T (= KCTC 72513^T = MCCC 1H00384^T).

Arenibacterium halophilum gen. nov., sp. nov., a halotolerant bacterium in the family Rhodobacteraceae isolated from a coastal sand dune

A Gram-stain-negative, non-pigmented, non-spore-forming, motile, strictly aerobic bacterial strain, designated CAU 1492^T, was isolated from a coastal sand dune and its taxonomic position was examined using a polyphasic approach. Cells of strain CAU 1492^T grew optimally at 30 °C, pH 7.0 and in 3 % (w/v) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence of CAU 1492^T showed that it formed a distinct lineage within the family Rhodobacteraceae as a separate deep branch, with 96.8 % or lower sequence similarity values to representatives of the genera Marivita, Donghicola, Sulfitobacter, Marinovum, Phaeobacter, Primorskyibacter, Roseovarius and Aestuariihabitans. Strain CAU 1492^T was closely related to Marivita geojedonensis DPG-138^T (96.8 %), Donghicola eburneus SW-277^T (96.7 %), Sulfitobacter porphyrae SCM-1^T (96.7 %), Marinovum algicola FF3^T (96.6 %) and Aestuariihabitans beolgyonensis BB-MW15^T (96.4 %) based on 16S rRNA gene sequences. The major cellular fatty acids of strain CAU 1492^T were cyclo-C_19 : 0  ω8c and summed feature 8 (C_18 : 1  ω7c/C_18 : 1  ω6c). The polar lipid pattern was composed of phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid and an unidentified aminolipid. The strain contained Q-10 as the sole respiratory quinone. The draft genome of strain CAU 1492^T was 4.63 Mb with a DNA G+C content of 63.1 mol%. The genome includes 4292 protein-coding genes and a five rRNA operons. On the basis of the phenotypic, chemotaxonomic and genomic data, strain CAU 1492^T represents a novel genus in the family Rhodobacteraceae for which the name Arenibacterium halophilum gen. nov., sp. nov. is proposed. The type strain of Arenibacterium halophilum is CAU 1492^T (=KCTC 62998^T=NBRC 113696^T).

Description of Sulfitobacter sediminilitoris sp. nov., isolated from a tidal flat

A Gram-stain-negative bacterial strain, JBTF-M27T, was isolated from a tidal flat from Yellow Sea, Republic of Korea. Neighbor-joining phylogenetic tree of 16S rRNA gene sequences showed that strain JBTF-M27T fell within the clade comprising the type strains of Sulfitobacter species. Strain JBTF-M27T exhibited the highest 16S rRNA gene sequence similarity (98.8%) to the type strain of S. porphyrae. Genomic ANI and dDDH values of strain JBTF-M27T between the type strains of Sulfitobacter species were less than 76.1 and 19.2%, respectively. Mean DNA-DNA relatedness value between strain JBTF-M27T and the type strain of S. porphyrae was 21%. DNA G + C content of strain JBTF-M27T from genome sequence was 57.8% (genomic analysis). Strain JBTF-M27T contained Q-10 as the predominant ubiquinone and C18:1ω7c as the major fatty acid. The major polar lipids of strain JBTF-M27T were phosphatidylcholine, phosphatidylglycerol and one unidentified aminolipid. Distinguished phenotypic properties, along with the phylogenetic and genetic distinctiveness, revealed that strain JBTF-M27T is separated from recognized Sulfitobacter species. On the basis of the data presented, strain JBTF-M27T ( = KACC 21648T = NBRC 114356T) is considered to represent a novel species of the genus Sulfitobacter, for which the name Sulfitobacter sediminilitoris sp. nov. is proposed.

Antarcticimicrobium sediminis gen. nov., sp. nov., isolated from Antarctic intertidal sediment, transfer of Ruegeria lutea to Antarcticimicrobium gen. nov. as Antarcticimicrobium luteum comb. nov

A Gram-stain-negative, aerobic, non-flagellated and rod- or ovoid-shaped bacterium, designated as strain S4J41^T, was isolated from Antarctic intertidal sediment. The isolate grew at 0-37 °C and with 0.5-10 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed Tween 80 and gelatin. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain S4J41^T constituted a distinct phylogenetic line within the family Rhodobacteraceae and was closely related with some species in the genera Ruegeria, Phaeobacter, Pseudopuniceibacterium, Sulfitobacter, Puniceibacterium and Poseidonocella with 98.6-95.7 % 16S rRNA gene sequence similarities. The major cellular fatty acids were C_16 : 0, summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c) and C_18 : 0 and the major polar lipids were phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, phosphatidylethanolamine and one unidentified aminolipid. The sole respiratory quinone was Q-10. The genomic DNA G+C content of strain S4J41^T was 60.3 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data obtained in this study, strain S4J41^T is considered to represent a novel species in a new genus within the family Rhodobacteraceae, for which the name Antarcticimicrobium sediminis gen. nov., sp. nov. is proposed. The type strain is S4J41^T (=MCCC 1K03508^T=KCTC 62793^T). Moreover, the transfer of Ruegeria lutea Kim et al. 2019 to Antarcticimicrobium gen. nov. as Antarcticimicrobium luteum comb. nov. (type strain 318-1^T=JCM 30927^T=KCTC 72105^T) is also proposed.

Compositional Shifts of Bacterial Communities Associated With Pyropia yezoensis and Surrounding Seawater Co-occurring With Red Rot Disease

Pyropia yezoensis is commercially the most important edible red alga in China, and red rot disease is viewed as one of the major constraints for its cultivation. Microbes within the oomycetic genus Pythium have been reported as the causative agents for this disease; however, little is known about the interactions between the disease and the epiphytic and planktonic bacterial communities. In the present study, bacterial communities associated with uninfected, locally infected, and seriously infected thalli collected from cultivation farms, and within seawater adjacent to the thalli, were investigated using in-depth 16S ribosomal RNA (rRNA) gene sequencing in conjunction with assessing multiple environmental factors. For both thalli and seawater, uninfected and infected communities were significantly different though alpha diversity was similar. Phylogenetic differences between epiphytic bacterial communities associated with P. yezoensis were mainly reflected by the relative changes in the dominant operational taxonomic units (OTUs) assigned as genus Flavirhabdus, genus Sulfitobacter, and family Rhodobacteraceae. The prevalent OTUs in seawater also differed in relative abundance across the communities and were affiliated with diverse taxa, including the phyla Actinobacteria, Verrucomicrobia, and Bacteroidetes, and the classes Alpha- and Gamma-proteobacteria. The differentiation of bacterial communities associated with P. yezoensis and seawater was primarily shaped by reactive silicate (RS) content and salinity, respectively. In particular, 14 potential indicators (two OTUs on P. yezoensis and twelve OTUs in seawater) were identified that significantly differentiated P. yezoensis health statuses and correlated with environmental changes. Overall, the present study provides insights into the alterations of bacterial communities associated with P. yezoensis and surrounding seawater co-occurring with red rot disease. Observed changes were closely associated with health status of algal host, and highlight the potential of using community differentiation to forecast disease occurrence.

Sulfitobacter profundi sp. nov., isolated from deep seawater

A Gram-stain-negative, rod-shaped, obligately aerobic, chemoheterotrophic bacterium which is motile by means of a single polar flagellum, designated SAORIC-263^T, was isolated from deep seawater of the Pacific Ocean. Phylogenetic analyses based on 16S rRNA gene sequences and genomebased phylogeny revealed that strain SAORIC-263^T belonged to the genus Sulfitobacter and shared 96.1-99.9% 16S rRNA gene sequence similarities with Sulfitobacter species. Wholegenome sequencing of strain SAORIC-263^T revealed a genome size of 3.9Mbp and DNA G+C content of 61.3 mol%. The SAORIC-263^T genome shared an average nucleotide identity and digital DNA-DNA hybridization of 79.1-88.5% and 18.9-35.0%, respectively, with other Sulfitobacter genomes. The SAORIC-263^T genome contained the genes related to benzoate degradation, which are frequently found in deep-sea metagenome. The strain contained summed feature 8 (C_18:1ω7c), C_18:1ω7c 11-methyl, and C_16:0 as the predominant cellular fatty acids as well as ubiquinone-10 (Q-10) as the major respiratory quinone. The major polar lipids of the strain were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, and aminolipid. On the basis of taxonomic data obtained in this study, it is suggested that strain SAORIC-263^T represents a novel species of the genus Sulfitobacter, for which the name Sulfitobacter profundi sp. nov. is proposed. The type strain is SAORIC-263^T (= KACC 21183^T = NBRC 113428^T).

Sulfitobacter faviae sp. nov., isolated from the coral Faviaveroni

Three closely related, non-sporulating, aerobic, Gram-stain-negative, motile, rod-shaped isolates (S5-53T, S6-62 and S6-64) were obtained from mucus of corals Favia veroni from the Andaman Sea, India. Colonies grown on marine agar were small, circular and cream-coloured. Heterotrophic growth was observed at 10-40 °C and pH 6-10; optimum growth occurred at 25-30 °C and pH 7-8. 16S rRNA gene sequence analysis confirmed the isolates belonged to the genus Sulfitobacter and the three isolates shared more than 99 % pairwise sequence similarity. Strain S5-53T shared highest 16S rRNA gene sequence similarity of 98.43 % with Sulfitobacter dubius KMM 3554T. DNA-DNA relatedness among the three isolates was above 70 % whereas strain S5-53T showed less than 70 % relatedness with the type strains of closely related species. The DNA G+C content of strain S5-53T was 61 mol%. It contained phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and diphosphatidylglycerol as major polar lipids. Predominant fatty acids included C18 : 1ω7c, C18 : 1ω7c 11-methyl, C16 : 0 and C10 : 0 3-OH. Q10 was the major respiratory quinone. Based on this polyphasic analysis, the new isolates (S5-53T, S6-62 and S6-64) are considered to represent a novel species of the genus Sulfitobacter, for which the name Sulfitobacter faviae sp. nov. is proposed. The type strain is S5-53T(=JCM 31093T=LMG 29156T).

Paradonghicola geojensis gen. nov., sp. nov., isolated from seawater, Geoje-si, South Korea

A Gram-negative, non-motile, non-spore-forming and aerobic bacterium, designated FJ12(T), was isolated from seawater, Geoje-si, South Korea. Strain FJ12(T) was catalase and oxidase positive. Growth of strain FJ12(T) was optimally observed at 30 °C and pH 6 and grew in the presence of 0-11 % (w/v) NaCl (optimum 2-3 % NaCl). The phylogenic analysis based on 16S rRNA gene sequence of strains FJ12(T) showed the highest sequence similarity to those of Doghicola eburneus KCTC 12735(T) (95.4 %), Aestuariihabitans beolgyonensis KTCT 32324(T) (95.3 %), Sulfitobacter pontiacus KCTC 32185(T) (94.9 %), Roseisalinus antarcticus DSM 11466(T) (94.8 %) and Loktanella soesokkaensis KCTC 32425(T) (94.7 %). The major polar lipids of FJ12(T) were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, an unidentified aminolipid and unidentified lipids. It contained Q-10 as the predominant ubiquinone, and major fatty acid is C18:1 ω7c (51.7 %), C16:0 (24.0 %). The DNA G+C content of the strain FJ12(T) was 60 mol%. Based on physiological and chemotaxonomic characteristics, strain FJ12(T) should be regarded as the type species of a novel genus in the family Rhodobacteraceae for which the name Paradonghicola geojensis sp. nov. is proposed. The type strain FJ12(T) (=KEMB 3001-336(T)=JCM 30384(T)).

Pseudoseohaeicola caenipelagi gen. nov., sp. nov., isolated from a tidal flat

A Gram-stain-negative, non-motile, aerobic and pleomorphic bacterium, designated BS-W13T, was isolated from a tidal flat on the South Sea, South Korea, and its taxonomic position was investigated using a polyphasic approach. Strain BS-W13T grew optimally at 25 °C, at pH 7.0–8.0 and in the presence of 1.0–2.0 % (w/v) NaCl. Neighbour-joining and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences showed that strain BS-W13T clustered with the type strain of Seohaeicola saemankumensis , showing the highest sequence similarity (95.96 %) to this strain. Strain BS-W13T exhibited 16S rRNA gene sequence similarity values of 95.95, 95.91, 95.72 and 95.68 % to the type strains of Sulfitobacter donghicola , Sulfitobacter porphyrae , Sulfitobacter mediterraneus and Roseobacter litoralis , respectively. Strain BS-W13T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The polar lipid profile of strain BS-W13T, containing phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and one unidentified lipid as major components, was distinguishable from those of some phylogenetically related taxa. The DNA G+C content of strain BS-W13T was 58.1 mol%. The phylogenetic data and differential chemotaxonomic and other phenotypic properties revealed that strain BS-W13T constitutes a novel genus and species within family Rhodobacteraceae of the class Alphaproteobacteria , for which the name Pseudoseohaeicola caenipelagi gen. nov., sp. nov. is proposed. The type strain is BS-W13T ( = KCTC 42349T = CECT 8724T).

Sulfitobacter undariae sp. nov., isolated from a brown algae reservoir

A Gram-stain-negative, aerobic, non-spore-forming, non-flagellated and coccoid, ovoid or rod-shaped bacterial strain, W-BA2(T), was isolated from a brown algae reservoir in Wando of South Korea. Strain W-BA2(T) grew optimally at 25 °C, at pH 7.0-8.0 and in the presence of approximately 2.0-3.0% (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences revealed that strain W-BA2(T) fell within the clade comprising the type strains of species of the genus Sulfitobacter , clustering coherently with the type strains of Sulfitobacter donghicola and Sulfitobacter guttiformis showing sequence similarity values of 98.0-98.1%. Sequence similarities to the type strains of the other species of the genus Sulfitobacter were 96.0-97.4%. Strain W-BA2(T) contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids of strain W-BA2(T) were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain W-BA2(T) was 55.0 mol% and its DNA-DNA relatedness values with the type strains of Sulfitobacter donghicola , Sulfitobacter guttiformis and Sulfitobacter mediterraneus were 16-23%. The differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, revealed that strain W-BA2(T) is separated from other species of the genus Sulfitobacter . On the basis of the data presented, strain W-BA2(T) is considered to represent a novel species of the genus Sulfitobacter, for which the name Sulfitobacter undariae sp. nov. is proposed. The type strain is W-BA2(T) ( = KCTC 42200(T) = NBRC 110523(T)).

Sulfitobacter pseudonitzschiae sp. nov., isolated from the toxic marine diatom Pseudo-nitzschia multiseries

A taxonomic study was carried out on bacterial strain H3(T), which was isolated from the toxic marine diatom Pseudo-nitzschia multiseries. Cells of strain H3(T) were Gram-stain-negative, rod-shaped, non-motile and capable of reducing nitrate to nitrite, but not denitrification. Growth was observed at NaCl concentrations of 1-9%, pH 6-12 and 10-37 °C. It was unable to degrade aesculin or gelatin. The dominant fatty acids (>10 %) were C18:1ω7c/ω6c (summed feature 8) and C16:0. The respiratory ubiquinone was Q10. The major lipids were phosphatidylethanolamine, phosphatidylglycerol, an aminolipid and one unknown lipid, and the minor lipids were two phospholipids and three unknown lipids. The G+C content of the chromosomal DNA was 61.7 mol%. 16S rRNA gene sequence comparison showed that strain H3(T) was related most closely to Sulfitobacter donghicola DSW-25(T) (97.3% similarity) and levels of similarity with other species of the genus Sulfitobacter were 95.1-96.9%. The mean (± sd) DNA-DNA hybridization value between strain H3(T) and Sulfitobacter donghicola DSW-25(T) was 18.0 ± 2.25%. The average nucleotide identity between strain H3(T) and Sulfitobacter donghicola DSW-25(T) was 70.45%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain H3(T) formed a separate clade close to the genus Sulfitobacter and was distinguishable from phylogenetically related species by differences in several phenotypic properties. On the basis of the phenotypic and phylogenetic data, strain H3(T) represents a novel species of the genus Sulfitobacter, for which the name Sulfitobacter pseudonitzschiae is proposed (type strain H3(T) =DSM 26824(T) =MCCC 1A00686(T)).