Altererythrobacter indicus sp. nov., isolated from wild rice (Porteresia coarctata Tateoka)

Altererythrobacter segetis sp. nov., Isolated from Farmland Soil

A Gram-stain-negative bacterium, designated YJ20^T, was isolated from rhizosphere soil of a spinach farmland at Shinan in Korea. Strain YJ20^T was found to be aerobic, non-motile rods which can grow at 10-33 °C (optimum, 28 °C), at pH 6.5-8.5 (optimum, pH 6.5-7.5) and in the absence of NaCl. The 16S rRNA gene sequence analysis showed that strain YJ20^T belongs to the genus Altererythrobacter with moderate sequence similarities to Altererythrobacter dongtanensis KCTC 22672^T (96.8%), Altererythrobacter soli MN-1^T (96.6%) and Altererythrobacter xinjiangensis S3-63^T (96.5%). The phylogenomic analysis based on the whole-genome sequence demonstrated that strain YJ20^T formed a distinct phyletic line with Altererythrobacter soli MN-1^T and Altererythrobacter salegens XY-R17^T showing average nucleotide identity (ANI) values of 79.4 and 77.5%, respectively. The predominant ubiquinone was identified as Q-10, and the major fatty acids were C_17:1 ω6c, C_18:1 ω7c and C_15:0 2-OH. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidycholin, sphingoglycolipid, an unidentified glycolipid, an unidentified phospholipid and an unidentified lipid. The G+C content of the genome was determined to be 66.3 mol%. On the basis of phenotypic, chemotaxonomic properties and phylogenetic and phylogenomic analyses in this study, strain YJ20^T is considered to represent a novel species in the genus Altererythrobacter, for which the name Altererythrobacter segetis sp. nov. is proposed. The type strain is YJ20^T (= KACC 19554^T = NBRC 113199^T).

Pseudopontixanthobacter vadosimaris gen. nov., sp. nov., isolated from shallow sea near Kueishan Island

A Gram-stain-negative and aerobic bacterial strain, designated as JL3514^T, was isolated from surface water of the hydrothermal system around Kueishan Island. The isolate formed red colonies and cells were non-flagellated, rod-shaped and contained methanol-soluble pigments. Growth was observed at 10-50 °C (optimum, 30 °C), at pH 5.0-9.0 (optimum, pH 7.0) and in the presence of 0-9 % (w/v) NaCl (optimum, 2 %). Strain JL3514^T was positive for catalase and weakly positive for oxidase. Results of 16S rRNA gene sequence analyses showed highest similarities to species in the family Erythrobacteraceae, namely Croceibacterium atlanticum (96.1 %), Pelagerythrobacter marensis (96.0 %), Tsuneonella rigui (96.0 %) and Altericroceibacterium xinjiangense (96.0 %). Phylogenetic analysis based on core gene sequences revealed that the isolate formed a distinct branch with the related species and it had a lower average amino acid identity value than the suggested threshold for genera boundaries. The major fatty acids (>5 %) were summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c), summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c), C_16 : 0, C_17 : 1  ω6c, C_14 : 0 2-OH and C_12 : 0. The dominant polar lipids comprised diphosphatidylglycerol, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, glycolipid, two unidentified lipids and one unidentified phospholipid. The main respiratory quinones were ubiquinone-10 (95.7 %) and ubiquinone-9 (4.3 %). The DNA G+C content from the genome was 63.0 mol%. Based on the presented data, we consider strain JL3514^T to represent a novel genus of the family Erythrobacteraceae, with the name Pseudopontixanthobacter vadosimaris gen. nov., sp. nov. The type strain is JL3514^T (=KCTC 62623^T=MCCC 1K03561^T).

Genomic-based taxonomic classification of the family Erythrobacteraceae

The family Erythrobacteraceae, belonging to the order Sphingomonadales, class Alphaproteobacteria, is globally distributed in various environments. Currently, this family consist of seven genera: Altererythrobacter, Croceibacterium, Croceicoccus, Erythrobacter, Erythromicrobium, Porphyrobacter and Qipengyuania. As more species are identified, the taxonomic status of the family Erythrobacteraceae should be revised at the genomic level because of its polyphyletic nature evident from 16S rRNA gene sequence analysis. Phylogenomic reconstruction based on 288 single-copy orthologous clusters led to the identification of three separate clades. Pairwise comparisons of average nucleotide identity, average amino acid identity (AAI), percentage of conserved protein and evolutionary distance indicated that AAI and evolutionary distance had the highest correlation. Thresholds for genera boundaries were proposed as 70 % and 0.4 for AAI and evolutionary distance, respectively. Based on the phylo-genomic and genomic similarity analysis, the three clades were classified into 16 genera, including 11 novel ones, for which the names Alteraurantiacibacter, Altericroceibacterium, Alteriqipengyuania, Alteripontixanthobacter, Aurantiacibacter, Paraurantiacibacter, Parerythrobacter, Parapontixanthobacter, Pelagerythrobacter, Tsuneonella and Pontixanthobacter are proposed. We reclassified all species of Erythromicrobium and Porphyrobacter as species of Erythrobacter. This study is the first genomic-based study of the family Erythrobacteraceae, and will contribute to further insights into the evolution of this family.

Structure-guided protein engineering increases enzymatic activities of the SGNH family esterases

BACKGROUND

Esterases and lipases hydrolyze short-chain esters and long-chain triglycerides, respectively, and therefore play essential roles in the synthesis and decomposition of ester bonds in the pharmaceutical and food industries. Many SGNH family esterases share high similarity in sequences. However, they have distinct enzymatic activities toward the same substrates. Due to a lack of structural information, the detailed catalytic mechanisms of these esterases remain barely investigated.

RESULTS

In this study, we identified two SGNH family esterases, CrmE10 and AlinE4, from marine bacteria with significantly different preferences for pH, temperature, metal ion, and organic solvent tolerance despite high sequence similarity. The crystal structures of these two esterases, including wild type and mutants, were determined to high resolutions ranging from 1.18 Å to 2.24 Å. Both CrmE10 and AlinE4 were composed of five β-strands and nine α-helices, which formed one compact N-terminal α/β globular domain and one extended C-terminal domain. The aspartic residues (D178 in CrmE10/D162 in AlinE4) destabilized the conformations of the catalytic triad (Ser-Asp-His) in both esterases, and the metal ion Cd²⁺ might reduce enzymatic activity by blocking proton transfer or substrate binding. CrmE10 and AlinE4 showed distinctly different electrostatic surface potentials, despite the similar atomic architectures and a similar swap catalytic mechanism. When five negatively charged residues (Asp or Glu) were mutated to residue Lys, CrmE10 obtained elevated alkaline adaptability and significantly increased the enzymatic activity from 0 to 20% at pH 10.5. Also, CrmE10 mutants exhibited dramatic change for enzymatic properties when compared with the wide-type enzyme.

CONCLUSIONS

These findings offer a perspective for understanding the catalytic mechanism of different esterases and might facilitate the industrial biocatalytic applications.

Altererythrobacter aquimixticola sp. nov., isolated from sediment sampled at the junction between the ocean and a freshwater spring

A Gram-stain-negative, aerobic, non-motile and coccoid-, ovoid- or rod-shaped bacterial strain, designated SSKS-13^T, was isolated from sediment sampled at the junction between the ocean and a freshwater spring at Jeju island, Republic of Korea. Strain SSKS-13^T grew optimally at 37 °C and in the presence of 2.0 % (w/v) NaCl. A neighbour-joining phylogenetic tree of 16S rRNA gene sequences showed that strain SSKS-13^T fell within the clade comprising the type strains of Altererythrobacter species, clustering with the type strains of Altererythrobacter lauratis, Altererythrobacter palmitatis and Altererythrobacter buctensis having 16S rRNA gene sequence similarities of 97.2-97.6 %. Strain SSKS-13^T exhibited 16S rRNA gene sequence similarities of less than 97.0 % to the type strains of the other recognized species. Strain SSKS-13^T contained Q-10 as the predominant ubiquinone and C18 : 1 ω7c as the major fatty acid. The major polar lipids detected in strain SSKS-13^T were phosphatidylethanolamine, phosphatidylglycerol and sphingoglycolipid. The DNA G+C content of strain SSKS-13^T was 64.6 mol%. The mean DNA-DNA relatedness values of strain SSKS-13^T with the type strains of A. lauratis, A. palmitatis and A. buctensis were 11.7-25.3 %. Differential phenotypic properties, together with the phylogenetic and genetic data, proved that strain SSKS-13^T is distinct from recognized Altererythrobacter species. On the basis of the data presented here, strain SSKS-13^T is considered to represent a novel species of the genus Altererythrobacter, for which the name Altererythrobacter aquimixticola sp. nov. is proposed. The type strain is SSKS-13^T (=KACC 19863^T=KCTC 62900^T=NBRC 113545^T).

Altererythrobacter amylolyticus sp. nov., isolated from lake sediment

An aerobic, motile, Gram-stain-negative bacterium, designated strain NS1T, was isolated from interfacial sediment from Taihu Lake, China. The strain formed yellow colonies on R2A medium. Cells were ovoid to rod-shaped and non-spore-forming. Growth occurred at 15–40 °C (optimum, 28 °C), at pH 5.0–10.5 (optimum, 6.5–7.5) and in the presence of 0–1 % (w/v) NaCl (optimum, 0 %). Phylogenetic trees based on 16S rRNA gene sequences showed that strain NS1T represented a member of the genus Altererythrobacter and had the highest sequence similarity to Altererythrobacter troitsensis CCTCC AB 2015180T (97.1 %). The average nucleotide identity value between strain NS1T and the closest related strain based on their genomes was 78.6 %. The predominant ubiquinone was Q-10. The major fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The polar lipids comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, an unidentified phospholipid, an unidentified glycolipid and six unidentified lipids. The genomic DNA G+C content was 66.6 mol%. On the basis of phenotypic and genotypic characteristics, strain NS1T represents a novel species of the genus Altererythrobacter , for which the name Altererythrobacter amylolyticus sp. nov. is proposed. The type strain is NS1T (=CGMCC 1.13679T=NBRC 113553T).

Altererythrobacter maritimus sp. nov., isolated from seawater

A rod-shaped, Gram-staining-negative and orange-pigmented bacterium, designated strain HME9302^T, was isolated from seawater of the Yellow Sea in the Republic of Korea. The phylogenetic tree based on 16S rRNA gene sequences showed that strain HME9302^T formed a lineage within the genus Altererythrobacter, and was most closely related to Altererythrobacter aurantiacus O30^T with 96.7 % sequence similarity. The major fatty acids were summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The major respiratory quinone was ubiquinone-10. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid and four unidentified lipids. The DNA G+C content was 60.8 mol%. On the basis of the evidence presented in this study, strain HME9302^T represents a novel species of the genus Altererythrobacter, for which the name Altererythrobacter maritimus sp. nov. is proposed with the type strain HME9302^T (=KCTC 32463^T=KACC 17617^T=CECT 8417^T).

Altererythrobacter insulae sp. nov., a lipolytic bacterium isolated from a tidal flat

A lipolytic, Gram-stain-negative, aerobic, non-motile and coccoid, ovoid or rod-shaped bacterial strain, designated BPTF-M16^T, was isolated from tidal flat sediment on the Yellow Sea in the Republic of Korea. Strain BPTF-M16^T grew optimally at 30 °C and in the presence of 2.0-3.0 % (w/v) NaCl. A phylogenetic tree of 16S rRNA gene sequences showed that strain BPTF-M16^T fell within the clade comprising the type strains of Altererythrobacter species. Strain BPTF-M16^T exhibited 16S rRNA gene sequence similarity values of 98.0 and 97.1 % to the type strains of Altererythrobacterishigakiensis and Altererythrobactermarinus, respectively, and of less than 97.0 % to the type strains of the other recognized species. Strain BPTF-M16^T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids detected in strain BPTF-M16^T were phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, sphingoglycolipid and one unidentified glycolipid. Mean DNA-DNA relatedness values of strain BPTF-M16^T with the type strains of A. ishigakiensis and A. marinus were 22 and 13 %, respectively. The average nucleotide identity value between strain BPTF-M16^T and the type strain of A. ishigakiensis was 76.80 %. Differential phenotypic properties, together with the phylogenetic and genetic data, revealed that strain BPTF-M16^T is separated from recognized Altererythrobacter species. On the basis of the data presented here, strain BPTF-M16^T is considered to represent a novel species of the genus Altererythrobacter, for which the name Altererythrobacter insulae sp. nov. is proposed. The type strain is BPTF-M16^T (=KCTC 62421^T=KACC 19609^T=NBRC 113190^T).

Altererythrobacter xixiisoli sp. nov., isolated from wetland soil

A Gram-stain-negative, coccoid, yellow, non-motile, aerobic bacterium, designated strain S36T, was isolated from soil of the Xixi wetland in Zhejiang province, PR China. Phylogenetic analysis, based on 16S rRNA gene sequences, revealed that strain S36T could represent a novel species of genus Altererythrobacter showing highest similarity to Altererythrobacter atlanticus 26DY36T (96.31 % 16S rRNA gene sequence similarity). The temperature, pH and NaCl concentration ranges for growth were 10-37 °C (optimum 32 °C), pH 5.0-10.0 (optimum pH 7.0) and 0.5-3 % (optimum 1 %, w/v), respectively. The predominant respiratory quinone of strain S36T was Q-10. The major fatty acids were C16 : 0, C17 : 1ω6c, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The G+C content of the genomic DNA was 62.7 mol%. These data all support the affiliation of strain S36T to the genus Altererythrobacter. The polar lipids profile of strain S36T comprised diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified phospholipids and two unidentified glycolipids. The results of physiological and biochemical tests allowed differentiation of strain S36T from other members of the genus Altererythrobacter. Therefore, strain S36T represents a novel species of the genus Altererythrobacter, for which the name Altererythrobacter xixiisoli sp. nov. is proposed; the type strain is S36T (=CGMCC 1.12804T=NBRC 110413T).

Altererythrobacter lauratis sp. nov. and Altererythrobacter palmitatis sp. nov., isolated from a Tibetan hot spring

Two Gram-negative, moderately thermophilic, yellow-pigmented, rod-shaped and motile bacterial strains, designated YIM 75003^T and YIM 75004^T, were isolated from sediment samples collected from the Tagejia hot spring in Tibet, western China. The taxonomic affiliation of the two strains was investigated by a polyphasic approach. Pairwise comparison of the 16S rRNA gene sequences showed that strains YIM 75003^T and YIM 75004^T are closely related to Altererythrobacter buctense M0322^T (97.2 and 97.1% respectively), while sharing 99.9% sequence similarity against each other. Optimum growth of the two strains was observed at 37-45 °C, pH 8.0 and in the presence of 1-6% NaCl (w/v). Their predominant respiratory quinone was found to be ubiquinone 10. The major fatty acids in both the strains were identified as summed feature 8 (C_18:1 ω6c and/or C_18:1 ω7c) and summed feature 4 (C_17:1 anteiso B and/or iso I). Their major polar lipid profiles were found to be diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol and sphingoglycolipid. The DNA G+C contents of strains YIM 75003^T and YIM 75004^T were determined to be 61.3 and 60.1 mol%, respectively. The DNA-DNA hybridization values between strains YIM 75003^T and YIM 75004^T, and between the two strains and their closely related phylogenetic neighbour A. buctense M0322^T (=CGMCC 1.12871^T) were less than 70%. Based on the morphological and physiological properties, phylogenetic analyses, chemotaxonomic characteristics and DNA-DNA relatedness values, the two strains can be distinguished from each other and from their phylogenetically closely related strain. Strains YIM 75003^T and YIM 75004^T are, therefore, considered to represent two novel species of the genus Altererythrobacter, for which the names Altererythrobacter lauratis sp. nov. (type strain YIM 75003^T = KCTC 52606^T = CCTCC AB2016268^T) and Altererythrobacter palmitatis sp. nov. (type strain YIM 75004^T = KCTC 52607^T = CCTCC AB2016270^T) are proposed.

Altererythrobacter soli sp. nov., isolated from desert sand

An alkaliphilic strain designed MN-1T was isolated from a desert sand sample collected from Tengger desert, north-western China. To delineate its taxonomic position, this Gram-stain-negative, rod-shaped, strictly aerobic bacterium was subjected to a polyphasic taxonomic study. Growth was observed at temperatures from 4 to 37 °C (optimum 30-32 °C), at salinities from 0 to 2 % (optimum 1 %) and at pH from 6.5 to 12.0 (optimum 7.0-9.0). Phylogenetic analysis based on 16S rRNA gene sequencing showed that strain MN-1T was a member of the genus Altererythrobacterbut could be distinguished from recognized species of this genus. Compared to the reference strains, the novel strain was flagellated and motile by means of polar flagella. The predominant respiratory quinone was ubiquinone-10 and the major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, phosphatidylglycerol, phosphatidylcholine, one unidentified glycolipid, one unidentified phospholipid and four unidentified lipids. The predominant fatty acids were C18 : 1ω7c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. These chemotaxonomic traits were in agreement with the characteristics of the genus Altererythrobacter. Strain MN-1T was most closely related to Altererythrobacter xinjiangensis S3-63T (96.9 % 16S rRNA gene sequence similarity), followed by Altererythrobacter dongtanensis JM27T (96.4 %) and Altererythrobacter marinus H32T (96.1 %). The G+C content of the genomic DNA of strain MN-1T was 67.0 mol%. On the basis of data from this polyphasic taxonomic study, strain MN-1T is proposed as the type strain of a novel species of the genus Altererythrobacter, named as Altererythrobacter soli sp. nov. (=KCTC 52135T=MCCC 1K02066T).

Description of Altererythrobacter aerius sp. nov., isolated from air, and emended description of the genus Altererythrobacter

A Gram-stain-negative, yellow-pigmented, ovoid to rod-shaped, strictly aerobic bacterial strain, designated 100921-2T, was isolated from air at the foot of Xiangshan Mountain. Phylogenetic and phenotypic analysis of the organism revealed that the isolate belongs to the genus Altererythrobacter. Strain 100921-2T showed high 16S rRNA gene sequence similarity (96.01-94.70 %) to other type strains of the genus Altererythrobacter, with the highest similarity to Altererythrobactermarensis MSW-14T. Growth of strain 100921-2T was observed at 4-50 °C (optimum, 30 °C), at pH 4.5-10.0 (optimum, pH 7.0) and at salinities of 0-10 % (w/v) NaCl (optimum 0-0.5 %). The major fatty acids were C18 : 1ω7c (27.8 %), C17 : 1ω6c (23.1 %), 11-methyl C18 : 1ω7c(11.9 %), summed feature 3 (9.1 %) and C15 : 0 2-OH (7.9 %). The predominant respiratory quinone was ubiquinone-10 (Q-10). Polar lipid analysis indicated the presence of diphosphatidylglycerol, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, two unknown phospholipids, five unknown polar lipids and two unknown glycolipids. The DNA G+C content of the type strain was 67.5 mol%. On the basis of the data from the polyphasic characterization, strain 100921-2T represents a novel species, for which the name Altererythrobacter aerius sp. nov. is proposed. The type strain is 100921-2T (=CFCC 14287T=KCTC 42844T).

Altererythrobacter rigui sp. nov., isolated from wetland freshwater

A non-motile and yellow-pigmented bacterium, designated strain WW3^T, was isolated from freshwater of Woopo wetland, Republic of Korea. Cells were Gram-reaction-negative, aerobic, catalase-positive and oxidase-negative. A maximum-likelihood phylogenetic tree based on 16S rRNA gene sequences showed that strain WW3^T forms an independent lineage within the genus Altererythrobacter. Strain WW3^T was related distantly to Altererythrobacter dongtanensisJM27^T and Altererythrobacter troitsensisKMM 6042^T (97.1% 16S rRNA gene sequence similarity). DNA-DNA relatedness between strain WW3^T and the reference strains was low (30-41 %). The major fatty acids of strain WW3^T were C17 : 1ω6c, C17 : 1ω8c, C15 : 0 2-OH and summed feature 8 comprising C18 : 1ω6c and/or C18 : 1ω7c. The predominant isoprenoid quinone of the isolate was ubiquinone-10. The DNA G+C content of strain WW3^T was 63 mol%. Phenotypic characteristics distinguished strain WW3^T from related species of the genus Altererythrobacter. On the basis of the evidence presented in this study,strain WW3^T represents a novel species of the genus Altererythrobacter, for which the name Altererythrobacter rigui sp. nov. is proposed. The type strain is WW3^T (=KCTC 42620^T =JCM 30975^T).

Altererythrobacter terrae sp. nov., isolated from mountain soil

A Gram-negative, non-motile, non-spore-forming, ovoid-shaped bacterium designated as SWU3(T) was isolated from mountain soil collected at Seoul Women's University, South Korea. Based on 16S rRNA sequence analysis, strain SWU3(T) was found to belong to the genus Altererythrobacter. It shares high sequence similarities with A. dongtanensis JM27(T) (96.6 %), A. epoxidivorans JCS350(T) (96.6 %), and A. troitsensis KMM 6042(T) (96.5 %). Growth was observed between 15 and 37 °C (optimum, 30 °C) with pH of 6-9 (optimum, pH 7.0). It could tolerate 0-2 % (w/v) NaCl. Its predominant quinone was found to be ubiquinone (Q-10). Its major cellular fatty acids were determined to be C17:1 ω6c, C18:1 ω7c, and summed featured 3 (C16:1 ω7c/C16:1 ω6c), all of which are similar characteristics to those of species within the genus Altererythrobacter. Its G + C molar content was found to be 58.4 mol%. Phylogenetic evidence, together with phenotypic characteristics showed that strain SWU3(T) represents a new species of the genus Altererythrobacter. The name Altererythrobacter terrae sp. nov. is proposed and the type strain is SWU3(T) (=KEMB 9004-128(T) = JCM 19177(T)).

Draft Genome Sequence of Altererythrobacter troitsensis JCM 17037, Isolated from the Sea Urchin Strongylocentrotus intermedius

The habitats of the genus Altererythrobacter are various, including marine sediment, seawater, rhizosphere of wild rice, desert sand, etc. The genome of the type strain of Altererythrobacter troitsensis JCM 17037, isolated from sea urchin, was sequenced. This study would not only facilitate the understanding of the physiology, adaptation, and evolution of the Altererythrobacter species, but also provide a good resource for the study of synthesis of astaxanthin, since several enzymes involved in the production of astaxanthin were predicted.

Altererythrobacter aestiaquae sp. nov., isolated from seawater

A Gram-stain-negative, coccoid- or oval-shaped, gliding bacterial strain, designated HDW-31T, belonging to the class Alphaproteobacteria , was isolated from seawater of the Yellow Sea, Korea, and was subjected to a taxonomic study using a polyphasic approach. Strain HDW-31T grew optimally at pH 7.0–8.0, at 30 °C and in the presence of 2–3 % (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences showed that strain HDW-31T fell within the clade comprising the genus Altererythrobacter , clustering with the type strains of Altererythrobacter luteolus and Altererythrobacter gangjinensis , with which strain HDW-31T exhibited 97.0 and 96.0 % sequence similarity values, respectively. Sequence similarities to the type strains of the other recognized species of the genus Altererythrobacter were 93.5–96.0 %. The DNA G+C content was 57.9 mol% and mean DNA–DNA relatedness between strain HDW-31T and the type strain of A. luteolus was 5.3 %. Strain HDW-31T contained Q-10 as the predominant ubiquinone and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and C16 : 0 as the major fatty acids. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, a sphingoglycolipid, two unidentified glycolipids and an unidentified lipid. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, demonstrated that strain HDW-31T is distinguishable from recognized species of the genus Altererythrobacter . On the basis of the data presented, strain HDW-31T is considered to represent a novel species of the genus Altererythrobacter , for which the name Altererythrobacter aestiaquae sp. nov. is proposed. The type strain is HDW-31T ( = KCTC 42006T = CECT 8527T).

Citrimicrobium luteum gen. nov., sp. nov., aerobic anoxygenic phototrophic bacterium isolated from the gut of a sea cucumber Stichopus japonicus

A Gram-stain negative, yellow-pigmented, motile, pleomorphic bacterium, designated strain CBA4602(T), was isolated from the gut of the sea cucumber Stichopus japonicus, which was collected from Jeju Island in the Republic of Korea. In a phylogenetic analysis based on the 16S rRNA gene, strain CBA4602(T) belonged to the order Sphingomonadales in the class Alphaproteobacteria. The 16S rRNA gene sequence similarity between strain CBA4602(T) and 'Citromicrobium bathyomarinum' JF-1, the most closely related strain having nonvalidly published name, was 98.4%, followed by 95.2-96.7% identities with sequence of the other closest strains in the genus Erythrobacter. Strain CBA4602(T) had bacteriochlorophyll a and carotenoids. Strain CBA4602(T) grew in 0-10% (w/v) NaCl, at 10-42°C and pH 6.0-8.0, with optimal growth in 1-2% NaCl, at 30-37°C and pH 7.0. Strain CBA4602(T) was positive for catalase and oxidase activities and was able to hydrolyse gelatine and Tween 20 and 40, but not starch, Tween 80 or L-tyrosine. The G+C content of genomic DNA from strain CBA4602(T) was 68.0 mol% and Q-10 was the major detected isoprenoid quinone. The polar lipids were three unidentified phospholipids, three unidentified glycolipids, and two unidentified lipids. The dominant fatty acids were anteiso-C15:0, C16:0, anteiso-C17:0 and C18:0. As considering the current taxonomic status of the genus 'Citromicrobium' and polyphasic taxonomic analyses, strain CBA4602(T) represents a novel genus and species. The name Citrimicrobium luteum is proposed for the type strain CBA4602(T) (=KACC 17668(T) =JCM 19530(T)).

Altererythrobacter xiamenensis sp. nov., an algicidal bacterium isolated from red tide seawater

A Gram-stain-negative, yellow-pigmented, aerobic bacterial strain, designated LY02T, was isolated from red tide seawater in Xiamen, Fujian Province, China. Growth was observed at temperatures from 4 to 44 °C, at salinities from 0 to 9 % and at pH from 6 to 10. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the isolate was a member of the genus Altererythrobacter , which belongs to the family Erythrobacteraceae . Strain LY02T was related most closely to Altererythrobacter marensis MSW-14T (97.2 % 16S rRNA gene sequence similarity), followed by Altererythrobacter ishigakiensis JPCCMB0017T (97.1 %), Altererythrobacter epoxidivorans JCS350T (97.1 %) and Altererythrobacter luteolus SW-109T (97.0 %). The dominant fatty acids were C18 : 1ω7c, C17 : 1ω6c and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c). DNA–DNA hybridization showed that strain LY02T possessed low DNA–DNA relatedness to A. marensis MSW-14T, A. ishigakiensis JPCCMB0017T, A. epoxidivorans JCS350T and A. luteolus SW-109T (mean±sd of 33.2±1.3, 32.1±1.0, 26.7±0.7 and 25.2±1.1 %, respectively). The G+C content of the chromosomal DNA was 61.2 mol%. The predominant respiratory quinone was ubiquinone-10 (Q-10). According to its morphology, physiology, fatty acid composition and 16S rRNA gene sequence data, the novel strain most appropriately belongs to the genus Altererythrobacter , but can readily be distinguished from recognized species. The name Altererythrobacter xiamenensis sp. nov. is proposed (type strain LY02T = CGMCC 1.12494T = KCTC 32398T = NBRC 109638T).

Altererythrobacter atlanticus sp. nov., isolated from deep-sea sediment

A Gram-stain-negative, short rod-shaped bacterium, designated 26DY36T, was isolated from a deep-sea sediment sample collected from the North Atlantic Rise. The isolate required NaCl and grew best with 2 % (w/v) sea salts at a temperature of 30–35 °C and at pH 7.0. It formed yellow colonies, produced carotenoid-like pigments and did not produce bacteriochlorophyll a. Strain 26DY36T was positive for hydrolysis of aesculin, gelatin, tyrosine and Tweens 20, 40, 60 and 80, but negative for hydrolysis of casein, DNA and starch. The major respiratory quinone was ubiquinone-10. The major polar lipid profile consisted of sphingoglycolipid, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and two unidentified glycolipids. The principal fatty acids (>5 %) were C18 : 1ω7c, C17 : 1ω6c, C15 : 0 2-OH and C16 : 0. The genomic DNA G+C content was 59.4 mol%. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain 26DY36T should be assigned to the genus Altererythrobacter . 16S rRNA gene sequence similarities between the isolate and the type strains of species of the genus Altererythrobacter were in the range 92.7–96.5 %. On the basis of phenotypic and genotypic data, strain 26DY36T represents a novel species of the genus Altererythrobacter , for which the name Altererythrobacter atlanticus sp. nov. (type strain, 26DY36T = CGMCC 1.12411T = JCM 18865T) is proposed.

Altererythrobacter gangjinensis sp. nov., a marine bacterium isolated from a tidal flat

A Gram-stain-negative, ochre-pigmented, strictly aerobic bacterium, designated strain KJ7T, was isolated from a tidal flat of the Gangjin bay in South Korea. Cells were halotolerant, non-motile, catalase- and oxidase-positive rods. Growth of strain KJ7T was observed at 5–35 °C (optimum, 25 °C), at pH 6.0–9.5 (optimum, pH 6.5–7.0) and in the presence of 0–9 % (w/v) NaCl (optimum, 2 %). The major cellular fatty acids were C18 : 1ω7c, C17 : 1ω6c, summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) and C16 : 0. The polar lipid pattern indicated the presence of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, a sphingoglycolipid, an unidentified phospholipid and two unidentified lipids. The G+C content of the genomic DNA was 60.2±0.9 mol% and the predominant respiratory quinone was Q-10. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain KJ7T formed a phyletic lineage distinct from other members of the genus Altererythrobacter and was most closely related to Altererythrobacter luteolus SW-109T and Altererythrobacter namhicola KYW48T (95.6 and 95.0 % 16S rRNA gene sequence similarity, respectively). On the basis of phenotypic, chemotaxonomic and molecular features, strain KJ7T represents a novel species of the genus Altererythrobacter , for which the name Altererythrobacter gangjinensis sp. nov. is proposed. The type strain is KJ7T ( = KACC 16190T = JCM 17802T).

Altererythrobacter troitsensis sp. nov., isolated from the sea urchin Strongylocentrotus intermedius

An aerobic, halotolerant, Gram-negative bacterium was isolated from the sea urchin Strongylocentrotus intermedius and subjected to taxonomic characterization. The strain, designated KMM 6042T, was rod-shaped, motile and yellow-pigmented. Phylogenetic analysis indicated that the strain was most closely related to the type strain of Altererythrobacter dongtanensis , and the level of 16S rRNA gene sequence similarity between the two was 99.0 %. However, the DNA–DNA relatedness between the two strains was 34.4±7.6 %. Physiological and chemotaxonomic properties clearly distinguished the novel strain from other species of the genus Altererythrobacter . It is thus evident from the phylogenetic and phenotypic analyses that strain KMM 6042T merits recognition as a novel species of the genus Altererythrobacter , for which the name Altererythrobacter troitsensis sp. nov. (type strain, KMM 6042T = KCTC 12303T = JCM 17037T) is proposed.

Altererythrobacter ishigakiensis sp. nov., an astaxanthin-producing bacterium isolated from a marine sediment

A Gram-negative, non-motile, non-spore-forming, halophilic rod, designated JPCCMB0017T, was isolated from a marine sediment of the coastal area of Okinawa, Japan. The isolate formed orange–red colonies on marine agar. Bacteriochlorophyll α was absent and sphingoglycolipid 1 and other carotenoids, including astaxanthin, adonixanthin and zeaxanthin, were present. Ubiquinone-10 (Q-10) was the main respiratory quinone and C18 : 1ω7c was the major cellular fatty acid. The G+C content of DNA was 59.1 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the isolate was a member of the genus Altererythrobacter in the family Erythrobacteraceae. Strain JPCCMB0017T exhibited 96.8 % 16S rRNA gene sequence similarity with Altererythrobacter marinus H32T. Unlike other members of the genus Altererythrobacter, strain JPCCMB0017T reduced nitrate. On the basis of genotypic and phenotypic data, a novel species is proposed to accommodate this isolate, with the name Altererythrobacter ishigakiensis sp. nov. The type strain is JPCCMB0017T ( = NITE-AP48T = ATCC BAA-2084T = NBRC 107699T).

Altererythrobacter xinjiangensis sp. nov., isolated from desert sand, and emended description of the genus Altererythrobacter

A Gram-negative, rod-shaped, non-motile, strictly aerobic bacterium, strain S3-63(T), was isolated from desert sand of Xinjiang, China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain S3-63(T) had highest similarity to type strains of the genus Altererythrobacter, i.e. Altererythrobacter marinus H32(T) (97.2% similarity), Altererythrobacter marensis MSW-14(T) (95.9%), Altererythrobacter aestuarii KCTC 22735(T) (95.5%), Altererythrobacter epoxidivorans JCS350(T) (95.1%), Altererythrobacter namhicola KCTC 22736(T) (95.1%), Altererythrobacter luteolus SW-109(T) (95.0%) and Altererythrobacter indicus LMG 23789(T) (93.5%). Growth occurred at 20-37 °C (optimum 30 °C), at pH 7.0-9.0 (optimum pH 8.0) and in 0-3% (w/v) NaCl (optimum 1%). The major respiratory quinone was ubiquinone-10 and the predominant cellular fatty acids were C(18:1)ω7c (50.8%), summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c; 12.6%), C(16:0) (12.3%), C(14:0) 2-OH (7.3%) and C(17:1)ω6c (4.5%). The DNA G+C content was 64.6 mol%. Therefore, the phylogenetic, physiological and chemotaxonomic data demonstrated that strain S3-63(T) represents a novel species of the genus Altererythrobacter, for which the name Altererythrobacter xinjiangensis sp. nov. is proposed; the type strain is S3-63(T) (=CCTCC AB 207166(T)=CIP 110125(T)). An emended description of the genus Altererythrobacter is provided.

Altererythrobacter dongtanensis sp. nov., isolated from a tidal flat

A Gram-negative, rod-shaped and non-spore-forming bacterial strain, JM27(T), was isolated from a tidal flat of Dongtan Wetland, Chongming Island, China. The strain formed smooth yellow colonies on R2A plates. Growth occurred at 10-37 °C (optimum, 30-37 °C), at pH 6.0-10.0 (optimum, pH 7.0-9.0) and in the presence of 0-1 % NaCl (optimum, 0 %). Catalase test was positive and oxidase test was negative. Ubiquinone 10 (Q10) was the major respiratory quinone. C₁₈:₀ω7c and C₁₇:₁ω6c were the most abundant fatty acids. Diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol were the major polar lipids. The DNA G+C content of strain JM27(T) was 66.4 mol%. The 16S rRNA gene sequence of the isolate showed highest similarity to that of Altererythrobacter marinus H32(T) (96.4 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain belonged to the genus Altererythrobacter of the family Erythrobacteraceae of the class Alphaproteobacteria. On the basis of phylogenetic analysis, whole-cell fatty acids, polar lipid compositions, and biochemical and physiological characteristics, strain JM27(T) is proposed to represent a novel species of the genus Altererythrobacter for which the name Altererythrobacter dongtanensis sp. nov. is proposed. The type strain is JM27(T) ( = KCTC 22672(T)  = CCTCC AB 209199(T)).

Altererythrobacter namhicola sp. nov. and Altererythrobacter aestuarii sp. nov., isolated from seawater

Two non-motile, orange- or yellow-pigmented bacteria, designated strains KYW48(T) and KYW147(T), were isolated from seawater collected from the South Sea, Republic of Korea. Cells of both strains were Gram-reaction-negative, aerobic and catalase- and oxidase-positive. The major fatty acids of strain KYW48(T) were C(18 : 1)ω7c (35.3 %), summed feature 3 (iso-C(15 : 0) 2-OH and/or C(16 : 1)ω7c) (22.7 %), C(17 : 1)ω6c (19.8 %), C(14 : 0) 2-OH (7.4 %) and C(16 : 0) (5.9 %), and those of strain KYW147(T) were C(18 : 1)ω7c (36.0 %), summed feature 3 (18.3 %), C(16 : 0) (14.7 %), 11-methyl C(18 : 1)ω7c (10.7 %), C(16 : 0) 2-OH (9.1 %) and C(18 : 1)ω9c (8.0 %). The predominant isoprenoid quinone of both strains was ubiquinone 10 (Q-10). The DNA G+C contents of strains KYW48(T) and KYW147(T) were 63.8 and 67.2 mol%, respectively. A phylogenetic tree based on 16S rRNA gene sequences showed that strains KYW48(T) and KYW147(T) were grouped with the members of the family Erythrobacteraceae and formed a distinct clade with the members of the genus Altererythrobacter (<95.7 % sequence similarity). On the basis of the evidence presented in this study, the novel species Altererythrobacter namhicola sp. nov. (type strain KYW48(T)  = KCTC 22736(T)  = JCM 16345(T)) and Altererythrobacter aestuarii sp. nov. (type strain KYW147(T)  = KCTC 22735(T)  = JCM 16339(T)) are proposed.

The potential of Cycloclasticus and Altererythrobacter strains for use in bioremediation of petroleum-aromatic-contaminated tropical marine environments

Cycloclasticus sp. A5, which has been suggested to be a major degrader of petroleum aromatics spilled in temperate seas, showed higher degrading activities for petroleum aromatics, at both 25 degrees C and tropical sea temperature 30 degrees C, than the novel aromatic-degrading isolates, related to Altererythrobacter epoxidivorans (97.5% similarity in the almost full-length 16S rRNA gene sequence) and Rhodovulum iodosum (96.3% similarity), obtained after enrichment on crude oil in a continuous supply of Indonesian seawater. Cycloclasticus A5 degraded petroleum aromatics at a similar rate or faster at 30 degrees C as compared to 25 degrees C, but its growth on acetate was severely inhibited at 30 degrees C. These results suggest that, although their abundance would be low in tropical seas not contaminated with aromatics, the Cycloclasticus strains could be major degraders of petroleum aromatics spilled in tropical seas. The 16S rRNA gene of the Cycloclasticus strains has been identified from Indonesian seawater, and the gene fragments showed 96.7-96.8% similarities to that of Cycloclasticus A5. Introducing Cycloclasticus A5 may be an ecologically advantageous bioremediation strategy for petroleum-aromatic-contaminated tropical seas because strain A5 would disappear at 30 degrees C after complete consumption of the aromatics. Altererythrobacter and Rhodovulum-related isolates grew well on pyruvate in 10% strength marine broth at 30 degrees C whereas Cycloclasticus A5 did not grow well on acetate in the broth at 30 degrees C. These growth results, along with its petroleum-aromatic-degrading activity, suggest that the Altererythrobacter isolate could be an important petroleum-aromatic degrader in and around nutrient-rich tropical marine environments.

Altererythrobacter marensis sp. nov., isolated from seawater

A novel Gram-negative bacterium, designated MSW-14(T), was isolated from seawater collected around Mara Island, Jeju, Republic of Korea. The organism was motile by means of a flagellum and showed optimum growth at 0-4 % NaCl, 30 degrees C and pH 7.1. Phylogenetic analyses based on 16S rRNA gene sequences showed that the isolate belonged to the family Erythrobacteraceae. The strain's closest phylogenetic neighbours were Altererythrobacter epoxidivorans JCS350(T) (97.7 % sequence similarity), Altererythrobacter luteolus SW-109(T) (97.3 %) and Altererythrobacter indicus MSSRF26(T) (95.0 %). The dominant cellular fatty acid was C(18 : 1) (summed feature 7, 52.8 %). The major ubiquinone was UQ-10. The DNA G+C content was 63.1 mol%. DNA-DNA hybridization values between strain MSW-14(T) and A. epoxidivorans KCCM 42314(T) and A. luteolus KCTC 12311(T) were 26.0-27.3 % and 9.8-15.2 %, respectively. On the basis of the data from the polyphasic characterization, strain MSW-14(T) represents a novel species, for which the name Altererythrobacter marensis sp. nov. is proposed. The type strain is MSW-14(T) (=KCTC 22370(T)=DSM 21428(T)).

Altererythrobacter marinus sp. nov., isolated from deep seawater

A taxonomic study was carried out on strain H32(T), which was isolated from a crude-oil-degrading consortium enriched from deep seawater of the Indian Ocean. The 16S rRNA gene sequence of strain H32(T) showed highest similarity to that of Altererythrobacter luteolus SW-109(T) (96.7 %); lower similarities were observed with other members of the genus Altererythrobacter (94.7-95.7 %) and with members of the genera Erythrobacter (94.5-96.3 %), Erythromicrobium (94.9 %) and Porphyrobacter (94.3-95.3 %). Phylogenetic analyses of all members of the family Erythrobacteraceae and several members of the family Sphingomonadaceae revealed that strain H32(T) formed a clade within the genus Altererythrobacter. The dominant fatty acids were C(16 : 0) (6.7 %), C(18 : 1)omega7c (44.3 %) and 11-methyl C(18 : 1)omega7c (25.4 %). The major respiratory quinone was ubiquinone 10. The DNA G+C content was 66.5 mol%. Strain H32(T) did not contain bacteriochlorophyll a. These characteristics are in good agreement with those of members of the genus Altererythrobacter. Therefore, according to its morphology, physiology, fatty acid composition and 16S rRNA gene sequence data, strain H32(T) belongs to the genus Altererythrobacter, but can be readily distinguished from known Altererythrobacter species. It is therefore proposed that strain H32(T) represents a novel species, Altererythrobacter marinus sp. nov., with H32(T) (=CCTCC AB 208229(T) =LMG 24629(T) =MCCC 1A01070(T)) as the type strain.