Aurantiacibacter poecillastricola sp. nov., Isolated from the Marine Sponge, Poecillastra wondoensis, and Reclassification of Erythrobacter alti as Aurantiacibacter alti comb. nov

A Gram-stain-negative, facultative anaerobic rods, designated as strain 219JJ12-13T, was isolated from a marine sponge, Poecillastra wondoensis, in Jeju-do, Republic of Korea. The cells displayed catalase and oxidase activity and were non-motile. Strain 219JJ12-13T grew at 10-37°C (optimum, 25-30°C), pH 6.0-8.5 (optimum, pH 7.0-7.5), and in the presence of 0.5-6.0% (w/v) NaCl (optimum, 4.0-5.0%). The polar lipids comprised disphosphatidylglycerol, phosphatidylglycerol, phosphatidylcoline, phosphatidylethanolamine, sphingoglycolipid, two aminophosphoglycolipid, unidentified phospholipid, and two unidentified lipids. The isoprenoid quinone was identified as Q-10, and predominant cellular fatty acids were C17:1 ω6c, summed feature 3 (C16:1 ω7c/C16:1 ω6c), and summed feature 8 (C16:1 ω7c/C18:1 ω6c). The G+C content of the genomic DNA was 63.3%. The 16S rRNA gene and genome sequences-based phylogenetic analyses showed that strain 219JJ12-13T formed a distinct phyletic clade within the genus Aurantiacibacter. Genome relatedness values, including average nucleotide identity and digital DNA-DNA hybridization among strain 219JJ12-13T and closely related type strains, were 74.0-80.2% and 18.2-22.8%, respectively, both markedly below the thresholds for species delineation. Based on polyphasic taxonomic approach, strain 219JJ12-13T represents a novel species of the genus Aurantiacibacter, and the name Aurantiacibacter poecillastricola sp. nov. is proposed. The type strain is 219JJ12-13T (= KACC 23236T = LMG 33060T). The reclassification of Erythrobacter alti to the genus Aurantiacibacter as Aurantiacibacter alti comb. nov. is also proposed (= KCCM 90261T = NBRC 111903T).

Aurantiacibacter flavus sp. nov. and Aurantiacibacter gilvus sp. nov., isolated from the mudflat of Suaeda japonica colonies

Two novel strains were isolated from the mudflat of Suaeda japonica colonies in Incheon, Republic of Korea. Designated as DGU5T and DGU6T, these strains were Gram-stain-negative, facultatively anaerobic and rod-shaped and had yellowish colonies. Both strains were determined to belong to the genus Aurantiacibacter through phylogenetic analysis of their 16S rRNA sequences and draft genomes. The cells of strain DGU5T were non-motile and grew at temperatures ranging between 7-45°C (optimum, 25-30°C), pH 6.0-10.0 (optimum, 7.0-8.0) and in the presence of 0-11.0% NaCl (optimum, 2.0%). The cells of strain DGU6T were non-motile and grew in temperatures ranging from 10-45 °C (optimum, 30-35°C), pH 3.0-10.0 (optimum, 7.0-8.0) and in the presence of 0-11.0% NaCl (optimum, 2.0%). Overall genome relatedness index calculations revealed average nucleotide identity values (72.3-88.6%) and digital DNA-DNA hybridization values (18.8-35.9%) aligning with those of the genus Aurantiacibacter. The major fatty acids in both strains were C17:1 ω6c and summed feature 8 (C18:1 ω6c/C18:1 ω7c), while the predominant polar lipids were sphingoglycolipid, phosphatidylglycerol, and diphosphatidylglycerol. Phylogenetic, average nucleotide identity, digital DNA-DNA hybridization, physiological, and biochemical data collectively demonstrated the distinctiveness of the novel strains from other members within the family Erythrobacteraceae. We propose the names A. flavus sp. nov. (type strain DGU5T = KACC 23720T = TBRC 19015T) and A. gilvus sp. nov. (type strain DGU6T = KACC 23721T = TBRC 19016T) for the two strains.

Human milk microbial species are associated with infant head-circumference during early and late lactation in Guatemalan mother-infant dyads

Human milk contains abundant commensal bacteria that colonize and establish the infant's gut microbiome but the association between the milk microbiome and head circumference during infancy has not been explored. For this cross-sectional study, head-circumference-for-age-z-scores (HCAZ) of vaginally delivered breastfed infants were collected from 62 unrelated Mam-Mayan mothers living in eight remote rural communities in the Western Highlands of Guatemala during two stages of lactation, 'early' (6-46 days postpartum, n = 29) or 'late' (109-184 days postpartum, n = 33). At each stage of lactation, infants were divided into HCAZ ≥ -1 SD (early: n = 18; late: n = 14) and HCAZ < -1 SD (early: n = 11; late: n = 19). Milk microbiome communities were assessed using 16S ribosomal RNA gene sequencing and DESeq2 was used to compare the differential abundance (DA) of human milk microbiota with infant HCAZ subgroups at both stages of lactations. A total of 503 ESVs annotated 256 putative species across the 64 human milk samples. Alpha-diversity using Chao index uncovered a difference in microbial community richness between HCAZ ≥ -1 SD and HCAZ < -1 SD groups at late lactation (p = 0.045) but not at early lactation. In contrast, Canonical Analysis of Principal Coordinates identified significant differences between HCAZ ≥ -1 SD and HCAZ < -1 SD at both stages of lactation (p = 0.003); moreover, 26 milk microbial taxa differed in relative abundance (FDR < 0.05) between HCAZ ≥ -1 SD and HCAZ < -1 SD, with 13 differentially abundant at each lactation stage. Most species in the HCAZ ≥ -1 SD group were Streptococcus species from the Firmicutes phylum which are considered human colonizers associated with human milk whereas the HCAZ < -1 SD group at late lactation had more differentially abundant taxa associated with environmentally and 'potentially opportunistic' species belonging to the Actinobacteria genus. These findings suggest possible associations between brain growth of breastfed infants and the milk microbiome during lactation. Importantly, these data provide the first evidence of cross talk between the human milk microbiome and the infant brain that requires further investigation.

Aurantiacibacter sediminis sp. nov., a marine bacterium isolated from a tidal flat

A yellow-coloured bacterium, designated as strain JGD-13T, was isolated from a tidal flat in the Republic of Korea. Cells were Gram-stain-negative, aerobic, non-flagellated and rod-shaped. Growth was observed at 4–42 °C (optimum, 30 °C), at pH 6.0–12.0 (pH 7.0–8.0) and at 1–7 % (w/v) NaCl concentration (3 %). The 16S rRNA gene sequence analysis indicated that strain JGD-13T was closely related to Aurantiacibacter gangjinensis K7-2T with a sequence similarity of 98.2 %, followed by Aurantiacibacter aquimixticola JSSK-14T (98.1 %), Aurantiacibacter atlanticus s21-N3T (97.6 %), Aurantiacibacter zhengii V18T (97.6 %) and Aurantiacibacter luteus KA37T (97.5 %). The average nucleotide identity and digital DNA–DNA hybridization values with related strains were 70.3–76.2 % and 18.5–20.3 %. The genomic DNA G+C content was 60.2 mol%. Phylogenetic analysis using the maximum-likelihood method showed that strain JGD-13T formed a clade with A. aquimixticola JSSK-14T and A. gangjinensis K7-2T. The major fatty acids were summed feature 8 (39.7 %) and C17 : 1  ω6c (14.4 %). The predominant respiratory quinone was ubiquinone-10. The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, one sphingoglycolipid and three unidentified lipids. On the basis of phylogenetic, phenotypic and chemotaxonomic characteristics, strain JGD-13T represents a novel species within the genus Aurantiacibacter , for which the name Aurantiacibacter sediminis JGD-13Tsp. nov. is proposed. The type strain is JGD-13T (=KCTC 72892T=KACC 21676T=JCM 33995T).

Aurantiacibacter rhizosphaerae sp. nov., isolated from a rhizosphere mudflat of a halophyte and proposal to reclassify Erythrobacter suaedae Lee et al. 2019. and Erythrobacter flavus Yoon et al. 2003 as Aurantiacibacter suaedae comb. nov. and Qipengyuania flava comb. nov., respectively

A marine alphaproteobacterium, designated as strain GH3-10^T, was isolated from the rhizosphere mud of a halophyte (Suaeda japonica) collected at the seashore of Gangwha Island, Republic of Korea. The isolate was found to be Gram-stain-negative, strictly aerobic, catalase- and oxidase-positive, non-motile, short rods and produced orange-coloured colonies. The 16S rRNA gene- and whole genome-based phylogenetic analyses exhibited that strain GH3-10^T belonged to the genus Aurantiacibacter and was most closely related to Aurantiacibacter atlanticus s21-N3^T (98.7 % 16S rRNA gene sequence similarity) and Aurantiacibacter marinus KCTC 23554^T (98.4 %). The major respiratory quinone was ubiquinone-10. The polar lipids consisted of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, sphingoglycolipid and an unidentified lipid. The major fatty acids were C_18 : 1  ω7c, summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c) and C_18 : 1  ω7c 10-methyl. The DNA G+C content was 61.3 mol% (by genome). Average nucleotide identity and DNA-DNA relatedness values between the isolate and its phylogenetically closest relatives, together with phenotypic distinctness warranted the taxonomic description of a new species. On the basis of data obtained by a polyphasic approach, strain GH3-10^T (=KCTC 62379^T=JCM 32444^T) represents a novel species of the genus Aurantiacibacter, for which the name Aurantiacibacter rhizosphaerae sp. nov. is proposed. According to phylogenetic coherence based on 16S rRNA genes and core genomes, it is also proposed that Erythrobacter suaedae Lee et al. 2019. and Erythrobacter flavus Yoon et al. 2003 be transferred to Aurantiacibacter suaedae comb. nov. and Qipengyuania flava comb. nov., respectively.

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.

Description of Erythrobacter mangrovi sp. nov., an aerobic bacterium from rhizosphere soil of mangrove plant (Kandelia candel)

A novel Gram-stain negative, aerobic, non-motile, rod-shaped bacterium, designated as strain EB310^T, was isolated from rhizosphere soil of mangrove plant Kandelia candel in Fugong village, Zhangzhou, China. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain EB310^T belonged to the genus Erythrobacter, clustering with Erythrobacter pelagi JCM 17468^T, Erythrobacter lutimaris KCTC 42109^T and Erythrobacter marisflavi KCTC 62896^T, and showed the highest 16S rRNA gene sequence similarity of 97.5% to Erythrobacter pelagi JCM 17468^T. The genomic average nucleotide identity and in silico DNA-DNA hybridization values between strain EB310^T and the reference strains were 71.0-75.5% and 19.8-20.0%, respectively. Growth ranges of the isolate occurred at 10-45 °C (optimum 28-30 °C), pH 5.5-9.5 (optimum pH 7.5) and 0-9.0% NaCl concentrations (optimum 2.0%, w/v). The strain did not produce bacteriochlorophyll a and flexirubin, but produced carotenoids. The strain contained Q-10 as the predominant ubiquinone and summed feature 3 (C_16:1 ω7c/C_16:1 ω6c) and summed feature 8 (C_18:1 ω6c/C_18:1 ω7c) as the major fatty acids. The major polar lipids were sphingoglycolipid, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylcholine. Differential phenotypic characteristics, together with chemotaxonomic, phylogenetic and genomic distinctiveness, indicated that strain EB310^T is distinguishable from other members of the genus Erythrobacter. On the basis of the data exhibited, strain EB310^T is considered to represent a novel species of the genus Erythrobacter, for which the name Erythrobacter mangrovi sp. nov., is proposed. The type strain is EB310^T (= KCTC 72109^T = MCCC 1K03690^T). The genomic DNA G + C content is 62.9 mol%.

Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of Alphaproteobacteria

The class Alphaproteobacteria is comprised of a diverse assemblage of Gram-negative bacteria that includes organisms of varying morphologies, physiologies and habitat preferences many of which are of clinical and ecological importance. Alphaproteobacteria classification has proved to be difficult, not least when taxonomic decisions rested heavily on a limited number of phenotypic features and interpretation of poorly resolved 16S rRNA gene trees. Despite progress in recent years regarding the classification of bacteria assigned to the class, there remains a need to further clarify taxonomic relationships. Here, draft genome sequences of a collection of genomes of more than 1000 Alphaproteobacteria and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa recognized as problematic long ago but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera and of a variety of genera to other families. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which are confirmed as valuable taxonomic markers. Similarly, analysis of the gene content was shown to provide valuable taxonomic insights in the class. Significant incongruities between 16S rRNA gene and whole genome trees were not found in the class. The incongruities that became obvious when comparing the results of the present study with existing classifications appeared to be caused mainly by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. Another probable cause of misclassifications in the past is the partially low overall fit of phenotypic characters to the sequence-based tree. Even though a significant degree of phylogenetic conservation was detected in all characters investigated, the overall fit to the tree varied considerably.

Sulfur-Containing Carotenoids from A Marine Coral Symbiont Erythrobacter flavus Strain KJ5

Erythrobacter flavus strain KJ5 (formerly called Erythrobacter sp. strain KJ5) is a yellowish marine bacterium that was isolated from a hard coral Acropora nasuta in the Karimunjawa Islands, Indonesia. The complete genome sequence of the bacterium has been reported recently. In this study, we examined the carotenoid composition of this bacterium using high-performance liquid chromatography coupled with ESI-MS/MS. We found that the bacterium produced sulfur-containing carotenoids, i.e., caloxanthin sulfate and nostoxanthin sulfate, as the most abundant carotenoids. A new carotenoid zeaxanthin sulfate was detected based on its ESI-MS/MS spectrum. The unique presence of sulfated carotenoids found among the currently known species of the Erythrobacter genus were discussed.

Erythrobacter spongiae sp. nov., isolated from marine sponge

A taxonomic study was carried out on strain HN-E23T, which was isolated from sponge collected from Yangpu Bay, Hainan, China. Cells of strain HN-E23T were Gram-stain-negative, non-motile, orange-yellow-pigmented, short rods, that could grow at 10–40 °C (optimum, 28 °C), at pH 5–11 (optimun, pH 7) and in 0.5–12 % (w/v) NaCl (optimum, 3 %). This isolate was positive for oxidase, catalase, and the hydrolysis of aesculin, but negative for indole production and the reduction of nitrate. The phylogenetic tree based on 16S rRNA gene sequences revealed that strain HN-E23T formed a distinct phylogenetic lineage within the cluster comprising Erythrobacter strains. Strain HN-E23T shared the highest 16S rRNA gene sequence similarity to Erythrobacter aquimixticola JSSK-14T (97.2 %), followed by Erythrobacter atlanticus s21-N3T (96.6 %), Erythrobacter luteus KA37T (96.5 %) and Erythrobacter citreus RE35F/1T (96.4 %). The digital DNA–DNA hybridization (dDDH) and the average nucleotide identity (ANI) values between strain HN-E23T and JSSK-14T were 18.8 and 74.9 %, respectively. The dDDH and ANI values are below the standard cut-off criteria for delineation of bacterial species. The dominant fatty acids were summed feature 8 (C18 : 1ω7c/ω6c), C16 : 0 and summed feature 3 (C16 : 1ω7c/ω6c). The major polar lipids comprised phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, sphingoglycolipid, an unidentified glycolipid and six unidentified lipids. The respiratory lipoquinone was identified as Q-10. The G+C content of the genomic DNA was 65.5 mol%. Based on the phenotypic and phylogenetic data, strain HN-E23T represents a novel species of the genus Erythrobacter , for which the name Erythrobacter spongiae sp. nov. is proposed, with the type strain HN-E23T (=MCCC 1K03331T=LMG 30457T).

A Comparison of 14 Erythrobacter Genomes Provides Insights into the Genomic Divergence and Scattered Distribution of Phototrophs

Aerobic anoxygenic phototrophic bacteria (AAPB) are bacteriochlorophyll a (Bchl a)-containing microbial functional population. Erythrobacter is the first genus that was identified to contain AAPB species. Here, we compared 14 Erythrobacter genomes: seven phototrophic strains and seven non- phototrophic strains. Interestingly, AAPB strains are scattered in this genus based on their phylogenetic relationships. All 14 strains could be clustered into three groups based on phylo-genomic analysis, average genomic nucleotide identity and the phylogeny of signature genes (16S rRNA and virB4 genes). The AAPB strains were distributed in three groups, and gain and loss of phototrophic genes co-occurred in the evolutionary history of the genus Erythrobacter. The organization and structure of photosynthesis gene clusters (PGCs) in seven AAPB genomes displayed high synteny of major regions except for few insertions. The 14 Erythrobacter genomes had a large range of genome sizes, from 2.72 to 3.60 M, and the sizes of the core and pan- genomes were 1231 and 8170 orthologous clusters, respectively. Integrative and conjugative elements (ICEs) were frequently identified in genomes we studied, which might play significant roles in shaping or contributing to the pan-genome of Erythrobacter. Our findings suggest the ongoing evolutionary divergence of Erythrobacter genomes and the scattered distribution characteristic of PGC.

Erythrobacter atlanticus sp. nov., a bacterium from ocean sediment able to degrade polycyclic aromatic hydrocarbons

A Gram-stain-negative, motile, rod-shaped, orange-pigmented bacterium able to degrade polycyclic aromatic hydrocarbons was isolated from deep-sea sediment of the Atlantic Ocean and subjected to a polyphasic taxonomic study. The strain, designated s21-N3T, could grow at 4–37 °C (optimum 28 °C), at pH 5–10 (optimum pH 7–8) and with 1–7 % (w/v) NaCl (optimum 2–3 %). Strain s21-N3T was positive for nitrate reduction, denitrification, aesculin hydrolysis, oxidase and catalase, but negative for indole production and urease. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain s21-N3T formed a distinct branch within the genus Erythrobacter, sharing high similarities with three closely related strains, Erythrobacter marinus HWDM-33T (98.67 %), ‘Erythrobacter luteus’ KA37 (97.80 %) and Erythrobacter gangjinensis K7-2T (97.59 %). The similarities between strain s21-N3T and other type strains of recognized species within the genus Erythrobacter ranged from 95.00 to 96.47 %. The digital DNA–DNA hybridization values and average nucleotide identity (ANI) values between strain s21-N3T and the three closely related strains Erythrobacter marinus HWDM-33T, ‘Erythrobacter luteus’ KA37 and Erythrobacter gangjinensis K7-2T were 18.60, 18.00 and 18.50 % and 74.24, 72.49 and 72.54 %, respectively. The principal fatty acids were summed feature 8 (C18 : 1ω7c/ω6c) and summed feature 3 (C16 : 1ω7c/ω6c). The respiratory lipoquinone was identified as Q-10. The major polar lipids comprised sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine and diphosphatidylglycerol. The G+C content of the chromosomal DNA was determined to be 58.18 mol%. The combined genotypic and phenotypic distinctiveness demonstrated that strain s21-N3T represents a novel species of the genus Erythrobacter, for which the name Erythrobacter atlanticus sp. nov. is proposed, with the type strain s21-N3T ( = MCCC 1A00519T = KCTC 42697T).

Cultivation-dependent and cultivation-independent characterization of hydrocarbon-degrading bacteria in Guaymas Basin sediments

Marine hydrocarbon-degrading bacteria perform a fundamental role in the biodegradation of crude oil and its petrochemical derivatives in coastal and open ocean environments. However, there is a paucity of knowledge on the diversity and function of these organisms in deep-sea sediment. Here we used stable-isotope probing (SIP), a valuable tool to link the phylogeny and function of targeted microbial groups, to investigate polycyclic aromatic hydrocarbon (PAH)-degrading bacteria under aerobic conditions in sediments from Guaymas Basin with uniformly labeled [¹³C]-phenanthrene (PHE). The dominant sequences in clone libraries constructed from ¹³C-enriched bacterial DNA (from PHE enrichments) were identified to belong to the genus Cycloclasticus. We used quantitative PCR primers targeting the 16S rRNA gene of the SIP-identified Cycloclasticus to determine their abundance in sediment incubations amended with unlabeled PHE and showed substantial increases in gene abundance during the experiments. We also isolated a strain, BG-2, representing the SIP-identified Cycloclasticus sequence (99.9% 16S rRNA gene sequence identity), and used this strain to provide direct evidence of PHE degradation and mineralization. In addition, we isolated Halomonas, Thalassospira, and Lutibacterium sp. with demonstrable PHE-degrading capacity from Guaymas Basin sediment. This study demonstrates the value of coupling SIP with cultivation methods to identify and expand on the known diversity of PAH-degrading bacteria in the deep-sea.

Erythrobacter luteus sp. nov., isolated from mangrove sediment

A Gram-staining-negative, orange-pigmented, aerobic bacterial strain, designated KA37T, was isolated from a mangrove sediment sample collected from Yunxiao mangrove National Nature Reserve, Fujian Province, China. Growth was observed at 4-37 °C, 0-3% (w/v) NaCl and pH 5-10. Mg2+ ions were required for growth. Phylogenetic analysis based on 16S rRNA gene sequencing revealed that the isolate was a member of the genus Erythrobacter, which belongs to the family Erythrobacteraceae. Strain KA37T was most closely related to Erythrobacter gangjinensis KCTC 22330T (96.9% sequence similarity), followed by Erythrobacter marinus KCTC 23554T (96.8%); similarity to other members of the genus was below 96.6%. The major fatty acids were C17 : 1ω6c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). Strain KA37T did not produce bacteriochlorophyll a. The predominant respiratory quinone was ubiquinone 10 (Q-10). The polar lipids of strain KA37T were sphingoglycolipid, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, five unknown lipids and one unidentified phospholipid. According to its morphology, physiology, fatty acid composition and 16S rRNA sequence, the novel strain most appropriately belongs to the genus Erythrobacter, but can be distinguished readily from species of the genus Erythrobacter with validly published names. The name Erythrobacter luteus sp. nov. is proposed, with strain KA37T ( = MCCC 1F01227T = KCTC 42179T) as the type strain.

Erythrobacter lutimaris sp. nov., isolated from a tidal flat sediment

A Gram-stain-negative, non-motile, coccoid- or oval-shaped bacterial strain, designated S-5T, belonging to the class Alphaproteobacteria , was isolated from a tidal flat sediment of the Yellow Sea, Korea and was subjected to a polyphasic taxonomic study. Strain S-5T grew optimally at pH 7.0–8.0, at 30 °C and in the presence of 2–3 % (w/v) NaCl. Neighbour-joining analysis based on 16S rRNA gene sequences showed that strain S-5T fell within the clade comprising the species of the genus Erythrobacter , clustering with the type strains of Erythrobacter pelagi , Erythrobacter citreus and Erythrobacter seohaensis with which it exhibited the highest 16S rRNA gene sequence similarity (96.0–96.7 %). The DNA G+C content was 66.0 mol%. Strain S-5T contained Q-10 as the predominant ubiquinone and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C17 : 1ω6c as the major fatty acids. The major polar lipids were sphingoglycolipid, phosphatidylcholine, phosphatidylglycerol, an unidentified glycolipid and two unidentified lipids. Differential phenotypic properties, together with the phylogenetic and genetic distinctiveness, demonstrated that strain S-5T is distinguishable from other species of the genus Erythrobacter . On the basis of the data presented, strain S-5T is considered to represent a novel species of the genus Erythrobacter , for which the name Erythrobacter lutimaris sp. nov. is proposed. The type strain is S-5T ( = KCTC 42109T = CECT 8624T).

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)).