Genus Sphingobium Research Articles

The lactonase BxdA mediates metabolic specialisation of maize root bacteria to benzoxazinoids

Root exudates contain specialised metabolites that shape the plant’s root microbiome. How host-specific microbes cope with these bioactive compounds, and how this ability affects root microbiomes, remains largely unknown. We investigated how maize root bacteria metabolise benzoxazinoids, the main specialised metabolites of maize. Diverse and abundant bacteria metabolised the major compound in the maize rhizosphere MBOA (6-methoxybenzoxazolin-2(3H)-one) and formed AMPO (2-amino-7-methoxy-phenoxazin-3-one). AMPO forming bacteria were enriched in the rhizosphere of benzoxazinoid-producing maize and could use MBOA as carbon source. We identified a gene cluster associated with AMPO formation in microbacteria. The first gene in this cluster, bxdA encodes a lactonase that converts MBOA to AMPO in vitro. A deletion mutant of the homologous bxdA genes in the genus Sphingobium, did not form AMPO nor was it able to use MBOA as a carbon source. BxdA was identified in different genera of maize root bacteria. Here we show that plant-specialised metabolites select for metabolisation-competent root bacteria. BxdA represents a benzoxazinoid metabolisation gene whose carriers successfully colonize the maize rhizosphere and thereby shape the plant’s chemical environmental footprint.

Sphingobium cyanobacteriorum sp. nov., isolated from fresh water.

A novel Gram-stain-negative, yellow-pigmented, short rod-shaped bacterial strain, HBC34T, was isolated from a freshwater sample collected from Daechung Reservoir, Republic of Korea. The results of 16S rRNA gene sequence analysis indicated that HBC34T was affiliated with the genus Sphingobium and shared the highest sequence similarity to the type strains of Sphingobium vermicomposti (98.01 %), Sphingobium psychrophilum (97.87 %) and Sphingobium rhizovicinum (97.59 %). The average nucleotide identity (ANI) and digital DNA-DNA hybridisation (dDDH) values between HBC34T and species of the genus Sphingobium with validly published names were below 84.01 and 28.1 %, respectively. These values were lower than the accepted species-delineation thresholds, supporting its recognition as representing a novel species of the genus Sphingobium. The major fatty acids (>10 % of the total fatty acids) were identified as summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The main polar lipids were phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, two phospholipids and two unidentified polar lipids. The respiratory quinone was Q-10. The genomic DNA G+C content of HBC34T was 64.04 %. The polyphasic evidence supports the classification of HBC34T as the type strain of a novel species of the genus Sphingobium, for which the name Sphingobium cyanobacteriorum sp. nov is proposed. The type strain is HBC34T (= KCTC 8002T= LMG 33140T).

Sphingobium sp. V4, a bacterium degrading multiple allelochemical phenolic acids

BackgroundContinuous cropping challenges constrain the development of agriculture. Three main obstacles limit continuous cropping: autotoxicity of plant allelochemicals, deterioration of physicochemical characteristics of soil, and microflora imbalance. Plant-derived phenolic acids can cause autotoxicity, which is considered the main factor mediating continuous cropping obstacles. Reducing the phenolic acids in continuous cropping soils can decrease the autotoxicity of phenolic acids and ameliorate continuous cropping obstacles. Therefore, it is important to study the microbial resources that degrade allelochemical phenolic acids. Thus, the bacterial strain V4 that can degrade phenolic acids was isolated, identified, and genomically analyzed.ResultsStrain V4 isolated from strawberry soil using vanillic acid-mineral agar was identified as a Gram-negative short rod bacterium. Subsequent 16S rRNA phylogenetic analysis revealed that V4 clustered with members of the genus Sphingobium. The most closely related species were Sphingobium lactosutens DS20T (99% similarity) and Sphingobium abikonense NBRC 16140T (97.5% similarity). V4 also shared > 95% sequence similarity with other members of Sphingobium, so Sphingobium sp. V4 was named accordingly. Biochemical tests revealed that the biochemical characteristics of Sphingobium sp. V4 were similar to its most similar strains except for some properties. Sphingobium sp. V4 effectively degraded vanillic acid, ferulic acid, p-coumaric acid, p-hydroxybenzoic acid, and syringic acid. V4 grew best at the conditions of 30 °C, pH 6.0–7.0, and 0–0.05% NaCl. 500 mg/L vanillic acid was completely degraded by V4 within 24 h under the optimal conditions. Whole genome analysis showed that Sphingobium sp. V4 contained one chromosome and three plasmids. Two genes involved in vanillic acid degradation were found in the V4 genome: the gene encoding vanillate O-demethylase oxidoreductase VanB on the chromosome and the gene encoding vanillate monooxygenase on a large plasmid. The organization of vanillate catabolic genes differed from the adjacent organization of the genes, encoding vanillate o-demethylase VanA and VanB subunits, in Pseudomonas and Acinetobacter.ConclusionsThe isolated bacterium Sphingobium sp. V4 degraded multiple phenolic acids. Its properties and genome were further analyzed. The study provides support for further investigation and application of this phenolic acid-degrading microorganism to alleviate continuous cropping obstacles in agriculture.

Sphingobium agri sp. nov., isolated from rhizospheric soil of eggplant.

A Gram-stain-negative, aerobic, short rod-shaped and motile bacterial strain, designated MAH-33T, was isolated from rhizospheric soil of eggplant. The colonies were observed to be yellow-coloured, smooth, spherical and 0.1-0.3 mm in diameter when grown on TSA agar medium for 2 days. Strain MAH-33T was found to be able to grow at 10-40 °C, at pH 5.0-10.0 and at 0-3.0 % NaCl (w/v). The strain was found to be positive for both oxidase and catalase tests. The strain was positive for hydrolysis of tyrosine and aesculin. According to the 16S rRNA gene sequence comparisons, the isolate was identified as a member of the genus Sphingobium and to be closely related to Sphingobium quisquiliarum P25T (98.4 % similarity), Sphingobium mellinum WI4T (97.8 %), Sphingobium fuliginis TKPT (97.3 %) and Sphingobium herbicidovorans NBRC 16415T (96.9 %). The novel strain MAH-33T has a draft genome size of 3 908 768 bp (28 contigs), annotated with 3689 protein-coding genes, 45 tRNA and three rRNA genes. The average nucleotide identity and digital DNA-DNA hybridization values between strain MAH-33T and closely related type strains were in the range of 79.8-81.6 % and 23.2-24.5 %, respectively. The genomic DNA G+C content was determined to be 62.2 %. The predominant isoprenoid quinone was ubiquinone 10. The major fatty acids were identified as C16 : 0 and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The polar lipids identified in strain MAH-33T were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, sphingoglycolipid, phosphatidylcholine; one unknown phospholipid and one unknown lipid. On the basis of digital DNA-DNA hybridization, ANI value, genotypic analysis, chemotaxonomic and physiological data, strain MAH-33T represents a novel species within the genus Sphingobium, for which the name Sphingobium agri sp. nov. is proposed, with MAH-33T (=KACC 19973T = CGMCC 1.16609T) as the type strain.

Sphingobium lignivorans sp. nov., isolated from river sediment downstream of a paper mill.

A bacterial isolate, B1D3AT, was isolated from river sediment collected from the Hiwassee River near Calhoun, TN, by enrichment culturing with a model 5-5' lignin dimer, dehydrodivanillate, as its sole carbon source. B1D3AT was also shown to utilize several model lignin-derived monomers and dimers as sole carbon sources in a variety of minimal media. Cells were Gram-stain-negative, aerobic, motile, rod-shaped and formed yellow/cream-coloured colonies on rich agar. Optimal growth occurred at 30 °C, pH 7-8, and in the absence of NaCl. The major fatty acids of B1D3AT were C18 : 1 ω7c and C17 : 1 ω6c. The predominant hydroxy fatty acids were C14 : 0 2-OH and C15 : 0 2-OH. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidyldimethylethanolamine and sphingoglycolipid. B1D3AT contained spermidine as the only major polyamine. The major isoprenoid quinone was Q-10 with minor amounts of Q-9 and Q-11. The genomic DNA G+C content of B1D3AT was 65.6 mol%. Phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of 49 core, universal genes defined by Clusters of Orthologous Groups gene families indicated that B1D3AT was a member of the genus Sphingobium. B1D3AT was most closely related to Sphingobium sp. SYK-6, with a 100 % 16S rRNA gene sequence similarity. B1D3AT showed 78.1-89.9 % average nucleotide identity and 19.5-22.2% digital DNA-DNA hybridization identity with other type strains from the genus Sphingobium. On the basis of phenotypic and genotypic properties and phylogenetic inference, strain B1D3AT should be classified as representing a novel species of the genus Sphingobium, for which the name Sphingobium lignivorans sp. nov. is proposed. The type strain is strain B1D3AT (ATCC TSD-279T=DSM 111877T).

Combined Omics Approach Reveals Key Differences between Aerobic and Microaerobic Xylene-Degrading Enrichment Bacterial Communities: Rhodoferax─A Hitherto Unknown Player Emerges from the Microbial Dark Matter.

Among monoaromatic hydrocarbons, xylenes, especially the ortho and para isomers, are the least biodegradable compounds in oxygen-limited subsurface environments. Although much knowledge has been gained regarding the anaerobic degradation of xylene isomers in the past 2 decades, the diversity of those bacteria which are able to degrade them under microaerobic conditions is still unknown. To overcome this limitation, aerobic and microaerobic xylene-degrading enrichment cultures were established using groundwater taken from a xylene-contaminated site, and the associated bacterial communities were investigated using a polyphasic approach. Our results show that the xylene-degrading bacterial communities were distinctly different between aerobic and microaerobic enrichment conditions. Although members of the genus Pseudomonas were the most dominant in both types of enrichments, the Rhodoferax and Azovibrio lineages were only abundant under microaerobic conditions, while Sphingobium entirely replaced them under aerobic conditions. Analysis of a metagenome-assembled genome of a Rhodoferax-related bacterium revealed aromatic hydrocarbon-degrading ability by identifying two catechol 2,3-dioxygenases in the genome. Moreover, phylogenetic analysis indicated that both enzymes belonged to a newly defined subfamily of type I.2 extradiol dioxygenases (EDOs). Aerobic and microaerobic xylene-degradation experiments were conducted on strains Sphingobium sp. AS12 and Pseudomonas sp. MAP12, isolated from the aerobic and microaerobic enrichments, respectively. The obtained results, together with the whole-genome sequence data of the strains, confirmed the observation that members of the genus Sphingobium are excellent aromatic hydrocarbon degraders but effective only under clear aerobic conditions. Overall, it was concluded that the observed differences between the bacterial communities of aerobic and microaerobic xylene-degrading enrichments were driven primarily by (i) the method of aromatic ring activation (monooxygenation vs dioxygenation), (ii) the type of EDO enzymes, and (iii) the ability of degraders to respire utilizing nitrate.

Comparative genomics of the plant-growth promoting bacterium Sphingobium sp. strain AEW4 isolated from the rhizosphere of the beachgrass Ammophila breviligulata

BackgroundThe genus Sphingobium within the class Alpha-proteobacteria contains a small number of plant-growth promoting rhizobacteria (PGPR), although it is mostly comprised of organisms that play an important role in biodegradation and bioremediation in sediments and sandy soils. A Sphingobium sp. isolate was obtained from the rhizosphere of the beachgrass Ammophila breviligulata with a variety of plant growth-promoting properties and designated as Sphingobium sp. strain AEW4.ResultsAnalysis of the 16S rRNA gene as well as full genome nucleotide and amino acid identities revealed that this isolate is most similar to Sphingobium xenophagum and Sphingobium hydrophobicum. Comparative genomics analyses indicate that the genome of strain AEW4 contains unique features that explain its relationship with a plant host as a PGPR, including pathways involved in monosaccharide utilization, fermentation pathways, iron sequestration, and resistance to osmotic stress. Many of these unique features are not broadly distributed across the genus. In addition, pathways involved in the metabolism of salicylate and catechol, phenyl acetate degradation, and DNA repair were also identified in this organism but not in most closely related organisms.ConclusionThe genome of Sphingobium sp. strain AEW4 contains a number of distinctive features that are crucial to explain its role as a plant-growth promoting rhizobacterium, and comparative genomics analyses support its classification as a relevant Sphingobium strain involved in plant growth promotion of beachgrass and other plants.

Orizontal transfer of haloalkane dehalogenase (LinB) gene among novel hexachlorocyclohexane (HCH) degrading sphingomonads isolated from contaminated soil

Soil samples from a HCH dump site and agricultural fields were collected from northern part of India in order to determine residue levels of a-, b-, g- and d- HCH and distribution of HCH degrading sphingomonads. The concentration of HCH residues was found to be very high in dump site soil (upto 4252.47µg/g) but it was low in the soil collected from the agricultural lands (upto 7.7µg/g). Eight novel HCH degrading strains could be isolated from HCH dump site soil but none from agricultural soil. Southern blot hybridization studies revealed the presence of haloalkane dehalogenase (LinB) genes alongwith IS6100 mobile genetic element in all of these strains. Further, 16S rDNA based phylogenetic analysis showed that these strains belong to the genus Sphingobium of family sphingomonadacae. An evidence for horizontal transfer of linB gene among these novel sphingomonads (only five were analysed) was derived by phylogenetic incongruency based approach. The sequence analysis of linB gene of novel isolates showed high sequence similarity (>98.9 to 100%) with each other indicating they were the homologs of same gene. Comparison of “species tree” with “linB gene tree” revealed incongruency among both the trees thus proving that this gene has disseminated among these novel sphingomonads in a recent HGT event. Presence of IS6100 element in all the strains further supported the evidence. This study reveals that the members of family sphingomonadacae are acquiring lin genes by horizontal transfer under high selective pressure of HCH and such phenomenon at a contaminated site is quite significant for bioremediation of HCH.

Cometabolic benzo[a]pyrene biotransformation by Sphingobium barthaii KK22 proceeds through the kata-annelated ring and 1-pyrenecarboxylic acid to downstream products.

Benzo[a]pyrene is a hazardous environmental pollutant that is resistant to bacterial biodegradation and biotransformation pathway development has not been advanced. Considering this, cometabolic benzo[a]pyrene biotransformation by a member of the genus Sphingobium was investigated by cell growth on phenanthrene as a carbon and energy source in conjunction with comparative analyses of culture extracts by gas chromatography (GC) and liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Under these culture conditions, approximately 20% of 100 mg/L benzo[a]pyrene (apparent solubility) was biodegraded in 14 days and benzo[a]pyrene biotransformation products were detected and identified to be extradiol and intradiol ring-cleavage products of the benzo[a]pyrene kata-annelated ring. The o‑hydroxy-tetraaromatic acids, 2-hydroxypyrene-1-carboxylic acid, and 1-hydroxypyrene-2-carboxylic acid were identified in addition to 7,8- and 9,10-dihydroxy-benzo[a]pyrenes, carboxyvinylpyrene-carboxylic acids, hydroxypyrene-oxobutenoic acids, pyrene-1,2-dicarboxylic acid, 1,2-dihydroxypyrene and different oxophenalene compounds. 1-Pyrenecarboxylic acid and other ring-opened oxidized compounds were identified as novel benzo[a]pyrene biodegradation products. In separate assays, 2-hydroxypyrene-1-carboxylic acid was found to be produced from 1-pyrenecarboxylic acid and these results reshaped our understanding of bacterial benzo[a]pyrene biotransformation pathways. Overall, the identities of thirteen products were proposed and new benzo[a]pyrene biodegradation pathways were constructed from experimental chemical evidence. This work extends our understanding of benzo[a]pyrene biotransformation by gram-negative bacteria.

Heterologous expression of a novel serine palmitoyltransferase from Sphingobium chungbukense

In the described experiments, we identify and clone a novel serine palmitoyltransferase (SPT) isolated from the gram-negative obligatory aerobic bacteria Sphingobium chungbukense strain KCTC2955. SPT catalyzes the first rate-limiting reaction in the de novo biosynthesis of sphingolipids, in S. chungbukense. The DNA sequence of the cloned SPT gene (1791 bp) has an open reading frame encoding 405 amino acids with a predicted molecular mass of 41 kDa; the sequence contains the consensus PLP-binding motif (GTFSKSXXXXGG) which is conserved among serine palmitoyltransferase. The ribosomal binding site GGGA lays 6 bp upstream of the ORF of 1218 bp, which is initiated by an ATG codon and terminated by TGA. The cloned SPT gene succeeded in overproducing the SPT protein under the T7 promoter of the expression vector pET 21a in Escherichia coli BL21(DE3), in which the product amounted to about 20–30% of the total protein isolated from the cell extract. Sphingobium SPT showed about a 68.4–89.3% homology with other enzymes in the serine palmitoyltransferase family, and amino acid residues proposed to be involved in catalysis were conserved. The activity of purified recombinant-SPT using Ni-NTA metal-affinity chromatography was measured via the radioactivity of the [3H]-3-ketodihydrosphingosone (KDS) formation using l-[3H]-serine. We have identified a novel SPT gene from S. chungbukense KCTC2955 and overexpressed the recombinant SPT in E. coli. This study is a first step in understanding the reaction mechanism of SPT in bacteria as well as the first focused on the genus Sphingobium.

Phylogenetic farming: Can evolutionary history predict crop rotation via the soil microbiome?

Agriculture has long employed phylogenetic rules whereby farmers are encouraged to rotate taxonomically unrelated plants in shared soil. Although this forms a central tenet of sustainable agriculture, strangely, this on‐farm “rule of thumb” has never been rigorously tested in a scientific framework. To experimentally evaluate the relationship between phylogenetic distance and crop performance, we used a plant–soil feedback approach whereby 35 crops and weeds varying in their relatedness to tomato (Solanum lycopersicum) were tested in a two‐year field experiment. We used community profiling of the bacteria and fungi to determine the extent to which soil microbes contribute to phenotypic differences in crop growth. Overall, tomato yield was ca. 15% lower in soil previously cultivated with tomato; yet, past the species level there was no effect of phylogenetic distance on crop performance. Soil microbial communities, on the other hand, were compositionally more similar between close plant relatives. Random forest regression predicted log10 phylogenetic distance to tomato with moderate accuracy (R 2 = .52), primarily driven by bacteria in the genus Sphingobium. These data indicate that, beyond avoiding conspecifics, evolutionary history contributes little to understanding plant–soil feedbacks in agricultural fields; however, microbial legacies can be predicted by species identity and relatedness.

Sphingobium algorifonticola sp. nov., isolated from a cold spring.

Strain TLA-22T, isolated from a cold spring in Taiwan, was characterized using a polyphasic taxonomy approach. Cells were Gram-stain-negative, aerobic, poly-β-hydroxybutyrate-accumulating, motile by means of a single polar flagellum, rod-shaped and formed bright yellow colonies. Optimal growth occurred at 20-25 °C, pH 6-6.5, and in the presence of 0.5 % NaCl. The major fatty acids of TLA-22T were C18 : 1 ω7 c and C17 : 1ω6c. The predominant hydroxy fatty acids were C15 : 0 2-OH and C14 : 0 2-OH. The polar lipid profile consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidyldimethylethanolamine, sphingoglycolipid, an unidentified aminophospholipid, an unidentified phospholipid and three unidentified lipids. TLA-22T contained spermidine as the major polyamine and putrescine as the minor component. The only isoprenoid quinone was Q-10. The genomic DNA G+C content of TLA-22T was 63.2 mol%. Phylogenetic analyses based on 16S rRNA gene sequences and coding sequences of 92 protein clusters indicated that TLA-22T was a mem,ber of a phylogenetic lineage including members of the genus Sphingobium. TLA-22T was most closely related to Sphingobium aromaticiconvertens RW16T, with a 97.4 % 16S rRNA gene sequence similarity. TLA-22T showed 74.8-75.7 % average nucleotide identity and 20.1-22.0 % digital DNA-DNA hybridization identity with the strains of other species of the genus Sphingobium. On the basis of phenotypic and genotypic properties and phylogenetic inference, strain TLA-22T should be classified as representing a novel species of the genus Sphingobium, for which the name Sphingobium algorifonticola sp. nov. is proposed. The type strain is TLA-22T (=BCRC 81097T =LMG 30309T=KCTC 62189T).

Whole genome sequences reveal the presence of 11 heterotypic synonyms in the genus Sphingobium and emended descriptions of Sphingobium indicum, Sphingobium fuliginis, Sphingobium xenophagum and Sphingobium cupriresistens.

Phylogenetic analysis based on 16S rRNA gene sequences of the genus Sphingobium showed the presence of four distinguishable clusters, in each of which the species shared almost the same evolutionary distance. They were Sphingobium indicum, Sphinogbium lucknowense, Sphinogbium chinhatense, Sphinogbium francense and Sphinogbium japonicum in cluster I, Sphinogbium barthaii and Sphinogbium fuliginis in cluster II, Sphinogbium hydrophobicum and Sphinogbium xenophagum in cluster III and Sphinogbium czechense and Sphinogbium cupriresistens in cluster IV. The 16S rRNA gene sequence similarities between the species in each cluster were all higher than 98 %. Genome-based average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) relatedness values between the species of each cluster were all higher than the threshold values of 95-96 % ANI and 70 % dDDH for species discrimination, respectively, suggesting that each cluster represents only one species of the genus Sphingobium. Due to priority of publication, S. lucknowense, S. chinhatense, S. francense and S. japonicum should be taken as later heterotypic synonyms of S. indicum, S. barthaii as a later heterotypic synonym of S. fuliginis, S. hydrophobicum as a later heterotypic synonym of S. xenophagum and S. czechense as a later heterotypic synonym of S. cupriresistens. Correspondingly, the descriptions of S. indicum, S. fuliginis, S. xenophagum and S. cupriresistens are also emended based on this study.

Sphingobium terrigena sp. nov., isolated from gasoline-contaminated soil.

A Gram-stain-negative, strictly aerobic bacterial strain, designated EO9T, was isolated from gasoline-contaminated soil in the Republic of Korea. Cells were non-motile short rods showing catalase- and oxidase-positive reactions. Growth was observed at 10-37 °C (optimum, 30 °C), at pH 6.0-9.0 (pH 6.5) and in the presence of 0-0.5 % (w/v) NaCl (0 %). Ubiquinone-10 (Q-10) and spermidine were identified as the predominant respiratory quinone and polyamine, respectively. Summed feature 8 (comprising C18:1ω7c/C18:1ω6c), summed feature 3 (comprising C16:1ω7c/C16:1ω6c), C16:0 and C14:0 2-OH were identified as major cellular fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid, phosphatidylglycerol and an unidentified phospholipid. The G+C content of the genomic DNA was 62.8 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain EO9T formed a tight phylogenetic lineage with Sphingobium xenophagum NBRC 107872T and Sphingobium hydrophobicum C1T within the genus Sphingobium. Strain EO9T was most closely related to S. xenophagum NBRC 107872T (97.2 %) and S. hydrophobicum C1T (97.2 %), but DNA-DNA relatedness levels between strain EO9T and the type strains of S. xenophagum and S. hydrophobicum were 37.1 and 36.8 % , respectively. Based on its phenotypic, chemotaxonomic and molecular features, strain EO9T clearly represents a novel species of the genus Sphingobium, for which the name Sphingobium terrigena sp. nov. is proposed. The type strain is EO9T (=KACC 19523T=JCM 32762T).

Description of Sphingobium psychrophilum sp. nov., a cold-adapted bacterium isolated from Arctic soil.

A yellow-coloured, Gram-stain-negative, non-sporulating, psychrotolerant and motile bacterium, designated AR-3-1T, was isolated from the Arctic soil of Cambridge Bay, Nunavut, Canada. Strain AR-3-1T could grow at 4-32 °C and pH 5.0- 11.0. Phylogenetic analysis based on its 16S rRNA gene sequence indicated that strain AR-3-1T formed a lineage within the family Sphingomonadaceae and clustered as a member of the genus Sphingobium. The closest members within this genus were Sphingobium cupriresistens CU4T (98.1 % sequence similarity), Sphingobium vermicomposti VC-230T (97.6 %) and Sphingobium lactosutens DS20T (97.5 %). The only respiratory quinone was the ubiquinone Q-10. Spermidine was the predominant polyamine. The principal cellular fatty acids were summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c), summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c), C16 : 0 and C14 : 0 2-OH. The major polar lipids were phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, sphingoglycolipid and phosphoglycolipid. The DNA G+C content was 63.1 %. The average nucleotide identity and in silico DNA-DNA hybridization relatedness values between strain AR-3-1T and its most closely related genus members were ≤89.6 and 39.6 %, respectively. The genome was 5 162 327 bp long, with 83 scaffolds and 4824 protein-coding genes. The genome showed six putative biosynthetic gene clusters responsible for various secondary metabolites. Based on this polyphasic study, strain AR-3-1T represents a novel species within the genus Sphingobium, for which the name Sphingobium psychrophilum sp. nov. is proposed. The type strain is AR-3-1T (=KACC 21613T=NBRC 114604T).

Sphingobium chungangianum sp. nov., isolated from rhizosphere of Pinus koraiensis.

A novel Gram-staining negative, yellow-pigmented, non-motile, aerobic and rod-shaped bacterium, designated MAH-11T, was isolated from rhizosphere of Pinus koraiensis and was characterised by using a polyphasic taxonomic approach. The colonies were smooth, circular and 0.3-1.0mm in diameter when grown on R2A agar for 3days. The strain was positive for both catalase and oxidase tests. Optimum growth temperature and pH were 28-30°C and 7.0, respectively. Cell growth occurs on R2A agar, nutrient agar, Luria-Bertani agar and tryptone soya agar but not on MacConkey agar. The novel strain was found to be able to hydrolyse esculin but not casein, gelatin, starch, L-tyrosine, DNA, L-arginine, urea, Tween 20 and Tween 80. On the basis of 16S rRNA gene sequence analysis, strain MAH-11T belongs to the genus Sphingobium and is closely related to Sphingobium quisquiliarum P25T (98.1%), Sphingobium vermicomposti VC-230T (97.8%), Sphingobium mellinum WI4T (97.5%), Sphingobium barthaii KK22T (97.2%) and Sphingobium fuliginis TKPT (97.2%). In DNA-DNA hybridization tests, the DNA relatedness values between strain MAH-11T and its close phylogenetic neighbors were below 45.0%. The DNA G+C content was 64.5mol% and the predominant respiratory quinone was identified as ubiquinone-10. The major cellular 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 DNA-DNA hybridization results in combination with chemotaxonomic and physiological data demonstrated that strain MAH-11T represents a novel species within the genus Sphingobium, for which the name Sphingobium chungangianum is proposed. The type strain is MAH-11T (= KACC 19836T = CGMCC 1.13749T).

Sphingobium pinisoli sp. nov., isolated from the rhizosphere soil of a Korean native pine tree.

A Gram-stain negative, aromatic compound degrading bacterium, designated strain ASA28T, was isolated from the rhizosphere soil of a pine tree at Anmyon island, Taean in Korea. Strain ASA28T was found to be strictly aerobic, non-motile, short rods which can grow at 15-28°C (optimum, 25-28°C), at pH 5.0-11.0 (optimum, pH 7.0) and at salinities of 0-1.0% (w/v) NaCl (optimum, 0% NaCl). Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain ASA28T belongs to the genus Sphingobium, showing high sequence similarity to Sphingobium scionense WP01T (97.8%), Sphingobium vermicocomposti VC-230T (96.8%), Sphingobium yanoikuyae ATCC 51230T (96.5%) and Sphingobium herbicidovorans MHT (95.6%). The predominant ubiquinone and polyamine components were identified as Q-10 and spermidine, respectively. The major fatty acids were identified as C18:1ω7c, C16:0, C14:0 2-OH and C16:1ω7c and/or C15:0 iso 2-OH. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylcholine, sphingoglycolipid, phosphoglycolipid, four unidentified aminophospholipids, an unidentified aminolipid, two unidentified phospholipids and six unidentified lipids. The DNA G+C content of this novel isolate was determined to be 63.0mol%. DNA-DNA relatedness between strain ASA28T and S. herbicidovorans KCTC 2939T, S. vermicocomposti DSM 21299T and S. scionense DSM 19371T was determined to be 32 ± 5%, 30 ± 4% and 25 ± 5%, respectively. On the basis of the phylogenetic, phenotypic and chemotaxonomic analyses in this study, strain ASA28T is considered to represent a novel species of the genus Sphingobium, for which the name Sphingobium pinisoli sp. nov. is proposed. The type strain is ASA28T (= KACC 18700T = NBRC 112246T).

Sphingobium aromaticivastans sp. nov., a novel aniline- and benzene-degrading, and antimicrobial compound producing bacterium.

A strictly aerobic, orange-pigmented strain was isolated and designated as UCM-25T. This strain is capable of degrading aniline and benzene, while is also producing antimicrobial compounds which inhibit the growth of some common pathogenic microbes. A near full-length 16S rRNA gene sequence revealed similarity to Sphingobium chlorophenolicum NBRC 16172T (98.6%). The level of DNA-DNA hybridization between the new isolate and the related species suggests UCM-25T to be a new species belonging to the genus Sphingobium. The bacterial cells contained phosphatidylglycerol, phosphatidylethanolamine, sphingoglycolipid, phosphatidylcholine, phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine, three unidentified polar lipids, and an unidentified aminophospholipid. Ubiquinone Q-10 was the major quinone and spermidine was the major polyamine. The G+C content in the DNA of strain UCM-25T was 62.9mol%. Cells contained summed feature 8 (C18:1ω7c and/or C18:1ω6c), summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0, and C14:0 2-OH as major fatty acids. Based on the comparison of phenotypic, genotypic, and chemotaxonomic characteristics, strain UCM-25T represents a new member of the genus Sphingobium, for which the name S. aromaticivastans sp. nov. is proposed. The type strain is UCM-25T (=KACC 19288T =DSM 105181T).

Quantitative proteomic and transcriptional analyses reveal degradation pathway of γ-hexachlorocyclohexane and the metabolic context in the actinobacterium Streptomyces sp. M7

Highly contaminated γ-hexachlorocyclohexane (lindane) areas were reported worldwide. Low aqueous solubility and high hydrophobicity make lindane particularly resistant to microbial degradation. Physiological and genetic Streptomyces features make this genus more appropriate for bioremediation compared with others. Complete degradation of lindane was only proposed in the genus Sphingobium although the metabolic context of the degradation was not considered. Streptomyces sp.M7 has demonstrated ability to remove lindane from culture media and soils. In this study, we used MS-based label-free quantitative proteomic, RT-qPCR and exhaustive bioinformatic analysis to understand lindane degradation and its metabolic context in Streptomyces sp. M7. We identified the proteins involved in the up-stream degradation pathway. In addition, results demonstrated that mineralization of lindane is feasible since proteins from an unusual down-stream degradation pathway were also identified. Degradative steps were supported by an active catabolism that supplied energy and reducing equivalents in the form of NADPH. To our knowledge, this is the first study in which degradation steps of an organochlorine compound and metabolic context are elucidate in a biotechnological genus as Streptomyces. These results serve as basement to study other degradative actinobacteria and to improve the degradation processes of Streptomyces sp. M7.

Sphingobium aquiterrae sp. nov., a toluene, meta- and para-xylene-degrading bacterium isolated from petroleum hydrocarbon-contaminated groundwater.

A Gram-negative, aerobic, slightly yellow-pigmented bacterium, designated as SKLS-A10T, was isolated from groundwater sample of the 'Siklós' petroleum hydrocarbon contaminated site (Hungary). Phylogenetic analysis based on 16S rRNA gene sequence revealed that strain SKLS-A10T formed a distinct phyletic lineage within the genus Sphingobium. It shared the highest 16S rRNA gene homology with Sphingobium abikonense DSM 23268T (97.29 %), followed by Sphingobium lactosutens DSM 23389T (97.23 %), Sphingobium phenoxybenzoativorans KCTC 42448T (97.16 %) and Sphingobium subterraneum NBRC 109814T (96.74 %). The predominant fatty acids (>5 % of the total) are C18 : 1ω7c, C14 : 0 2-OH, C16 : 1ω7c/iso C15 : 0 2-OH, C17 : 1ω6c and C16 : 0. The major ubiquinone is Q-10. The predominant polyamine is spermidine. The major polar lipids are sphingoglycolipid and diphosphatidylglycerol. The DNA G+C content of strain SKLS-A10T is 65.9 mol%. On the basis of evidence from this taxonomic study using a polyphasic approach, strain SKLS-A10T represents a novel species of the genus Sphingobium for which the name Sphingobiumaquiterrae sp. nov. is proposed. The type strain is SKLS-A10T (=DSM 106441T=NCAIM B. 02634T).