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A ferredoxin protein (AAY72_06850, named FesR) was identified to associate with chromate [Cr(VI)] resistance in

Selenium (Se) is an essential trace element for life. Se reduction has attracted much attention in the microbial Se cycle, but there is less evidence for Se oxidation. In particular, it is unknown whether microorganisms oxidise organic Se(-II). In this study, four strains of bacteria, namely Dyella spp. LX-1 and LX-66, and Rhodanobacter spp. LX-99 and LX-100, isolated from seleniferous soil, were involved in the oxidation of selenomethionine (SeMet), selenocystine (SeCys2), selenourea and Se(0) to selenite (Se(IV)) in pure cultures. The oxidation rates of organic Se were more rapidly than those of Se(0) in liquid media. Then Se(0) and SeMet were used as examples, microbial oxidation was the predominant process for both additional Se(0) and SeMet in sterilised alkaline or acidic soils. The Se(IV) concentrations were significantly higher at pH 8.56 than at pH 5.25. In addition, water-soluble Se (SOLSe) and exchangeable and carbonate-bound Se (EXC-Se) fractions increased dramatically with these four Se-oxidising bacteria in unsterilised seleniferous soil. To our knowledge, this is the first study to find that various bacteria are involved in the oxidation of organic Se to Se oxyanions, bridging the gap of Se redox in the Se biogeochemical cycle.

A Gram-stain-negative, strictly aerobic, motile, yellow, rod-shaped bacterium, designated ZDH117T, was isolated from soilsampled atthe Danxialandformin Guangdong Province, PR China. The 16S rRNA gene sequence of strain ZDH117T had highest similarityvalues to Sphingomonas adhaesiva DSM 7418T (97.5 %), Sphingomonas desiccabilis CP1DT (97.3 %) and Sphingomonas ginsenosidimutans KACC 14949T (97.2 %). However, phylogenetic analyses based on 16S rRNA gene sequences demonstrated that strain ZDH117T clustered with Sphingomonas zeicaulis 541T (96.17 %) and Sphingomonas sanxanigenens DSM 19645T (95.95 %). The genomic average nucleotide identity values of ZDH117T with S. adhaesiva DSM 7418T, S. desiccabilis CP1DTand S. ginsenosidimutans KACC TT were 75.1, 75.2 and 75.0 %, respectively. The G+C content of the genomic DNA was 67.6 mol%. Strain ZDH117T was characterized to have ubiquinone-10 as the predominant respiratory quinone, sym-homospermidine as the major polyamine and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c), C14 : 0-2OH, C16 : 0 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) as the major cellular fatty acids (>5 % of total). The predominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, sphingoglycolipid, an unidentified phospholipid and three unidentified lipids. On the basis of its phenotypic, chemotaxonomic and phylogenetic characteristics, strain ZDH117T represents a novel species of the genus Sphingomonas , for which the name Sphingomonas gilva sp. nov. is proposed. The type strain is ZDH117T (=KCTC 62894T=CCTCCAB 2018262T).

A Gram-stain-negative, single polar flagellum bacterium, WZY27T, was isolated from rhizospheric soil of Araceae plants. The results of phylogenetic analysis based on 16S rRNA gene sequences showed that this strain is closely related to Sphingomonas adhaesiva DSM 7418T (97.2 % similarity), Sphingomonas koreensis KCTC 2883 (97.1 %) and Sphingomonas ginsenosidimutans JCM 17074T (97.0 %). The genomic average nucleotide identity values between strain WZY27T and the above three strains were 75.3, 73.2 and 75.4 %, and the in silico DNA–DNA hybridization values were 19.1 , 20.1 and 20.9 %, respectively. The major fatty acids (>5 %) of strain WZY27T were summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), C16 : 0, C14 : 0 2-OH and C18 : 1 ω7c 11-methyl. The predominant respiratory quinone and polyamine were ubiquinone Q-10 and homospermidine, respectively. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phospholipids, glycolipids, phosphatidylcholine and sphingoglycolipid. The G+C content of the genomic DNA was 68.4 mol%. Based on the results of genotypic, chemotaxonomic and phenotypic characterization, strain WZY27T represents a novel species of the genus Sphingomonas , for which the name Sphingomonas aracearum sp. nov. is proposed. The type strain is WZY27T (=KCTC 62523T=CCTCC AB 2018056T).

Selenium is an essential trace element for humans, animals and microorganisms. Microbial transformations, in particular, selenium dissimilatory reduction and bioremediation applications have received increasing attention in recent years. This review focuses on multiple Se-reducing pathways under anaerobic and aerobic conditions, and the phylogenetic clustering of selenium reducing enzymes that are involved in these processes. It is emphasized that a selenium reductase may have more than one metabolic function, meanwhile, there are several Se(VI) and/or Se(IV) reduction pathways in a bacterial strain. It is noted that Se(IV)-reducing efficiency is inconsistent with Se(IV) resistance in bacteria. Moreover, we discussed the links of selenium transformations to biogeochemical cycling of other elements, roles of Se-reducing bacteria in soil, plant and digestion system, and the possibility of using functional genes involved in Se transformation as biomarker in different environments. In addition, we point out the gaps and perspectives both on Se transformation mechanisms and applications in terms of bioremediation, Se fortification or dietary supplementation.

Selenium oxyanion reduction is an effective detoxification or/and assimilation processes in organisms, but little is known the mechanisms in aerobic bacteria. Aerobic Comamonas testosteroni S44 reduces Se(VI)/Se(IV) to less-toxic elemental selenium nanoparticles (SeNPs). For Se(VI) reduction, sulfate and Se(VI) reduction displayed a competitive relationship. When essential sulfate reducing genes were respectively disrupted, Se(VI) was not reduced to red-colored SeNPs. Consequently, Se(VI) reduction was catalyzed by enzymes of the sulfate reducing pathway. For Se(IV) reduction, one of the potential periplasm molybdenum oxidoreductase named SerT was screened and further used to analyze Se(IV) reduction. Compared to the wild type and the complemented mutant strain, the ability of Se(IV) reduction was reduced 75% in the deletion mutant ΔserT. Moreover, the Se(IV) reduction rate was significantly enhanced when the gene serT was overexpressed in Escherichia coli W3110. In addition, Se(IV) was reduced to SeNPs by the purified SerT with the presence of NADPH as the electron donor in vitro, showing a Vmax of 61 nmol/min·mg and a Km of 180 μmol/L. A model of Se(VI)/Se(IV) reduction was generated in aerobic C. testosteroni S44. This work provides new insights into the molecular mechanisms of Se(VI)/Se(IV) reduction activities in aerobic bacteria.

Selenium (Se) deficiency in soil is linked to its low content in edible crops, resulting in adverse impacts on the health of 15% of the global population. The crop mainly absorbs oxidized selenate and selenite from soil, then converts them into organic Se. However, the role of Se-oxidizing bacteria in soil Se oxidation, Se bioavailability and Se absorption into plants remains unclear. The strain Agrobacterium sp. T3F4, isolated from seleniferous soil, was able to oxidize elemental Se into selenite under pure culture conditions. The green fluorescent protein (gfp)-gene-marked strain (T3F4-GFP) and elemental Se or selenite (5 mg·kg-1) were added to pak choi (Brassica campestris ssp. chinensis) pot cultures. Observation of the fluorescence and viable counting indicated that GFP-expressing bacterial cells steadily colonized the soil in the pots and the leaves of the pak choi, reaching up to 6.6 × 106 and 2.0 × 105 CFU g-1 at 21 days post cultivation, respectively. Moreover, the total Se content (mostly organic Se) was significantly increased in the pak choi under T3F4 inoculated pot culture, with elemental Se(0) being oxidized into Se(IV), and soil Se(IV) being dissolved before being absorbed by the crop. After strain T3F4 was inoculated, no significant differences in microbial diversity were observed in the soils and roots, whereas the abundance of Rhizobium spp. was significantly increased. To our knowledge, this is the first time that Se-oxidizing Agrobacterium sp. T3F4 has been found to steadily colonize soil and plant tissues, and that its addition to soil increases the absorption of Se in plants. This study provides a potential strategy for Se biofortification.

A Gram-stain-positive, rod-shaped, non-spore-forming bacterium, designated as x-2T, was isolated from lakeside soil of Sayram in the Xinjiang Uygur Autonomous Region, PR China. On the basis of 16S rRNA gene sequences, strain x-2T belongs to the genus Nocardioides in the family Nocardioidaceae , being most closely related to Nocardioides panacisoli Gsoil 346T (97.36 % 16S rRNA gene sequence similarity). Strain x-2T was characterized chemotaxonomically and found to have ll-diaminopimelic acid in the cell-wall peptidoglycan, phosphatidylglycerol, diphosphatidylglycerol, glycolipids and another three unknown phospholipids as the major polar lipids, MK-8(H4) as the predominant menaquinone and C18 : 1ω9c, iso-C16 : 0, C17 : 1ω8c and C16 : 0 as the major fatty acids. The genomic DNA G+C content of the novel strain was 71.1 mol%. The level of DNA–DNA relatedness between strain x-2T and N. panacisoli KCTC 19470T (=Gsoil 346T) was 29.8 %. These chemotaxonomic characters support the position of strain x-2T within the genus Nocardioides . The results of physiological and biochemical tests, as well as phylogenetic analysis, suggest that strain x-2T represents a novel species of the genus Nocardioides , for which the name Nocardioides litorisoli sp. nov. is proposed. The type strain is x-2T (=KCTC 39845T=CCTCCAB 2016255T).

Antibiotic and arsenic (As) contaminations are worldwide public health problems. Previously, the bacterial ABC-type efflux protein MacAB reportedly conferred resistance to macrolide-type antibiotics but not to other metal(loid)s. In this study, the roles of MacAB for the co-resistance of different antibiotics and several metal(loid)s were analyzed in Agrobacterium tumefaciens 5A, a strain resistant to arsenite [As(III)] and several types of antibiotics. The macA and macB genes were cotranscribed, and macB was deleted in A. tumefaciens 5A and heterologously expressed in Escherichia coli AW3110 and E. coli S17-1. Compared to the wild-type strain 5A, the macB deletion strain reduced bacterial resistance levels to several macrolide-type and penicillin-type antibiotics but not to cephalosporin-type antibiotics. In addition, the macB deletion strain showed lower resistance to As(III) but not to arsenate [As(V)], antimonite [Sb(III)] and cadmium chloride [Cd(II)]. The mutant strain 5A-ΔmacB cells accumulated more As(III) than the cells of the wild-type. Furthermore, heterologous expression of MacAB in E. coli S17-1 showed that MacAB was essential for resistance to macrolide, several penicillin-type antibiotics and As(III) but not to As(V). Heterologous expression of MacAB in E. coli AW3110 reduced the cellular accumulation of As(III) but not of As(V), indicating that MacAB is responsible for the efflux of As(III). These results demonstrated that, in addition to macrolide-type antibiotics, MacAB also conferred resistance to penicillin-type antibiotics and As(III) by extruding them out of cells. This finding contributes to a better understanding of the bacterial resistance mechanisms of antibiotics and metal(loid)s.

A Gram-stain-negative, non-motile, rod-shaped, aerobic bacterium, designated HYT19T, was isolated from soil of Mountain Danxia in southern China. It showed the highest similarity of 16S rRNA gene sequence (97.0%) and formed a monophyletic clade with Fibrisoma limi BUZ 3T. Strain HYT19T grew at 16–37 °C (optimum 28–30 °C) and at pH 6–7. The draft genome size of strain HYT19T was 7.8 Mb with a DNA G+C content of 54.0 mol%. The digital DDH and average nucleotide identity values between strain HYT19T and F. limi BUZ 3T were 28.8% and 85.1%, respectively. MK-7 was the sole respiratory quinone. The major polar lipids were phosphatidylethanolamine, unidentified aminophospholipid, two unidentified aminolipids, unidentified phospholipid and unidentified lipid. The strain contained C16:1ω5c, iso-C15:0, summed feature 3 (C16:1ω6c and/or C16:1ω7c), C16:0, iso-C17:0 3-OH and anteiso-C15:0 as the major fatty acids. On the basis of phylogenetic, genomic, phenotypic and chemotaxonomic analysis, we propose a new species Fibrisoma montanum sp. nov. of genus Fibrisoma. The type strain is HYT19T (= CCTCC AB 2018342T = JCM 33105T).

A Gram-reaction-positive, strictly aerobic, capsule-forming, motile and rod-shaped bacterium, designated strain XD80T, was isolated from the soil of a native cave in Lichuan, Hubei province, China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain XD80T was most closely related to Domibacillus iocasae CCTCC AB 2015183T (98.66 % sequence similarity), followed by Domibacillus robiginosus DSM 25058T(97.83 %), Domibacillus tundrae KCTC 33549T (97.70 %), Domibacillus enclensis CCTCC AB 2011121T (97.21 %) and Domibacillus indicus DSM 28032T (96.96 %). Levels of DNA-DNA relatedness between strain XD80T and D. iocasae CCTCC AB 2015183T, D. robiginosusDSM 25058T, D. tundrae KCTC 33549T and D. enclensis CCTCC AB 2011121T were 37.4 %, 53.8 %, 53.6 % and 52.7 %, respectively. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, aminophospholipid and two unknown phospholipids. The predominant fatty acids (>5 %) were iso-C15 : 0 (37.3 %), anteiso-C15 : 0 (10.8 %), C16 : 0 (10.4 %), iso-C17 : 0 (10.3 %), C16 : 1ω11c (9.6 %) and anteiso-C17 : 0 (7.4 %). MK-6 (86.4 %) was the major respiratory quinone. The DNA G+C content was 46.4 mol%. The cell-wall peptidoglycan contained meso-diaminopimelic acid (type A1γ). Ribose and glucose were the major whole-cell sugars. In addition, strain XD80T showed differential physiological characteristics from most members of the genus Domibacillus, encompassing hydrolysis of starch, acid production from inositol and raffinose, and production of valine arylamidase. The results of this polyphasic study indicated that strain XD80T represents a novel species of the genus Domibacillus, for which the name Domibacillus antri sp. nov. is proposed. The type strain is XD80T (=CCTCC AB 2015053T=KCTC 33636T).

Strain DXL2T, a Gram-stain-negative, rod-shaped, endospore-forming, motile, aerobic bacterium, was isolated from selenium mineral soil. DXL2T had the highest 16S rRNA gene sequence similarities with those of Paenibacillus ginsengarvi Gsoil 139T (96.8 %), Paenibacillus hemerocallicola DLE-12T (95.5 %) and Paenibacillus hodogayensis SGT (95.4 %). The genome size of DXL2T was 7.24 Mb, containing 6243 predicted protein-coding genes, with a DNA G+C content of 60.2 mol%. DXL2T contained meso-diaminopimelic acid in the cell-wall peptidoglycan. The major cellular fatty acids were anteiso-C15 : 0, iso-C16 : 0 and iso-C15 : 0. The major quinone was menaquinone 7. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two aminophospholipids, an unidentified aminolipid, phosphatidylmethylethanolamine, an unidentified glycolipid and an unidentified phospholipid. Compared with the other strains, DXL2T had a specific phospholipid and a specific aminolipid, it hydrolyzed Tween 40 and could not assimilate potassium gluconate. On the basis of the phenotypic, chemotaxonomic and phylogenetic results, strain DXL2T represents a novel species within the genus Paenibacillus , for which the name Paenibacillus flagellatus sp. nov. is proposed. The type strain is DXL2T (=KCTC 33976T=CCTCC AB 2018054T).

Elemental selenium nanoparticles (SeNPs) are useful in medicine, environmental remediation and in material science. Biosynthesized SeNPs (BioSeNPs) by bacteria are cheap, eco-friendly and have a lower cytotoxicity in comparison with chemically synthesized ones. Organic matters were found to cap on the surface of BioSeNPs, but the functions were still not entirely clear. The purified BioSeNPs were coated in a thick layer of organic substrates observed by transmission electron microscopy (TEM). Fourier Transform Infrared (FT-IR) and quantitative detection of the coating agents showed that one gram of purified BioSeNPs bound 1069 mg proteins, 23 mg carbohydrates and only very limited amounts of lipids. Proteomics of BioSeNPs showed more than 800 proteins bound to BioSeNPs. Proteins enriched in charged amino acids are the major factor thought to govern the formation process and stabilization of BioSeNPs in bacteria. In view of the results reported here, a schematic model for the molecular mechanism of BioSeNPs formation in bacteria is proposed. These findings are helpful for the artificial green synthesis of stable SeNPs under specific condition and guiding the surface modification of SeNPs for medicine application.

Pseudomonas stutzeri TS44 was able to aerobically reduce Se(IV) into SeNPs and transform Se(IV)/Cd(II) mixture into CdSe-QDs. The SeNPs and CdSe-QDs were systematically characterized by surface feature analyses, and the molecular mechanisms of SeNPs and CdSe-QD formation in P. stutzeri TS44 were characterized in detail. In vivo, under 2.5 mmol/L Se(IV) exposure, GorA was essential for catalyzing of Se(IV) reduction rate decreased by 67% when the glutathione reductase gene gorA was disrupted, but it was not decreased in the glutathione synthesis rate-limiting gene gshA mutated strain compared to the wild type. The complemented strains restored the phenotypes. While under low amount of Se(IV) (0.5 mmol/L), GSH played an important role for Se(IV) reduction. In vitro, GorA catalyzed Se(IV) reduction with NADPH as the electron donor (Vmax of 3.947 ± 0.1061 μmol/min/mg protein under pH 7.0 and 28℃). In addition, CdSe-QDs were successfully synthesized by a one-step method in which Se(IV) and Cd(II) were added to bacterial culture simultaneously. GSH rather than GorA is necessary for CdSe-QD formation in vivo and in vitro. In conclusion, the results provide new findings showing that GorA functions as a selenite reductase under high amount Se(IV) and GSH is essential for bacterial CdSe-QD synthesis.

A Gram-reaction-negative, aerobic, non-motile, red-pigmented and rod-shaped bacterium, designated XF-6RT, was isolated from mountain soil in the Sichuan province of China. Phylogenetic trees based on 16S rRNA gene sequence analysis showed that XF-6RT belonged to the genus Hymenobacter. The greatest 16S rRNA gene sequence similarities of strain XF-6RT were with Hymenobacter soli PB17T (96.4 %) and Hymenobacter saemangeumensis GSR0100T (95.8 %). Summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), iso-C15 : 0, C16 : 1ω5c and anteiso-C15 : 0 were the major fatty acids (>10 %). The only menaquinone was menaquinone-7. The major polar lipids were phosphatidylethanolamine, four aminolipids, four phosphoaminolipids and three lipids. The DNA G+C content was 62 mol%. On the basis of the polyphasic taxonomic analysis, strain XF-6RT is considered to represent a novel species of the genus Hymenobacter, for which the name Hymenobacter monticola sp. nov. is proposed. The type strain is XF-6RT ( = KCTC 42733T = CCTCC AB 2015206T).

Microcalorimetry was used to study the effects of long-term (20 years) fertilization regimes on microbial activities in a paddy soil in southern China derived from infertile land. Managements of phosphorus fertilizer coupled with nitrogen fertilizer significantly promoted the contents of total and available P, mineral N and microbial biomass C (MBC) ( P Q T /MBC) showed that fertilization of P coupled with N, P-deficient fertilization and non-fertilized control significantly separated from each other. Redundancy analysis plot showed that rate of heat output ( Q T /t), peak power ( P max ) and constant of growth rate ( k ) were significantly correlated with soil total and available P, total and mineral N, which were greatly increased by the P fertilizer coupled with N fertilizer. In contrast, Q T /MBC and peak time ( t max ) were greatly increased by the P-deficient treatments. In addition, Q T /t as a new introduced parameter was negatively correlated well with Q T /MBC (R 2 = 0.93, P Q T /MBC, Q T /t and t max are useful to assess soil microbial activity. The higher Q T /t, lower Q T /MBC and t max indicate higher microbial activity and soil quality. In conclusion, long-term fertilization of P coupled with N, especially combined organic fertilizer greatly improved soil fertility and microbial activity; in contrast, deficiency of soil P had lower microbial activity in the paddy soil derived from infertile land.

A Gram-stain-negative, non-motile, rod-shaped, aerobic bacterium, designated strain YLT18T, was isolated from mountain cliff soil of Enshi Grand Canyon in China. The major menaquinone was menaquinone 7 (MK-7) and the predominant fatty acids (>5 %) were iso-C15 : 0, C16 : 1ω5c, iso-C17 : 0 3-OH, summed feature 3 (C16 : 1ω7c/iso-C15 : 0 2-OH) and iso-C15 : 0 3-OH. The major polar lipids were phosphatidylethanolamine, two unknown aminophospholipids, two unknown aminolipids and two unknown polar lipids. The DNA G+C content was 55.4 mol%. According to phylogenetic analysis based on 16S rRNA gene sequences, strain YLT18T was related most closely to Chitinophaga niabensis JS13-10T ( = DSM 24787T) and Chitinophaga cymbidii R156-2T ( = KCTC 23738T), with similarities of 96.7 and 96.2 %, respectively. In addition, strain YLT18T showed obvious differences from the closely related species in terms of esterase (C4) activity, acid production from fructose and rhamnose, and sole carbon source utilization by arabinose and rhamnose. The results from this polyphasic taxonomic study revealed that strain YLT18T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga barathri sp. nov. is proposed. The type strain is YLT18T ( = KCTC 42472T = CCTCC AB 2015054T).

Alishewanella sp. WH16-1 is a facultative anaerobic bacterium isolated from mining soil. Under aerobic conditions, this bacterium efficiently reduces selenite and chromate. A flavoprotein showing 37% amino acid identity to E. coli chromate reductase ChrR was identified from the genome (named CsrF). Gene mutation and complementation along with heterologous expression revealed the ability of CsrF to reduce selenite and chromate in vivo. The purified CsrF was yellow and showed an absorption spectra similar to that of FMN. The molecular weight of CsrF was 23,906 for the monomer and 47,960 for the dimer. In vitro, CsrF catalyzes the reduction of Se(IV) and Cr(VI) using NAD(P)H as cofactors with optimal condition of pH 7.0 and temperature of 30-37°C. This enzyme also catalyze the reduction of sulfate and ferric iron but not arsenate and nitrate. Using NADPH as its electron donor, the Km for the reduction of Se(IV) and Cr(VI) was 204.1±27.91 and 250.6±23.46μmol/L, respectively. Site-directed mutagenesis showed that Arg13 and Gly113 were essential for the reduction of Se(IV) and Cr(VI). The products of the reduction of Se(IV) and Cr(VI) were Se(0)- and Cr(III)-nanoparticles, respectively. To our knowledge, CsrF is a novel and well-characterized bacterial aerobic selenite reductase.

The release of silicon (Si) from and the structural changes to clay minerals (i.e., kaolinite, montmorillonite (Mt), and illite) were investigated after being batch incubated with low-molecular-mass organic acids (i.e., oxalic and citric acids, LMMOA) of varying concentrations (0–0.5 mol L − 1 ) at 25 °C. Two mineral acids (i.e., HCl and H 2 SO 4 ) with varying concentrations were also reacted with Ca-montmorillonite (Ca 2 + -Mt). With increasing reaction time, the Si released from kaolinite and illite reached its maximum level after incubation with the varying LMMOA concentrations for 15 days. Quantities of Si released from the clay minerals with the LMMOA ranged from 0.22 to 114.01 μg mL − 1 (Si). Quantity of Si released with oxalic acid was higher than that with citric acid. The Si released from the clay minerals increased with increasing organic acid concentrations. More Si was released from Mt than from kaolinite and illite when incubated with the same LMMOA concentration. With increasing organic acid concentrations, the X-ray diffraction (XRD) reflection intensities of the Mt weakened, and this trend was more remarkable in the clay treated with oxalic acid than citric acid. However, no relationship between the XRD reflection intensity and the acid concentrations was noticeable in the incubated kaolinite and illite. While incubating with hydrochloric acid (HCl) and sulfate acid (H 2 SO 4 ) for 15 day incubation, amounts of Si released from Ca 2 + -Mt were generally higher than those reacting with organic acids, and more Si was released in the H 2 SO 4 treatment than that of HCl. But the XRD reflection intensities of the Ca 2 + -Mt had no distinctly change compared with those treated with the organic acids.

Strain W126T, a Gram-reaction-positive, spore-forming, rod-shaped, facultatively anaerobic bacterium, motile by means of peritrichous flagella, was isolated from selenium mineral soil in Hubei province of China. 16S rRNA gene sequence analysis demonstrated that this isolate belonged to the genus Paenibacillus , with 97.9 % sequence similarity to Paenibacillus anaericanus MH21T, while compared with the other species of the genus Paenibacillus , the 16S rRNA gene sequence similarities were less than 96.0 %. DNA–DNA hybridization between strain W126T and Paenibacillus anaericanus DSM 15890T was 24 %. The major isoprenoid menaquinone was menaquinone-7. Anteiso-C15 : 0 was the major fatty acid. The DNA G+C content was 42.3 mol%. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unknown aminophospholipids and an unknown lipid. Strain W126T contained A1γ-meso-diaminopimelic acid in the cell-wall peptidoglycan. The phenotypic, chemotaxonomic and genotypic data indicate that strain W126T represents a novel species of the genus Paenibacillus , for which the name Paenibacillus selenii sp. nov. is proposed. The type strain is W126T ( = KCTC 33420T = CCTCC AB 2014003T).

Te(IV) reduction to Te(0) is a detoxification process in bacteria. Elemental Te nanostructures are new materials, however, the functions of them, such as adsorption ability, have not been fully explored. Shinella sp. WSJ-2 is a highly Te(IV)-resistant bacterium with a MIC of 8 mmol/L. It was able to rapidly reduce 0.3 mmol/L Te(IV) to Te nanorods (TeNRs) within 28 h, and its Te(IV) reduction ability was relatively stable after 14 cycles repeatedly. The size of TeNRs ranged from 50 to 120 nm. The surface of TeNRs was mainly enveloped with proteins and lipids. Moreover, the biogenic TeNRs were capable of removing multiple dyes and metals and were effectively recycled with 100 mmol/L NaCl. Adsorption equilibrium isotherms showed that the maximum adsorption amounts were 618.8, 1076.8, 496.3, 179.3, 58.7 and 275.3 mg/g for Methylene Blue, Azure B, Malachite Green, Cd(II), Cu(II) and Pb(II), respectively. In conclusion, this is the first evidence that the genus Shinella is involved in Te(IV) reduction. The strong sorption of cationic dyes and metals onto TeNRs is probably due to the electrostatic interaction. This study showed the potential of Shinella sp. WSJ-2 in the bioremediation of toxic Te(IV) and adsorption removal of multiple dyes and metals by biogenic TeNRs.

Soil samples collected from a long-term (19-year) experimental field with seven treatments were analyzed for fatty acids methyl esters (FAMEs) to determine fertilization regime effects on microbial community structure in sandy loam soils. The amounts of FAMEs in bacteria, actinomycetes, and fungi were highest with the two organic manure (OM)-fertilized treatments (OM and 1/2 OMN – half OM plus half mineral fertilizer), lowest with the NK treatment, and fell in the middle levels with three mineral P-fertilized treatments (NPK, NP and PK) and the control with no fertilizer (CK), with the exception of fungi which showed no significant difference among the five treatments without OM fertilization. Principal component analysis of FAME patterns indicated that NPK was not significantly different from CK, but the two manure-containing treatments and the P-deficiency treatment (NK) were significantly different from CK and NPK. Redundancy analysis plot showed that FAME amounts significantly correlated to soil organic C and total N contents, while soil available P and total P contents, which were greatly decreased by the NK treatment, also had positive and substantial effects on soil microbial FAMEs. The results demonstrated the importance of P fertilization as well as organic manure in maintaining soil microbial biomass and impacting community structure.

A Gram-stain-negative, light pink, non-motile, rod-shaped, aerobic bacterium, designated strain XNV015T, was isolated from soil of a vanadium mine. Phylogenetic analyses based on 16S rRNA gene sequences indicated that it belongs to the genus Pedobacter and was closely related to Pedobacter suwonensis DSM 18130T (96.93 % sequence similarity), Pedobacter alluvionis NWER-II11T (96.66 %), Pedobacter terrae DS-57T (96.54 %), Pedobacter kyungheensis KACC 16221T (96.54 %) and Pedobacter soli KACC 14939T (96.47 %). This strain clearly differed from the closely related species in terms of acid production from rhamnose and ethanol. Menaquinone-7 was the predominant respiratory quinone. The predominant fatty acids included iso-C15 : 0, C16 : 1 ω5c, summed feature 3, iso-C17 : 0 3-OH and C17 : 0 2-OH. The major polar lipids were phosphatidylethanolamine, glycolipids, lipids and aminolipids. The genomic DNA G+C content was 43.8 mol%. The genotypic analysis, biochemical properties, and phenotypic and chemotaxonomic characteristics indicate that strain XNV015T represents a novel species of the genus Pedobacter , for which the name Pedobacter vanadiisoli sp. nov. is proposed. The type strain is XNV015T (=CCTCC AB 2015319T=KCTC 42866T).

The objective of this study was to investigate how the relationships between bacterial communities and organic C (SOC) in topsoil (0–5 cm) are affected by tillage practices [conventional intensive tillage (CT) or no-tillage (NT)] and straw-returning methods [crop straw returning (S) or removal (NS)] under a rice-wheat rotation in central China. Soil bacterial communities were determined by high-throughput sequencing technology. After two cycles of annual rice-wheat rotation, compared with CT treatments, NT treatments generally had significantly more bacterial genera and monounsaturated fatty acids/saturated fatty acids (MUFA/STFA), but a decreased gram-positive bacteria/gram-negative bacteria ratio (G+/G−). S treatments had significantly more bacterial genera and MUFA/STFA, but had decreased G+/G− compared with NS treatments. Multivariate analysis revealed that Gemmatimonas, Rudaea, Spingomonas, Pseudomonas, Dyella, Burkholderia, Clostridium, Pseudolabrys, Arcicella and Bacillus were correlated with SOC, and cellulolytic bacteria (Burkholderia, Pseudomonas, Clostridium, Rudaea and Bacillus) and Gemmationas explained 55.3% and 12.4% of the variance in SOC, respectively. Structural equation modeling further indicated that tillage and residue managements affected SOC directly and indirectly through these cellulolytic bacteria and Gemmationas. Our results suggest that Burkholderia, Pseudomonas, Clostridium, Rudaea, Bacillus and Gemmationas help to regulate SOC sequestration in topsoil under tillage and residue systems.

A novel Gram-stain-negative, strictly aerobic, non-motile, rod-shaped, capsule-forming bacterium, designated strain YLT33T, that formed orange-red colonies was isolated from mountain cliff soil from Enshi Grand Canyon, southwest China. Growth occurred at 4–35 °C (optimum 28 °C) and at pH 6.0–10.0 (optimum 7.0). It showed maximum (99.3 %) 16S rRNA gene sequence similarity and formed a monophyletic clade with Sphingoaurantiacus polygranulatus MC 3718T (=CCTCC 2014274T). The DNA G+C content was 68.5 mol% and strain YLT33T showed a 50.5 % DNA–DNA relatedness value to S. polygranulatus MC 3718T. The major fatty acids (>5 %) were C17 : 1ω6c (40.7 %), C15 : 0 (10.4 %), C15 : 1ω6c (9.4 %), summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH; 8.6 %), C17 : 1ω8c (7.1 %), C18 : 1ω7c (6.1 %), and C15 : 0 2-OH (5.7 %). Ubiquinone-10 was the sole respiratory quinone. The polar lipids of strain YLT33T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid, two unknown glycolipids and one unknown phospholipid. Carotenoids were present in cells. Homospermidine was the major polyamine. In addition, strain YLT33T showed obvious differences from the closely related strain S. polygranulatus MC 3718T with respect to major polar lipids, fatty acids and other morphological, physiological and biochemical characteristics. These results from polyphasic taxonomic studies reveal that strain YLT33T represents a novel species of the genus Sphingoaurantiacus , for which the name Sphingoaurantiacus capsulatus sp. nov. is proposed. The type strain is YLT33T (=CCTCC AB 2015150T=KCTC 42644T).

This study investigates the effectiveness and mechanism of decreasing the bioavailability of Pb in bacterial culture and in pot experiments of Pb-contaminated paddy soil by Alishewanella sp. WH16-1. The WH16-1 strain was isolated from mine soil and exhibited high resistances to many heavy metals, especially to Pb2+ (2070 mg/L) and Cr (VI) (2340 mg/L). During cultivation of the WH16-1 strain with the addition of 100 mg/L Pb2+, Pb2+ was precipitated, and 84.13 % of Pb2+ was removed in 72 h. The precipitant was observed by transmission electron microscopy (TEM) and further confirmed to be PbS by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The WH16-1 strain was incubated in Pb2+-added paddy soil pot experiments for 60 days and compared with the uninoculated Pb2+-added paddy soil. Comparison showed that the exchangeable and carbonate-bound Pb in the paddy soil decreased by 14.04 and 10.69 % (P

A Gram-stain-positive, strictly aerobic, non-motile and rod-shaped bacterial strain, designated YS-17T, was isolated from soil in the Lengshuijiang antimony mine, Hunan Province, China. Comparative 16S rRNA gene sequencing analysis clustered it with Flavihumibacter strains, and strain YS-17T was most closely related to Flavihumibacter cheonanensis WS16T (97.2 % similarity), Flavihumibacter petaseus T41T (96.6 %) and Flavihumibacter solisilvae 3-3T (96.5 %). The level of DNA-DNA relatedness between strain YS-17T and F. cheonanensis JCM 19322T was 35.5±0.1 % (n=2). The major respiratory quinone of strain YS-17T was menaquinone-7 and the major polar lipids were phosphatidylethanolamine, two unidentified lipids, two unidentified amino lipids and phospholipid. The major fatty acids (≥5 %) were iso-C15 : 0, iso-C15 : 1 G, unknown ECL 13.565, iso-C17 : 0 3-OH, C15 : 0, C16 : 1ω5c and anteiso-C15 : 0. The DNA G+C content was 47.8 mol%. Compared with other Flavihumibacter strains, strain YS-17T showed major biophysical and biochemical differences, with the ability to hydrolyse gelatin and to assimilate salicin and l-proline. The results demonstrated that strain YS-17T belongs to the genus Flavihumibacter and represents a novel species, for which the name Flavihumibacter stibioxidans sp. nov. is proposed. The type strain is YS-17T (=CCTCC AB 2016053T=KCTC 52205T).

Considering the extensive functional redundancy in microbial communities and great difficulty in elucidating it based on taxonomic structure, studies on the biogeography of soil microbial activity at large spatial scale are as important as microbial community structure. Eighty-four soil samples were collected across a region from south to north China (about 1,000 km) to address the questions if microbial activity displays biogeographic patterns and what are driving forces. These samples represented different soil types, land use and climate. Redundancy analysis and nonmetric multidimensional scaling clearly revealed that soil microbial activities showed distinct differentiation at different sites over a regional spatial scale, which were strongly affected by soil pH, total P, rainfall, temperature, soil type and location. In addition, microbial community structure was greatly influenced by rainfall, location, temperature, soil pH and soil type and was correlated with microbial activity to some extent. Our results suggest that microbial activities display a clear geographic pattern that is greatly altered by geographic distance and reflected by climate, soil pH and total P over large spatial scales. There are common (distance, climate, pH and soil type) but differentiated aspects (TP, SOC and N) in the biogeography of soil microbial community structure and activity.

Currently there are very few researches on studying the vertical changes of metabolic and thermodynamic properties of microbial communities in freshwater lake sediment. In this work, a multi-channe...

Caulobacter vibrioides T5M6 is a Gram-negative strain that strongly solubilizes selenium (Se) mineral into Se(IV) and was isolated from a selenium mining area in Enshi, southwest China. This strain produces the phytohormone IAA and promotes plant growth. Here we present the genome of this strain containing a large number of genes encoding resistances to copper and antibiotics.

To investigate the influence of different agricultural practices and vegetations on soil microbial activity and diversity, soil samples from different habitats were studied with their microbial activities measured by the microcalorimetric technique. Seven soil samples were collected in Wuhan, China from different locations with primary and regeneration forest, nursery and crop land, and uncultivated land. The number of microorganisms in soils was measured by viable count, and some physicochemical parameters were determined. Power–time curves were recorded for soil samples supplemented with glucose and ammonium sulphate, and the total heat changes of the microbial growth reaction, Q total (Jg −1 ) and the microbial growth rate constant, k (min −1 ) were calculated from the curves. All power–time curves presented typical changes of microbial activity. The curves of soil samples could be divided into two groups differing in agricultural practices and vegetations. The same grouping could also be reached according to the values of peak time ( t max ). The most soil samples showed a higher correlation between the values of k and the counted bacterial numbers. The Q total correlated well with vegetation abundance and probably with microbial diversity. In conclusion, microbial activity of the soil samples determined by microcalorimetry reflected differences in soil vegetation and agricultural management.

Paenirhodobacter enshiensis is a non-photosynthetic species that belongs to family Rhodobacteraceae. Here we report the draft genome sequence of Paenirhodobacter enshiensis DW2-9T and comparison results to the available related genomes. The strain has a 3.4 Mbp genome sequence with G + C content of 66.82 % and 2781 protein-coding genes. It lacks photosynthetic gene clusters and putative proteins necessary in Embden-Meyerhof-Parnas (EMP) pathway, but contains proteins in Entner-Doudoroff (ED) pathway instead. It shares 699 common genes with nine related Rhodobacteraceae genomes, and possesses 315 specific genes. Electronic supplementary material The online version of this article (doi:10.1186/s40793-015-0026-9) contains supplementary material, which is available to authorized users.

Pseudomonas migulae ES3-33 is a Gram-negative strain that strongly reduces Se(IV) and was isolated from a selenium mining area in Enshi, southwest China. Here we present the draft genome of this strain containing potential genes involved in selenite reduction and a large number of genes encoding resistances to copper and antibiotics.

Background: Selenium (Se) is an essential trace element in most organisms but has to be carefully handled since there is a thin line between beneficial and toxic concentrations. Many bacteria have the ability to reduce selenite (Se(IV)) and (or) selenate (Se(VI)) to red elemental selenium that is less toxic. Results: A strictly aerobic bacterium, Comamonas testosteroni S44, previously isolated from metal(loid)-contaminated soil in southern China, reduced Se(IV) to red selenium nanoparticles (SeNPs) with sizes ranging from 100 to 200 nm. Both energy dispersive X-ray Spectroscopy (EDX or EDS) and EDS Elemental Mapping showed no element Se and SeNPs were produced inside cells whereas Se(IV) was reduced to red-colored selenium in the cytoplasmic fraction in presence of NADPH. Tungstate inhibited Se(VI) but not Se(IV) reduction, indicating the Se(IV)-reducing determinant does not contain molybdenum as co-factor. Strain S44 was resistant to multiple heavy and transition metal(loid)s such as Se(IV), As(III), Cu(II), and Cd(II) with minimal inhibitory concentrations (MIC) of 100 mM, 20 mM, 4 mM, and 0.5 mM, respectively. Disruption of iscR encoding a transcriptional regulator negatively impacted cellular growth and subsequent resistance to multiple heavy metal(loid)s. Conclusions: C. testosteroni S44 could be very useful for bioremediation in heavy metal(loid) polluted soils due to the ability to both reduce toxic Se(VI) and Se(IV) to non-toxic Se (0) under aerobic conditions and to tolerate multiple heavy and transition metals. IscR appears to be an activator to regulate genes involved in resistance to heavy or transition metal(loid)s but not for genes responsible for Se(IV) reduction.

Strain GZ436T was Gram-stain-negative, aerobic, non-motile, rod-shaped and isolated from the soil of a coal mine. 16S rRNA gene phylogenetic analysis showed that this strain clustered with Thermomonas brevis LMG 21746T (97.5 %), Thermomonas haemolytica A50-7-3T (96.3 %), Thermomonas koreensis KCTC 12540T (96.4 %), Thermomonas hydrothermalis SGM-6T (95.5 %) and Thermomonas fusca LMG 21737T (95.1 %). The major isoprenoid quinone was Q-8. The DNA G+C content was 67 mol%. Strain GZ436T contained phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, an unknown aminophospholipid, an unknown phospholipid and an unknown lipid as the major polar lipids. The predominant cellular fatty acids (>5 %) were iso-C15 : 0, iso-C11 : 0, iso-C11 : 0 3-OH, iso-C17 : 1ω9c, C16 : 0 and summed feature 3. The DNA–DNA relatedness value between strain GZ436T and T. brevis LMG 21746T was 54±0.4 %. According to phenotypic and phylogenetic characteristics, strain GZ436T represents a novel species of the genus Thermomonas , for which the name Thermomonas carbonis sp. nov. is proposed. The type strain is GZ436T ( = CCTCC AB 2013364T = KCTC 42013T).

A Gram-stain-positive, rod-shaped, facultatively anaerobic bacterium, designated strain ES3-24T, was isolated from a selenium mineral soil. The isolate was endospore-forming, nitrate-reducing and motile by means of peritrichous flagella. The major menaquinone was menaquinone 7 (MK-7) and the predominant fatty acids (>5 %) were anteiso-C15 : 0, iso-C16 : 0, C16 : 0 and anteiso-C17 : 0. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and two unknown aminophospholipids. Strain ES3-24T contained meso-diaminopimelic acid in the cell-wall peptidoglycan and the DNA G+C content was 49.6 mol%. According to phylogenetic analysis based on the 16S rRNA gene sequence, strain ES3-24T was most closely related to Paenibacillus terrigena A35T, with 16S rRNA gene sequence identity of 98.3 %, while the other members of the genus Paenibacillus had 16S rRNA gene sequence identities of less than 95.0 %. DNA–DNA relatedness between strain ES3-24T and P. terrigena CCTCC AB206026T was 39.3 %. In addition, strain ES3-24T showed obvious differences from closely related species in major polar lipids, nitrate reduction and other physiological and biochemical characteristics. The data from our polyphasic taxonomic study reveal that strain ES3-24T represents a novel species of the genus Paenibacillus , for which the name Paenibacillus selenitireducens sp. nov. is proposed. The type strain is ES3-24T ( = KCTC 33157T = CCTCC AB2013097T).

A Gram-reaction-negative, facultatively anaerobic, non-motile, rod-shaped, non-photosynthetic bacterial strain, DW2-9T, was isolated from soil. The highest 16S rRNA gene sequence similarities were found to Rhodobacter capsulatus ATCC 11166T (97.1 %), Rhodobacter viridis JA737T (96.4 %), Rhodobacter maris JA276T (96.2 %), Rhodobacter veldkampii ATCC 35703T (96.0 %), Haematobacter massiliensis CCUG 47968T (96.0 %), Haematobacter missouriensis CCUG 52307T (95.9 %) and Rhodobacter aestuarii JA296T (95.7 %). The genomic DNA G+C content was 67.2 mol% and the major respiratory quinone was ubiquinone 10 (Q-10). The major cellular fatty acids (>5 %) were C18 : 1ω7c, C16 : 0, C19 : 0 cyclo ω8c and summed feature 3 (one or more of iso-C15 : 0 2-OH, C16 : 1ω6c and C16 : 1ω7c). However, unlike species of the genus Rhodobacter , strain DW2-9T neither formed internal photosynthetic membranes nor produced photosynthetic pigments. DNA–DNA hybridization between strain DW2-9T and R. capsulatus JCM 21090T showed a relatedness of 33 %. Strain DW2-9T contained phosphatidylethanolamine, phosphatidylglycerol and an unknown aminophospholipid as major polar lipids, which differed from those of species of the genera Rhodobacter and Haematobacter . In addition to the differences in phylogenetic position and polar lipid types, strain DW2-9T could be distinguished from species of the genus Haematobacter by the cultivation conditions. On the basis of our polyphasic taxonomic analysis, strain DW2-9T is considered to represent a novel genus and species, for which the name Paenirhodobacter enshiensis gen. nov., sp. nov. is proposed. The type strain of Paenirhodobacter enshiensis is DW2-9T ( = CCTCC AB 2011145T = KCTC 15169T). Emended descriptions of the genera Rhodobacter and Haematobacter are also proposed.

A Gram-stain-positive, aerobic, motile, rod-shaped bacterium, designated strain Mn1-7T, was isolated from manganese mining soil in Tianjin, China. The closest phylogenetic relatives were Lysinibacillus massiliensis CCUG 49529T (97.2 % 16S rRNA gene sequence similarity), L. xylanilyticus XDB9T (96.7 %), L. sinduriensis JCM 15800T (96.2 %), L. odysseyi NBRC 100172T (95.9 %) and L. boronitolerans NBRC 103108T (95.4 %) (the type species of the genus). DNA–DNA hybridization values for strain Mn1-7T with the type strains of L. massiliensis and L. sinduriensis were 24.9 and 27.7 %, respectively. The genomic DNA G+C content was 38.4 mol%. The major menaquinone was MK-7 and the major fatty acids were iso-C15 : 0, iso-C16 : 0 and iso-C14 : 0. The major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The cell-wall peptidoglycan was type A4α (l-Lys–d-Asp), and the predominant cell-wall sugar was xylose. DNA–DNA hybridization results and comparison of phenotypic and chemotaxonomic characters between strain Mn1-7T and the phylogenetically most closely related strains revealed that the isolate represents a novel species of the genus Lysinibacillus , for which the name Lysinibacillus manganicus sp. nov. is proposed. The type strain is Mn1-7T ( = DSM 26584T = CCTCC AB 2012916T).

This work investigated the toxicity of two isomeric alkylphthalates, i.e. , di- n -octyl phthalate (DOP) and di-2-ethylhexyl phthalate (DEHP) to two model bacteria, Escherichia coli ( E. coli ) and Bacillus subtilis ( B. subtilis ), which have been previously used to study the toxicity of environmental pollutants. Microcalorimetry was used as the key analytical tool alongside scanning electron microscopy (SEM) and traditional microbiology techniques. The thermokinetic parameters from microcalorimetry showed that the phthalates had a biphasic effect on the metabolic activities of the bacteria; serving as energy sources for the bacteria thereby stimulating their growth at low dosages (≤150 μg/mL), but displaying inhibitory effects at higher dosages (≥300 μg/mL), indicated by a sharp decrease in growth rate constants at 450 μg/mL. The SEM revealed that the bacterial cells were morphological deformed, with shrunk cells and elongated strands at 600 μg/mL of both phthalates. The elongated strands inferred that the phthalates inhibited the reproductive processes of the bacteria by possibly impeding some stages of cell division. The half inhibitory concentrations of the phthalates showed that DEHP was more toxic than DOP. Additionally, E. coli , a facultative anaerobe, was more susceptible to the toxic effects of phthalates than B. subtilis , an obligate aerobe capable of forming endospores crucial for tolerating extreme environmental conditions.