A Combination of Genomics, Transcriptomics, and Genetics Provides Insights into the Mineral Weathering Phenotype of Pseudomonas azotoformans F77.

Silicate mineral weathering (dissolution) plays important roles in soil formation and global biogeochemical cycling. In this study, a combination of genomics, transcriptomics, and genetics was used to identify the molecular basis of mineral weathering activity and acid tolerance in Pseudomonas azotoformans F77. Biotite was chosen as a silicate mineral to investigate mineral weathering. The genome of strain F77 was sequenced, and the genes significantly upregulated when grown in the presence of biotite included mineral weathering-related genes associated with gluconic acid metabolism, flagellar assembly, and pilus biosynthesis and acid tolerance-related genes associated with neutralizing component production, reducing power, and proton efflux. The biotite-weathering behaviors of strain F77 and its mutants that were created by deleting the tkt, tal, and gntP genes, which are involved in gluconic acid metabolism, and the potF, nuoF, and gdtO genes, which are involved in acid tolerance, were determined. The Fe and Al concentrations in the strain F77-inoculated medium increased 2.2- to 13.7-fold compared to the controls. The cell numbers of strain F77 increased over time, while the pH values in the medium ranged from 3.75 to 3.90 between 20 and 36 h of incubation. The release of Al and Fe was significantly reduced in the F77 Δtal, F77 ΔgntP, F77 ΔpotF, and F77 ΔnuoF mutants. Bacterial growth was significantly reduced in the presence of biotite in the F77 ΔpotF and F77 ΔnuoF mutants. Our results demonstrated the acid tolerance of strain F77 and suggested that multiple genes and metabolic pathways in strain F77 are involved in biotite weathering and acid tolerance during the mineral weathering process. IMPORTANCE Acid production and tolerance play important roles in effective and persistent mineral weathering in bacteria, although the molecular mechanisms governing acid production and acid tolerance in bacteria have not been fully elucidated. In this study, the molecular mechanisms underlying biotite (as a silicate mineral) weathering (dissolution) and acid tolerance of P. azotoformans F77 were characterized using genomics, transcriptomics, and genetics analyses. Our results showed that the genes and metabolic pathways for gluconic acid metabolism, flagellar assembly, and pilus biosynthesis may play important roles in mineral weathering by strain F77. Notably, the genes associated with neutralizing component production, reducing power, and proton efflux may be related to acid tolerance in strain F77. The expression of these acid production- and acid tolerance-related genes was observed to be increased by biotite in strain F77. Our findings may help to elucidate the molecular mechanisms governing mineral weathering and, especially, acid tolerance in mineral-weathering bacteria.

Interactions between Biotite and the Mineral-Weathering Bacterium Pseudomonas azotoformans F77.

In this study, the mineral-weathering bacterium Pseudomonas azotoformans F77, which was isolated from the soil of a debris flow area, was evaluated for its weathering activity under direct contact with biotite or without contact. Then, biotite-weathering behaviors of strain F77, mutants that had been created by deleting the gcd and adh genes (which are involved in gluconic acid metabolism and pilus formation, respectively), and the double mutant F77ΔgcdΔadh were compared. The relative gene expression levels of F77 and its mutants F77Δgcd and F77Δadh were also analyzed in the presence of biotite. Direct contact with biotite increased Fe and Al release from the mineral in the presence of F77. All strains had similar abilities to release Fe and Al from the mineral except for F77Δgcd and F77Δadh Mobilized Fe and Al concentrations were decreased by up to 72, 26, and 87% in the presence of F77Δgcd, F77Δadh, and F77ΔgcdΔadh, respectively, compared to levels observed in the presence of F77 during the mineral-weathering process. Gluconic acid production was decreased for F77Δgcd and F77ΔgcdΔadh, while decreased cell attachment on the mineral surface was observed for F77Δadh, compared to findings for F77. The F77 genes involved in pilus formation and gluconic acid metabolism showed increased expression levels in the presence of biotite. The results of this study showed important roles for the genes involved in gluconic acid metabolism and pilus formation in mineral weathering by F77 and demonstrated the distinctive effect of these genes on mineral weathering by F77.IMPORTANCE Bacteria play important roles in mineral weathering and soil formation, although the molecular mechanisms underlying the interactions between bacteria and silicate minerals are poorly understood. In this study, the interactions between biotite and the highly effective mineral-weathering bacterium P. azotoformans F77 were characterized. Our results showed that the genes involved in gluconic acid metabolism and pilus formation play important roles in mineral weathering by F77. The presence of biotite could promote the expression of these genes in F77, and a distinctive effect of these genes on mineral weathering by F77 was observed in this study. Our results provide new knowledge and promote better understanding regarding the interaction between silicate minerals and mineral-weathering bacteria, as well as the molecular mechanisms involved in these processes.

Increased biomass and quality and reduced heavy metal accumulation of edible tissues of vegetables in the presence of Cd-tolerant and immobilizing Bacillus megaterium H3.

A Cd-resistant and immobilizing Bacillus megaterium H3 was characterized for its impact on the biomass and quality and heavy metal uptake of edible tissues of two vegetables (Brassica campestris L. var. Aijiaohuang and Brassica rapa L. var. Shanghaiqing) grown in heavy metal-polluted soil. The impact of strain H3 on the soil quality was also evaluated. The increase in the edible tissue biomass and the contents of soluble proteins and vitamin C of the vegetables inoculated with strain H3 ranged from 18% to 33%, 17% to 31%, and 15% to 19%, respectively, compared with the controls. Strain H3 significantly decreased the edible tissue Cd and Pb contents of the two greens (41-80%), DTPA-extractable Cd content (35-47%) of the rhizosphere soils, and Cd and Pb translocation factors (25-56%) of the greens compared with the controls. Moreover, strain H3 significantly increased the organic matter content (17-21%) and invertase activity (13-14%) of the rhizosphere soils compared with the controls. Our results demonstrated the increased edible tissue biomass and quality, decreased Cd and Pb uptake of the edible tissues, and improved soil quality in the presence of strain H3. The results also suggested an effective bacterial-enhanced technique for decreased metal uptake of greens and improved vegetable and soil qualities in the metal-contaminated soils.

Isolation and characterization of mineral-dissolving bacteria from different levels of altered mica schist surfaces and the adjacent soil.

Microorganisms play important role in mineral weathering. However, little is known about rock-associated mineral-dissolving bacteria. In this study, 129 bacterial isolates were obtained from the less and more weathered mica schist surfaces and the adjacent soil and characterized for mineral dissolving activity, population, and the linkage of rock weathering level and distribution of the bacteria. Among the 129 isolates, 112 isolates could dissolve biotite. The relative abundance of the highly effective Fe solubilizers was significantly higher on the more altered rock surface (89.6%) than in the soil (51.2%) and on the less altered rock surface (22.5%), while the relative abundance of the highly effective Si solubilizers was significantly higher in the soil (65.9%) than on the more (41.7%) and less (12.5%) altered rock surfaces. Furthermore, 17.5-42.5%, 87.5%, and 60.9-90.2% of the highly effective acid- and siderophore-producing isolates were obtained in the less and more weathered rocks and the soil, respectively. The mineral-dissolving bacteria belonged to 18 genera and Burkholderia, Bacillus, and Paenibacillus were the dominant and highly effective mineral-dissolving bacteria. Phylogenetic analysis found 2, 9, and 5 bacterial species in the highly effective mineral-dissolving bacteria on the less and more altered rock surfaces and in the soil, respectively. The results showed the abundant and diverse mineral-dissolving bacterial populations on the more weathered rock surfaces. The results also suggested distinct mineral-dissolving activities and mechanisms of the bacteria and highlighted the possibility for the development of bacterial inocula for plant nutrition improvement in silicate mineral-rich soils.

Cd immobilization and reduced tissue Cd accumulation of rice (Oryza sativa wuyun-23) in the presence of heavy metal-resistant bacteria.

Two metal-resistant Bacillus megaterium H3 and Neorhizobium huautlense T1-17 were investigated for their immobilization of Cd in solution and tissue Cd accumulation of rice (Oryza sativa wuyun-23) in the Cd-contaminated soil. Strains H3 and T1-17 decreased 79-96% of water-soluble Cd in solution and increased grain biomass in the high Cd-contaminated soil. Inoculation with H3 and T1-17 significantly decreased the root (ranging from 25% to 58%), above-ground tissue (ranging from 13% to 34%), and polished rice (ranging from 45% to 72%) Cd contents as well as Cd bioconcentration factor of the rice compared to the controls. Furthermore, H3 and T1-17 significantly reduced the exchangeable Cd content of the rhizosphere soils compared with the controls. Notably, strain T1-17 had significantly higher ability to reduce Cd bioconcentration factor and polished rice Cd uptake than strain H3. The results demonstrated that H3 and T1-17 decreased the tissue (especially polished rice) Cd uptake by decreasing Cd availability in soil and Cd bioconcentration factor and the effect on the reduced polished rice Cd uptake was dependent on the strains. The results may provide an effective synergistic bioremediation of Cd-contaminated soils in the bacteria and rice plants and bacterial-assisted safe production of rice in Cd-contaminated soils.

Distinct Mineral Weathering Behaviors of the Novel Mineral-Weathering Strains Rhizobium yantingense H66 and Rhizobium etli CFN42.

UNLABELLED: Bacteria play important roles in mineral weathering, soil formation, and element cycling. However, little is known about the interaction between silicate minerals and rhizobia. In this study, Rhizobium yantingense H66 (a novel mineral-weathering rhizobium) and Rhizobium etli CFN42 were compared with respect to potash feldspar weathering, mineral surface adsorption, and metabolic activity during the mineral weathering process. Strain H66 showed significantly higher Si, Al, and K mobilization from the mineral and higher ratios of cell numbers on the mineral surface to total cell numbers than strain CFN42. Although the two strains produced gluconic acid, strain H66 also produced acetic, malic, and succinic acids during mineral weathering in low- and high-glucose media. Notably, higher Si, Al, and K releases, higher ratios of cell numbers on the mineral surface to total cell numbers, and a higher production of organic acids by strain H66 were observed in the low-glucose medium than in the high-glucose medium. Scanning electron microscope analyses of the mineral surfaces and redundancy analysis showed stronger positive correlations between the mineral surface cell adsorption and mineral weathering, indicated by the dissolved Al and K concentrations. The results showed that the two rhizobia behaved differently with respect to mineral weathering. The results suggested that Rhizobium yantingense H66 promoted potash feldspar weathering through increased adsorption of cells to the mineral surface and through differences in glucose metabolism at low and high nutrient concentrations, especially at low nutrient concentrations. IMPORTANCE: This study reported the potash feldspar weathering, the cell adsorption capacity of the mineral surfaces, and the metabolic differences between the novel mineral-weathering Rhizobium yantingense H66 and Rhizobium etli CFN42 under different nutritional conditions. The results showed that Rhizobium yantingense H66 had a greater ability to weather the mineral in low- and high-glucose media, especially in the low-glucose medium. Furthermore, Rhizobium yantingense H66 promoted mineral weathering through the increased adsorption of cells to the mineral surface and through increased organic acid production. Our results allow us to better comprehend the roles of different rhizobia in silicate mineral weathering, element cycling, and soil formation in various soil environments, providing more insight into the geomicrobial contributions of rhizobia to these processes.

Saccharibacillus qingshengii sp. nov., isolated from a lead-cadmium tailing.

A Gram-stain-positive, strictly aerobic strain, H6T, was isolated from a soil sample of lead-cadmium tailing in Qixia district, Nanjing (China). Cells of the strain are rod-shaped and colonies on LB agar are red. Strain H6T has subpolar and polar flagella and the optimal condition for growth is 30 °C, with 1 % (w/v) NaCl and at pH 7.0. Based on the 16S rRNA gene sequences, phylogenetic analysis showed that strain H6T was closely related to the genus Saccharibacillus, and the closest relatives were Saccharibacillus deserti WLJ055T (99.0 % 16S rRNA gene sequence similarity), Saccharibacillus kuerlensis HR1T (97.0 %) and Saccharibacillus sacchari GR21T (96.4 %). The DNA-DNA relatedness value between strain H6T and S. deserti WLJ055T was 55.0 %. The major polar lipids of strain H6T were diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid and three unknown glycolipids. The DNA G+C content was 58.4 mol% and MK-7 was the major isoprenoid quinone. The major fatty acids were anteiso-C15 : 0 and C16 : 0. meso-Diaminopimelic acid was detected in the peptidoglycan. Based on the phylogenetic, biochemical and chemotaxonomic data, strain H6T represents a novel species of the genus Saccharibacillus, for which the name Saccharibacillus qingshengii sp. nov., is proposed. The type strain is H6T (=CCTCC AB 2016001T=JCM 31172T).

Increased growth and root Cu accumulation of Sorghum sudanense by endophytic Enterobacter sp. K3-2: Implications for Sorghum sudanense biomass production and phytostabilization.

Endophytic bacterial strain K3-2 was isolated from the roots of Sorghum sudanense (an bioenergy plant) grown in a Cu mine wasteland soils and characterized. Strain K3-2 was identified as Enterobacter sp. based on 16S rRNA gene sequence analysis. Strain K3-2 exhibited Cu resistance and produced 1-aminocyclopropane-1-carboxylate (ACC) deaminase, indole-3-acetic acid (IAA), siderophores, and arginine decarboxylase. Pot experiments showed that strain K3-2 significantly increased the dry weight and root Cu accumulation of Sorghum sudanense grown in the Cu mine wasteland soils. Furthermore, increase in total Cu uptake (ranging from 49% to 95%) of the bacterial inoculated-Sorghum sudanense was observed compared to the control. Notably, most of Cu (83-86%) was accumulated in the roots of Sorghum sudanense. Furthermore, inoculation with strain K3-2 was found to significantly increase Cu bioconcentration factors and the proportions of IAA- and siderophore-producing bacteria in the root interiors and rhizosphere soils of Sorghum sudanense compared with the control. Significant decrease in the available Cu content was also observed in the rhizosphere soils of the bacterial-inoculated Sorghum sudanense. The results suggest that the endophytic bacterial strain K3-2 may be exploited for promoting Sorghum sudanense biomass production and Cu phytostabilization in the Cu mining wasteland soils.

Rhizobium yantingense sp. nov., a mineral-weathering bacterium.

A Gram-stain-negative, rod-shaped bacterial strain, H66(T), was isolated from the surfaces of weathered rock (purple siltstone) found in Yanting, Sichuan Province, PR China. Cells of strain H66(T) were motile with peritrichous flagella. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain H66(T) belongs to the genus Rhizobium. It is closely related to Rhizobium huautlense SO2(T) (98.1 %), Rhizobium alkalisoli CCBAU 01393(T) (98.0 %) and Rhizobium cellulosilyticum ALA10B2(T) (98.0 %). Analysis of the housekeeping genes, recA, glnII and atpD, showed low levels of sequence similarity (<92.0 %) between strain H66(T) and other recognized species of the genus Rhizobium. The predominant components of the cellular fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0. The G+C content of strain H66(T) was 60.3 mol%. Strain H66(T) is suggested to be a novel species of the genus Rhizobium based on the low levels of DNA-DNA relatedness (ranging from 14.3 % to 40.0 %) with type strains of species of the genus Rhizobium and on its unique phenotypic characteristics. The namehttp://dx.doi.org/10.1601/nm.1279Rhizobium yantingense sp. nov. is proposed for this novel species. The type strain is H66(T) ( = CCTCC AB 2014007(T) = LMG 28229(T)).

Chitinophaga longshanensis sp. nov., a mineral-weathering bacterium isolated from weathered rock.

A Gram-stain-negative, aerobic, yellow-pigmented, non-motile, non-spore-forming, rod-shaped bacterial strain, Z29(T), was isolated from the surface of weathered rock (potassic trachyte) from Nanjing, Jiangsu Province, PR China. Phylogenetic analysis based on 16S rRNA gene sequences suggested that strain Z29(T) belongs to the genus Chitinophaga in the family Chitinophagaceae. Levels of 16S rRNA gene sequence similarity between strain Z29(T) and the type strains of recognized species of the genus Chitinophaga ranged from 92.7 to 98.2 %. The main fatty acids of strain Z29(T) were iso-C15 : 0, C16 : 1ω5c and iso-C17 : 0 3-OH. It also contained menaquinone 7 (MK-7) as the respiratory quinone and homospermidine as the main polyamine. The polar lipid profile contained phosphatidylethanolamine, unknown aminolipids, unknown phospholipids and unknown lipids. The total DNA G+C content of strain Z29(T) was 51.3 mol%. Phenotypic properties and chemotaxonomic data supported the affiliation of strain Z29(T) with the genus Chitinophaga. The low level of DNA-DNA relatedness (ranging from 14.6 to 29.8 %) to the type strains of other species of the genus Chitinophaga and differential phenotypic properties demonstrated that strain Z29(T) represents a novel species of the genus Chitinophaga, for which the name Chitinophaga longshanensis sp. nov. is proposed. The type strain is Z29(T) ( = CCTCC AB 2014066(T) = LMG 28237(T)).

Chitinophaga qingshengii sp. nov., isolated from weathered rock surface.

A novel mineral-weathering bacterium was isolated from weathered rock (potassic trachyte) surfaces collected from Nanjing (Jiangsu, PR China). Cells of strain JN246(T) were Gram-stain-negative, rod-shaped and non-motile. Strain JN246(T) was aerobic, catalase- and oxidase-positive, and grew optimally at 28 °C and pH 7.0. On the basis of 16S rRNA gene sequence analysis, strain JN246(T) belonged to the genus Chitinophaga and the closest phylogenetic relatives were Chitinophaga eiseniae YC6729(T) (98.5% 16S rRNA gene sequence similarity), Chitinophaga terrae KP01(T) (96.8%), and Chitinophaga jiangningensis JN53(T) (96.3 %). The major respiratory quinone was MK-7 and the major polyamine was homospermidine. The major fatty acids were iso-C15:0, C16:1ω5c, C16:0 and iso-C17:0 3-OH. The polar lipid profile of strain JN246(T) consisted of phosphatidylethanolamine, unknown aminolipids and unknown lipids. The genomic DNA G+C content of strain JN246(T) was 48.8 mol%. Based on the low level of DNA-DNA relatedness of strain JN246(T) (ranging from 22.6% to 42.4%) to the type strains of other species of the genus Chitinophaga and unique phenotypic characteristics, strain JN246(T) represents a novel species of the genus Chitinophaga, for which the name Chitinophaga qingshengii sp. nov. is proposed. The type strain is JN246(T) ( = CCTCC AB 2014201(T) = JCM 30026(T)).

Arthrobacter nanjingensis sp. nov., a mineral-weathering bacterium isolated from forest soil.

A Gram-stain-positive, non-motile, rod- or coccoid-shaped actinobacterium, designated strain A33(T), was isolated from a forest soil sample from Nanjing, Jiangsu Province, PR China. The strain grew optimally at 30 °C, pH 7.0 and with 3 % NaCl (w/v). Phylogenetic analysis of the strain, based on 16S rRNA gene sequences, showed that it was most closely related to Arthrobacter woluwensis (98.4 % sequence similarity), Arthrobacter humicola (97.5 %), Arthrobacter globiformis (97.4 %), Arthrobacter oryzae (97.3 %) and Arthrobacter cupressi (97.0 %). The major cellular fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C15 : 0; MK-9(H2) was the predominant respiratory quinone. The polar lipids comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and three glycolipids. Cell-wall analysis revealed that the peptidoglycan type was A3α, based on l-lysine-l-alanine; the cell-wall sugars were galactose and mannose. The genomic G+C content of strain A33(T) was 66.8 mol%. The low DNA-DNA relatedness values between strain A33(T) and recognized species of the genus Arthrobacter and many phenotypic properties supported the classification of strain A33(T) as a representative of a novel species of the genus Arthrobacter, for which the name Arthrobacter nanjingensis sp. nov. is proposed. The type strain is A33(T) ( = CCTCC AB 2014069(T) = DSM 28237(T)).

Sinomonas susongensis sp. nov., isolated from the surface of weathered biotite.

A novel actinomycete, designated strain A31(T), was isolated from the surface of weathered biotite in Susong, Anhui Province, China. The organism grew optimally at 30 °C, at pH 8.0 and with 1% (w/v) NaCl. Strain A31(T) had A3α as the cell-wall peptidoglycan type and galactose, mannose and rhamnose as whole-cell sugars. Anteiso-C(15 : 0) and anteiso-C(17 : 0) were the major cellular fatty acids and MK-9(H2) was the predominant respiratory quinone. In addition, the total polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylmonomethylethanolamine and four glycolipids. The genomic DNA G+C content of strain A31(T) was 70.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain A31(T) was related most closely to Sinomonas albida LC13(T) (98.3% similarity), Sinomonas atrocyanea DSM 20127(T) (98.2%), Sinomonas soli CW 59(T) (98.1%), Sinomonas flava CW 108(T) (97.8%), 'Sinomonas mesophila' MPKL 26 (97.3%), Sinomonas echigonensis LC10(T) (97.1%) and ' Sinomonas notoginsengisoli ' SYP-B575 (96.7%). DNA-DNA hybridization studies with the new isolate showed relatedness values of 16.0-56.6% with its six closest neighbours. Based on phenotypic, chemotaxonomic and phylogenetic analysis, strain A31(T) represents a novel species of the genus Sinomonas , for which the name Sinomonas susongensis sp. nov. is proposed. The type strain is A31(T) ( = DSM 28245(T) = CCTCC AB 2014068(T)).

Burkholderia susongensis sp. nov., a mineral-weathering bacterium isolated from weathered rock surface.

A novel type of mineral-weathering bacterium was isolated from the weathered surface of rock (mica schist) collected from Susong (Anhui, China). Cells of strain L226(T) were Gram-stain-negative. The strain grew optimally at 30 °C, with 1 % (w/v) NaCl and at pH 7.0 in trypticase soy broth. On the basis of 16S rRNA gene phylogeny, strain L226(T) was shown to belong to the genus Burkholderia and the closest phylogenetic relatives were Burkholderia sprentiae WSM5005(T) (98.3 %), Burkholderia acidipaludis NBRC 101816(T) (98.2 %), Burkholderia tuberum STM678(T) (97.2 %) and Burkholderia diazotrophica JPY461(T) (97.1 %). The DNA G+C content was 63.5 mol% and the respiratory quinone was Q-8. The major fatty acids were C16 : 0, C17 : 0 cyclo and C19 : 0 cyclo ω8c. The polar lipid profile of strain L226(T) consisted of a mixture of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, unknown lipids and unidentified aminophospholipids. Based on the low level of DNA-DNA relatedness (ranging from 25.8 % to 34.4 %) to the tested type strains of species of the genus Burkholderia and unique phenotypic characteristics, it is suggested that strain L226(T) represents a novel species of the genus Burkholderia, for which the name Burkholderia susongensis sp. nov., is proposed. The type strain is L226(T) ( = CCTCC AB2014142(T) = JCM 30231(T)).

Characterization of Mn-resistant endophytic bacteria from Mn-hyperaccumulator Phytolacca americana and their impact on Mn accumulation of hybrid penisetum.

Three hundred Mn-resistant endophytic bacteria were isolated from the Mn-hyperaccumulator, Phytolacca americana, grown at different levels of Mn (0, 1, and 10mM) stress. Under no Mn stress, 90%, 92%, and 11% of the bacteria produced indole acetic acid (IAA), siderophore, and 1-aminocyclopropane-1-carboxylate (ACC) deaminase, respectively. Under Mn stress, 68-94%, 91-92%, and 21-81% of the bacteria produced IAA, siderophore, and ACC deaminase, respectively. Greater percentages of ACC deaminase-producing bacteria were found in the Mn-treated P. americana. Furthermore, the ratios of IAA- and siderophore-producing bacteria were significantly higher in the Mn treated plant leaves, while the ratio of ACC deaminase-producing bacteria was significantly higher in the Mn treated-roots. Based on 16S rRNA gene sequence analysis, Mn-resistant bacteria were affiliated with 10 genera. In experiments involving hybrid penisetum grown in soils treated with 0 and 1000mgkg(-1) of Mn, inoculation with strain 1Y31 was found to increase the root (ranging from 6.4% to 18.3%) and above-ground tissue (ranging from 19.3% to 70.2%) mass and total Mn uptake of above-ground tissues (64%) compared to the control. Furthermore, inoculation with strain 1Y31 was found to increase the ratio of IAA-producing bacteria in the rhizosphere and bulk soils of hybrid penisetum grown in Mn-added soils. The results showed the effect of Mn stress on the ratio of the plant growth-promoting factor-producing endophytic bacteria of P. americana and highlighted the potential of endophytic bacterium as an inoculum for enhanced phytoremediation of Mn-polluted soils by hybrid penisetum plants.

Isolation and the interaction between a mineral-weathering Rhizobium tropici Q34 and silicate minerals.

The purposes of this study were to isolate and evaluate the interaction between mineral-weathering bacteria and silicate minerals (feldspar and biotite). A mineral-weathering bacterium was isolated from weathered rocks and identified as Rhizobium tropici Q34 based on 16S rRNA gene sequence analysis. Si and K concentrations were increased by 1.3- to 4.0-fold and 1.1- to 1.7-fold in the live bacterium-inoculated cultures compared with the controls respectively. Significant increases in the productions of tartaric and succinic acids and extracellular polysaccharides by strain Q34 were observed in cultures with minerals. Furthermore, significantly more tartaric acid and polysaccharide productions by strain Q34 were obtained in the presence of feldspar, while better growth and more citric acid production of strain Q34 were observed in the presence of biotite. Mineral dissolution experiments showed that the organic acids and polysaccharides produced by strain Q34 were also capable of promoting the release of Si and K from the minerals. The results showed that the growth and metabolite production of strain Q34 were enhanced in the presence of the minerals and different mineral exerted distinct impacts on the growth and metabolite production. The bio-weathering process is probably a synergistic action of organic acids and extracellular polysaccharides produced by the bacterium.

Depth-related changes in community structure of culturable mineral weathering bacteria and in weathering patterns caused by them along two contrasting soil profiles.

Bacteria play important roles in mineral weathering and soil formation. However, few reports of mineral weathering bacteria inhabiting subsurfaces of soil profiles have been published, raising the question of whether the subsurface weathering bacteria are fundamentally distinct from those in surface communities. To address this question, we isolated and characterized mineral weathering bacteria from two contrasting soil profiles with respect to their role in the weathering pattern evolution, their place in the community structure, and their depth-related changes in these two soil profiles. The effectiveness and pattern of bacterial mineral weathering were different in the two profiles and among the horizons within the respective profiles. The abundance of highly effective mineral weathering bacteria in the Changshu profile was significantly greater in the deepest horizon than in the upper horizons, whereas in the Yanting profile it was significantly greater in the upper horizons than in the deeper horizons. Most of the mineral weathering bacteria from the upper horizons of the Changshu profile and from the deeper horizons of the Yanting profile significantly acidified the culture media in the mineral weathering process. The proportion of siderophore-producing bacteria in the Changshu profile was similar in all horizons except in the Bg2 horizon, whereas the proportion of siderophore-producing bacteria in the Yanting profile was higher in the upper horizons than in the deeper horizons. Both profiles existed in different highly depth-specific culturable mineral weathering community structures. The depth-related changes in culturable weathering communities were primarily attributable to minor bacterial groups rather than to a change in the major population structure.

Myroides xuanwuensis sp. nov., a mineral-weathering bacterium isolated from forest soil.

A Gram-reaction-negative, aerobic, non-motile, yellow-pigmented, rod-shaped bacterium, designated strain TH-19(T), was isolated from a forest soil sample in Jiangsu province, China. On the basis of 16S rRNA gene sequence similarity, strain TH-19(T) was shown to belong to the genus Myroides, a member of the phylum Bacteroidetes, and was related to Myroides odoratimimus LMG 4029(T) (98.7% similarity), Myroides profundi D25(T) (98.2%) and Myroides marinus JS-08(T) (97.5%). Strain TH-19(T) contained menaquinone-6 (MK-6) as the predominant menaquinone, and the dominant fatty acids were iso-C(15 : 0) and iso-C(17 : 0) 3-OH. The DNA G+C content of strain TH-19(T) was 37.2 mol%. The DNA-DNA relatedness values of strain TH-19(T) with Myroides odoratimimus JCM 7460(T), Myroides profundi D25(T) and Myroides marinus JS-08(T) were below 70%. Based on phenotypic, genotypic and phylogenetic evidence, it is suggested that strain TH-19(T) represents a novel species of the genus Myroides, for which the name Myroides xuanwuensis sp. nov. is proposed. The type strain is TH-19(T) ( = CCTCC AB 2013145(T) = JCM 19200(T)).

Chitinophaga jiangningensis sp. nov., a mineral-weathering bacterium.

A Gram-stain-negative, rod-shaped bacterial strain, JN53(T), was isolated from the surfaces of weathered rock (potassic trachyte) from Nanjing, Jiangsu Province, PR China. Strain JN53(T) grew optimally at 30 °C, pH 7.0. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain JN53(T) belonged to the genus Chitinophaga in the family Chitinophagaceae. It was most closely related to Chitinophaga terrae KP01(T) (97.3 % 16S rRNA gene sequence similarity), Chitinophaga eiseniae YC6729(T) (96.3 %). Strain JN53(T) contained MK-7 as the major menaquinone and homospermidine as the major polyamine. The main fatty acids of strain JN53(T) were iso-C15 : 0, C16 : 1ω5c, C16 : 1ω7c and/or C16 : 1ω6c (summed feature 3), iso-C17 : 0 3-OH, C16 : 0, iso-C15 : 0 3-OH and C16 : 0 3-OH. The polar lipid profile contained phosphatidylethanolamine, unknown aminolipids and unknown lipids. The total DNA G+C content of strain JN53(T) was 49.7 mol%. The low level of DNA-DNA relatedness to other species of the genus Chitinophaga and the many phenotypic properties that distinguished strain JN53(T) from recognized species of this genus demonstrated that isolate JN53(T) should be classified as representing a novel species of the genus Chitinophaga, for which the name Chitinophaga jiangningensis sp. nov. is proposed. The type strain is JN53(T) ( = CCTCC AB 2013166(T) = JCM 19354(T)).

Bacillus qingshengii sp. nov., a rock-weathering bacterium isolated from weathered rock surface.

A novel type of rock-weathering bacterium was isolated from weathered rock (tuff) surface collected from Dongxiang (Jiangxi, eastern China). Cells of strain G19(T) were Gram-reaction-positive, rod-shaped, endospore-forming and non-motile. The strain was aerobic, catalase- and oxidase-positive, and grew optimally at 30 °C and pH 7.0. On the basis of 16S rRNA gene sequence analysis, strain G19(T) was shown to belong to the genus Bacillus and the closest phylogenetic relatives were Bacillus aryabhattai B8W22(T) (97.4%) and Bacillus megaterium IAM 13418(T) (97.1%). The DNA G+C content was 36.7 mol% and the predominant respiratory quinone was MK-7. The major fatty acids were iso-C14 : 0, iso-C15 : 0 and anteiso-C15 : 0. The polar lipid profile of strain G19(T) contained phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and an unidentified lipid. Based on the low level of DNA-DNA relatedness (ranging from 49.4% to 55.0%) to these type strains of species of the genus Bacillus and unique phenotypic characteristics, strain G19(T) represents a novel species of the genus Bacillus, for which the name Bacillus qingshengii sp. nov. is proposed. The type strain is G19(T) ( = CCTCC AB 2013273(T) = JCM 19454(T)).