A strain secreting a strongly acidic polysaccharide flocculating agent was isolated from activated sludge, and identified as Bacillus brevis. The bioflocculant was produced by RL-2 during the late logarithmic growth i...A strain secreting a strongly acidic polysaccharide flocculating agent was isolated from activated sludge, and identified as Bacillus brevis. The bioflocculant was produced by RL-2 during the late logarithmic growth in the batch culture and was recovered from supernatant by ethanol precipitation. The bioflocculant is thermo-stable as its activity remains stable after heated at 100 °C for 45 min. Its flocculating activity with kaolin suspensions was stimulated by the addition of Ca2+, Al3+ and Cu2+. The flocculant consists of glucose, mannose, and galacturonic acid. Its average molecular mass was estimated to be approximately 2.86×105 by the method of viscosity. The flocculant aggregates various inorganic and organic compounds in solution.展开更多
The microbial reduction of U（VI） by Bacillus sp. dwc-2, isolated from soil in Southwest China, was explored using transmission electron microscopy （TEIVI）, X-ray photoelectron spectros- copy （XPS） and X-ray abso...The microbial reduction of U（VI） by Bacillus sp. dwc-2, isolated from soil in Southwest China, was explored using transmission electron microscopy （TEIVI）, X-ray photoelectron spectros- copy （XPS） and X-ray absorption near edge spectroscopy （XANES）. Our studies indicated that approximately 16.0% of U（VI） at an initial concentration of 100 mg/L uranium nitrate could be reduced by Bacillus sp. dwc-2 at pH 8.2 under anaerobic conditions at room temperature. Additionally, natural organic matter （NOM） played an important role in enhancing the bioreduction of U（VI） by Bacillus sp. dwc-2. XPS results demonstrated that the uranium presented mixed valence states （U（VI） and U（IV）） after bioreduction, which was subse- quently confirmed by XANES. Furthermore, the TEM and high resolution transmission electron microscopy （HRTEM） analysis suggested that the reduced uranium was bioaccumulated mainly within the cell and as a crystalline structure on the cell wa11. These observations implied that the reduction of uranium may have a significant effect on its fate in the soil environment in which these bacterial strains occur.展开更多
To determine the impact of carbohydrates on the metabolic pathway in alkaliphiles, proteomes were obtained from cultures containing different carbohydrates and were resolved on two-dimensional gel electrophoresis (2-D...To determine the impact of carbohydrates on the metabolic pathway in alkaliphiles, proteomes were obtained from cultures containing different carbohydrates and were resolved on two-dimensional gel electrophoresis (2-DE). The proteomes were compared to determine differentially expressed proteins. A novel alkaliphilic bacterium (alkaliphilic Bacillus sp. N16-5 isolated from Wudunur Soda Lake, China) was isolated in media with five different carbon sources (glucose, mannose, galactose, arabinose, and xylose). Comparative proteome analysis identified 61 differentially expressed proteins, which were mainly involved in carbohydrate metabolism, amino acid transport, and metabolism, as well as energy production and conversion. The comparison was based on the draft genome sequence of strain N16-5. The abundance of enzymes involved in central metabolism was significantly changed when exposed to various carbohydrates. Notably, catabolite control protein A (CcpA) was up-regulated under all carbon sources compared with glucose. In addition, pentose exhibited a stronger effect than hexose in CcpA-mediated carbon catabolite repression. These results provided a fundamental understanding of carbohydrate metabolism in alkaliphiles.展开更多
The present study was aimed to assess the ability of Bacillus sp.JDM-2-1 and Staphylococcus capitis to reduce hexavalent chromium into its trivalent form.Bacillus sp.JDM-2-1 could tolerate Cr（Ⅵ）（4800 μg/mL） and ...The present study was aimed to assess the ability of Bacillus sp.JDM-2-1 and Staphylococcus capitis to reduce hexavalent chromium into its trivalent form.Bacillus sp.JDM-2-1 could tolerate Cr（Ⅵ）（4800 μg/mL） and S.capitis could tolerate Cr（Ⅵ）（2800 μg/mL）.Both organisms were able to resist Cd^2＋（50 μg/mL）,Cu^2＋（200 μg/mL）,Pb^2＋（800 μg/mL）,Hg^2＋（50 μg/mL） and Ni2＋（4000 μg/mL）.S.capitis resisted Zn^2＋ at 700 μg/mL while Bacillus sp.JDM-2-1 only showed resistance up to 50 μg/mL.Bacillus sp.JDM-2-1 and S.capitis showed optimum growth at pH 6 and 7,respectively,while both bacteria showed optimum growth at 37°C.Bacillus sp.JDM-2-1 and S.capitis could reduce 85% and 81% of hexavalent chromium from the medium after 96 h and were also capable of reducing hexavalent chromium 86% and 89%,respectively,from the industrial effuents after 144 h.Cell free extracts of Bacillus sp.JDM-2-1 and S.capitis showed reduction of 83% and 70% at concentration of 10 μg Cr（Ⅵ）/mL,respectively.The presence of an induced protein having molecular weight around 25 kDa in the presence of chromium points out a possible role of this protein in chromium reduction.The bacterial isolates can be exploited for the bioremediation of hexavalent chromium containing wastes,since they seem to have a potential to reduce the toxic hexavalent form to its nontoxic trivalent form.展开更多
文摘A strain secreting a strongly acidic polysaccharide flocculating agent was isolated from activated sludge, and identified as Bacillus brevis. The bioflocculant was produced by RL-2 during the late logarithmic growth in the batch culture and was recovered from supernatant by ethanol precipitation. The bioflocculant is thermo-stable as its activity remains stable after heated at 100 °C for 45 min. Its flocculating activity with kaolin suspensions was stimulated by the addition of Ca2+, Al3+ and Cu2+. The flocculant consists of glucose, mannose, and galacturonic acid. Its average molecular mass was estimated to be approximately 2.86×105 by the method of viscosity. The flocculant aggregates various inorganic and organic compounds in solution.
基金supported by the National Natural Science Foundation(Nos.21071102,91126013)Joint Funds of National Natural Science Foundation and China Academy of Engineering Physics(NSAF,No.U1330125)+1 种基金the National High Technology Research and Development Program(863)of China(No.2012AA063503)the National Fund of China for Fostering Talents in Basic Science(No.J1210004)
文摘The microbial reduction of U（VI） by Bacillus sp. dwc-2, isolated from soil in Southwest China, was explored using transmission electron microscopy （TEIVI）, X-ray photoelectron spectros- copy （XPS） and X-ray absorption near edge spectroscopy （XANES）. Our studies indicated that approximately 16.0% of U（VI） at an initial concentration of 100 mg/L uranium nitrate could be reduced by Bacillus sp. dwc-2 at pH 8.2 under anaerobic conditions at room temperature. Additionally, natural organic matter （NOM） played an important role in enhancing the bioreduction of U（VI） by Bacillus sp. dwc-2. XPS results demonstrated that the uranium presented mixed valence states （U（VI） and U（IV）） after bioreduction, which was subse- quently confirmed by XANES. Furthermore, the TEM and high resolution transmission electron microscopy （HRTEM） analysis suggested that the reduced uranium was bioaccumulated mainly within the cell and as a crystalline structure on the cell wa11. These observations implied that the reduction of uranium may have a significant effect on its fate in the soil environment in which these bacterial strains occur.
基金supported by the National Basic Research Program of China, Ministry of Science and Technology of China (Grant Nos. 2007CB707801 and 2003CB716001)the National High Technology Research and Development Program of China (Grant Nos. 2006AA020201 and 2007AA021306)
文摘To determine the impact of carbohydrates on the metabolic pathway in alkaliphiles, proteomes were obtained from cultures containing different carbohydrates and were resolved on two-dimensional gel electrophoresis (2-DE). The proteomes were compared to determine differentially expressed proteins. A novel alkaliphilic bacterium (alkaliphilic Bacillus sp. N16-5 isolated from Wudunur Soda Lake, China) was isolated in media with five different carbon sources (glucose, mannose, galactose, arabinose, and xylose). Comparative proteome analysis identified 61 differentially expressed proteins, which were mainly involved in carbohydrate metabolism, amino acid transport, and metabolism, as well as energy production and conversion. The comparison was based on the draft genome sequence of strain N16-5. The abundance of enzymes involved in central metabolism was significantly changed when exposed to various carbohydrates. Notably, catabolite control protein A (CcpA) was up-regulated under all carbon sources compared with glucose. In addition, pentose exhibited a stronger effect than hexose in CcpA-mediated carbon catabolite repression. These results provided a fundamental understanding of carbohydrate metabolism in alkaliphiles.
文摘The present study was aimed to assess the ability of Bacillus sp.JDM-2-1 and Staphylococcus capitis to reduce hexavalent chromium into its trivalent form.Bacillus sp.JDM-2-1 could tolerate Cr（Ⅵ）（4800 μg/mL） and S.capitis could tolerate Cr（Ⅵ）（2800 μg/mL）.Both organisms were able to resist Cd^2＋（50 μg/mL）,Cu^2＋（200 μg/mL）,Pb^2＋（800 μg/mL）,Hg^2＋（50 μg/mL） and Ni2＋（4000 μg/mL）.S.capitis resisted Zn^2＋ at 700 μg/mL while Bacillus sp.JDM-2-1 only showed resistance up to 50 μg/mL.Bacillus sp.JDM-2-1 and S.capitis showed optimum growth at pH 6 and 7,respectively,while both bacteria showed optimum growth at 37°C.Bacillus sp.JDM-2-1 and S.capitis could reduce 85% and 81% of hexavalent chromium from the medium after 96 h and were also capable of reducing hexavalent chromium 86% and 89%,respectively,from the industrial effuents after 144 h.Cell free extracts of Bacillus sp.JDM-2-1 and S.capitis showed reduction of 83% and 70% at concentration of 10 μg Cr（Ⅵ）/mL,respectively.The presence of an induced protein having molecular weight around 25 kDa in the presence of chromium points out a possible role of this protein in chromium reduction.The bacterial isolates can be exploited for the bioremediation of hexavalent chromium containing wastes,since they seem to have a potential to reduce the toxic hexavalent form to its nontoxic trivalent form.
