Fundamentals and Application Potential of Arsenic-Resistant Bacteria for Bioremediation in Rhizosphere: A Review

As a hazardous environmental metalloid toxicant, arsenic (As)—at elevated levels in water and soil—has created a major public health concern through its entry into the food chain by accumulation in crops. Among the various methods reported thus far for reclamation of As-contaminated crop fields, bioremediation using bacteria with plant-growth-promoting traits has been found to be a most promising solution. There is every possibility that bacterial isolates with the ability to remove or immobilize As could be used for successful bioremediation. However, bioremediation needs to define its boundaries between promise and field application, as most studies have been restricted to laboratory results only. Rhizosphere interactions play a critical role in monitoring As bioavailability to crop plants, thus a better understanding of it might improve rhizoremediation technologies. The challenges rely on the application of these novel approaches under field conditions. Despite some limitations, the prospect for successful stimulation and exploitation of microbial metabolism for As rhizoremediation appears to be very promising.     

Enhancement of Sulphide Production in Anaerobic Packed Bed Bench-scale Biofilm Reactors by Sulphate Reducing Bacteria

Two biofilm reactors, using pumice stone and Poraver as biofilm supports, were run, based on the optimization of sulphide production using a factorial design. The maximum H₂S concentrations reached were 10 and 15 mm, respectively, both being appropriate for metal precipitation in effluents. The set-up of the pumice stone biofilm reactor is suitable for application in the mining area in the Bolivian Andean region, where this material is widely available. The use of specific primers for sulphate-reducing bacteria groups permits the identification of the sulphide-producing bacteria present in biofilms.     

Ecological role of Acinetobacter calcoaceticus GSN3 in natural biofilm formation and its advantages in bioremediation

This study assessed the role of a new Acinetobacter calcoaceticus strain, GSN3, with biofilm-forming and phenol-degrading abilities. Three biofilm reactors were spiked with activated sludge (R1), green fluorescent plasmid (GFP) tagged GSN3 (R2), and their combination (R3). More than 99% phenol removal was achieved during four?weeks in R3 while this efficiency was reached after two and four further operational weeks in R2 and R1, respectively. Confocal scanning electron microscopy revealed that GSN3-gfp strains appeared mostly in the deeper layers of the biofilm in R3. After four?weeks, almost 7.07?×?10⁷ more attached sludge cells were counted per carrier in R3 in comparison to R1. Additionally, the higher numbers of GSN3-gfp in R2 were unable to increase the efficiency as much as measured in R3. The presence of GSN3-gfp in R3 conveyed advantages, including enhancement of cell immobilization, population diversity, metabolic cooperation and ultimately treatment efficiency.     

结合光谱法在DMIs类杀真菌剂筛选中的应用

为建立一种快捷和准确的方法用于新型杀真菌剂的筛选,以外源表达的稻瘟菌羊毛甾醇14α-去甲基化酶为靶酶,以市售烯唑醇、戊唑醇、三唑醇、三唑酮为DMIs类杀真菌剂代表,分析了靶酶活性、靶酶纯度和靶酶浓度对二者结合光谱的影响,并与生物测试结果比较分析其可靠性。结果表明靶酶的高活性、无其他P450干扰和合适的靶酶浓度是获得准确结合光谱的必要条件。烯唑醇、戊唑醇、三唑醇、三唑酮与靶酶结合常数（K,/i>_d）分别为0.143μmol/L、0.24μmol/L、0.257μmol/L、0.307μmol/L,该结果与其对稻瘟菌生长抑制能力(120h-EC₅₀)显著相关,证明结合光谱法可作为一种简便可靠的DMIs类杀真菌剂筛选方法。     

结合光谱法在DMIs类杀真菌剂筛选中的应用

为建立一种快捷和准确的方法用于新型杀真菌剂的筛选,以外源表达的稻瘟菌羊毛甾醇14α-去甲基化酶为靶酶,以市售烯唑醇、戊唑醇、三唑醇、三唑酮为DMIs类杀真菌剂代表,分析了靶酶活性、靶酶纯度和靶酶浓度对二者结合光谱的影响,并与生物测试结果比较分析其可靠性。结果表明靶酶的高活性、无其他P450干扰和合适的靶酶浓度是获得准确结合光谱的必要条件。烯唑醇、戊唑醇、三唑醇、三唑酮与靶酶结合常数(Kd)分别为0.143μmol/L、0.24μmol/L、0.257μmol/L、0.307μmol/L,该结果与其对稻瘟菌生长抑制能力(120h-EC50)显著相关,证明结合光谱法可作为一种简便可靠的DMIs类杀真菌剂筛选方法。     

失重对细菌的影响及机制研究进展

失重是主要空间环境因素之一,人体及航天器会携带细菌到太空。失重会造成沙门氏菌、大肠埃希菌、铜绿假单胞菌等表型改变,出现增殖、毒力、生物被膜和环境抵抗力等方面的改变。而且,失重会引起人体免疫力下降,被细菌感染机会增加。文章就失重对细菌的影响及机制进行综述,以期能为相关研究提供新思路。     

Molecular Identification and Biofilm-Forming Ability of Culturable Aquatic Bacteria In Microbial Biofilms Formed in Drinking Water Distribution Networks

Drinking water distribution networks are known to harbor microbial biofilms. The aim of the present work is to (i) identify the culturable bacteria presented in the drinking-water distribution network, (ii) investigate the ability of isolated bacteria to form biofilm under some environmental stress conditions and some eliminating or removing treatments. To achieve it, 57 strains were isolated from biofilm (43 isolates) and water samples (14 isolates) collected from five stations in drinking-water distribution network in Taif city, Kingdom of Saudi Arabia (KSA). Partial sequences of 16S rRNA gene in the 57 isolates ensured the presence of only 22 different strains in biofilm samples. Among these strains, only 14 strains were also detected in water samples. Gram-negative Aeromonas hydrophila was the most occurred bacterium in the microbial biofilm obtained from the purified-water storage tanks followed by Gram-negative Pseudomonas sp. Gram-positive Bacillus subtilis was the most occurred bacterium in the microbial biofilm collected from the ends of the distribution pipes. Among the 22 isolated strains, 13 strains were strong biofilm producers at 30 and 37°C. The effects of environmental stresses including nutrient starvation (diluted TSB, 20:1), heating (100°C for 10 min), UV-treatment (240 nm for 10 min) and dynamic incubation (150 rpm min^?1) on the formation of biofilm were also investigated. These conditions affected the biofilm formation ability of the isolated strains at different levels. Nutrient starvation enhanced biofilm formation by most of the isolates. Among some biofilm deforming treatments, SDS and trypsin had considerable effects on preventing biofilm formation by most of the isolated strains. In conclusion, the results of the present work indicated that not all biofilm strains released from biofilm to the drinking water. Also, not all biofilm strains were able to form biofilm. Most of isolated bacteria had ability to form biofilm at suboptimum temperature of growth. These results may provide basic information on formation of microbial biofilms and overcome the problem of deteriorating of water quality in the drinking-water distribution networks.     

柴油降解细菌的分离及其降解能力初探

从含油土壤中,筛选出能以0#柴油为惟一碳源的2株柴油降解菌,经鉴定分别为假单胞菌(Pseudomonoussp.)和芽孢杆菌(Bacillussp.)。通过其降解能力的测试,假单胞杆菌属细菌A8的降解能力较强;在含油浓度ρ=10g/L的摇瓶试验中,培养7d后其除油率分别为18%和31%。在含油浓度1%的土壤中,2株菌均能正常生长和繁殖,接种30d除油率分别为35%和48.3%。     

Trichloroethylene Degradation by Toluene-Oxidizing Bacteria Grown on Non-aromatic Substrates

The potential of trichloroethylene (TCE) to induce and non-aromatic growth substrates to support TCE degradation in five strains (Pseudomonas mendocina KR1, Ralstonia pickettii PKO1, Pseudomonas putida F1, Burkholderia cepacia G4, B. cepacia PR1) of toluene-oxidizing bacteria was examined. LB broth and acetate did not support TCE degradation in any of the wild-type strains. In contrast, fructose supported the highest specific levels of TCE oxidation observed in each of the strains tested, except B. cepacia G4. We discuss the potential mechanisms and implications of this observation. In particular, cells of P. mendocina KR1 degraded significant amounts of TCE during cell growth on non-aromatic substrates. Apparently, TCE degradation was not completely constrained by any given factor in this microorganism, as was observed with P. putida F1 (TCE was an extremely poor substrate) or B. cepacia G4 (lack of oxygenase induction by TCE). Our results indicate that multiple physiological traits are required to enable useful TCE degradation by toluene-oxidizing bacteria in the absence of aromatic cosubstrates. These traits include oxygenase induction, effective TCE turnover, and some level of resistance to TCE mediated toxicity.     

长链烷烃降解菌的降解特性

对长链烷烃降解菌的降解能力和摄取模式进行了研究。评价14株烃降解菌利用中长链烃生长的能力,发现只有少数烃降解菌能够获得良好生长,其中Mycobacterium fortuitum514,Pseudomonas aeruginosa1785和Pseudomonas marginata766等3株菌能够高效降解C20到C33的长链烷烃。辛烷不能支持这些长链烷烃降解菌的生长,说明其烃氧化酶与Pseudomonas oleovorans的OCT质粒编码的单氧酶不同。此外,M.fortuitum不产胞外表面活性剂,而P.aeruginosa和P.marginata则是表面活性剂产生菌,然而三者在以烃为碳源生长时均显示出很高的细胞表面疏水性。根据生长现象分析3株菌采用了不同的烷烃摄取模式。     

Studies on the Mode of Action of Organophosphorus Fungicide,Kitazin

Studies were conducted on the influence of Kitazin analogues on the incorporation of ¹⁴C-glucosamine into the mycelial cell wall fraction of Pyricularia oryzae. Compounds of thiolates and phosphates, both having in vitro inhibitory activities toward the mycelial growth, inhibited the incorporation, whereas those of thionates and dithioates, either having no fungitoxicity, did not inhibit the incorporation. Mycelia of P. oryzae treated with Kitazin-P (S-benzyl O,O′-diisopropyl phosphrothioate; IBP) accumulated about twice as much an amino sugar derivative as untreated ones. Mycelia treated with thiono or dithio analogues, which have no fungitoxicity, showed no accumulation. The accumulated substance gave a identical spot with authentic UDP-N-acetyl glucosamine on paper chromatograms developed with four solvent systems.     

Complex Dielectric Properties of Sulfate-Reducing Bacteria Suspensions

Sulfate-reducing bacteria (SRB) can potentially enhance the remediation of heavy metals in the subsurface. Previous geophysical research has demonstrated the sensitivity of electrical measurements to SRB-mediated mineral transformation in porous media. However, the inherent dielectric properties of SRB and their direct contribution to the electrical properties of porous media are poorly understood. We studied the complex dielectric properties of SRB (Desulfovibrio vulgaris) suspensions at different concentrations and at different growth stages using a two-electrode dielectric spectroscopy measurement over the frequency range of 20 Hz to 1 MHz. Our results show higher dielectric responses (relative dielectric permittivity, real and imaginary conductivity) occurred with higher bacteria concentration at frequencies <10 kHz. Additionally, permittivity and conductivity both decreased as cells aged from mid-log phase to late stationary phase. Our results suggest that dielectric spectroscopy measurements can be used to noninvasively monitor biomass and various growth stages of SRB. Our work advances the interpretation of electrical signals associated with SRB observed in the subsurface.     

七株聚丙烯酰胺降解菌对PAM的降解性能评价

研究了从油田产聚合物污水和污泥中分离到的7株聚丙烯酰胺（PAM）降解菌对纯PAM的降解效果。结果表明,PAM微生物降解的过程中,会伴随有pH的降低。由于7株菌组成的微生物群落对PAM的生物降解作用,使得培养基中的PAM的运动粘害怂650．mm^2．／s降低至100mm^2／s左右。添加液蜡或酵母膏等导致微生物菌群的共代谢作用,可加快PAM的生物降解。     

Effect on the Medium Salinity on Oil Degradation by Nocardioform Bacteria

Oil degradation by cultures of Rhodococcus erythropolisand Dietzia mariswas found to depend on the NaCl concentration in the medium. Optimal utilization of turbine oil by R. erythropolisand D. mariswas observed at 0.5 and 2 to 5% NaCl concentration, respectively. Mineral oil and a mixture of paraffins (C₁₄–C₁₈) were utilized within a broader range of the medium salinity. As shown by fluorescent microscopy, D. mariscolonies formed on the oil drop surface, whereas R. erythropoliscells penetrated the drops. The strains studied may populate various ecological niches in oil-containing ecosystems. They are promising for the development of microbial preparations for cleaning the environment from oil pollution.     

铁还原菌降解石油烃的研究进展

铁还原菌是指能够利用细胞外Fe(III)作为末端电子受体,通过氧化有机物将Fe(III)还原为Fe(II)微生物的总称。铁还原作用广泛存在于土壤、河流、海洋、地表含水层以及高温高压的地下深部油藏。在厌氧或兼性厌氧条件下,Fe(III)还原耦合有机物的降解,对铁、碳元素的生物地球化学循环具有重要意义。本文介绍了铁还原菌的多样性和铁还原作用机理,综述了铁还原菌在石油烃降解方面的研究进展。此外,还总结了铁还原菌在生物修复中的潜在作用,并对未来的研究方向进行了展望。     

高效降解石油细菌的分离鉴定及降解能力的研究

目的:为获得高效降解原油的菌株,从石油污染严重的土壤中采样,富集分离得到原油降解菌,并初步考察它们降解原油的能力。方法:通过富集培养、多次筛选分离得到三株优势菌,编号为SWH-1、SWH-2和SWH-3。通过16S rDNA序列分析和NCBI数据库的Blast比对分析,对其鉴定到种。通过差量法测定它们在室内摇瓶中对原油的降解率。结果:经鉴定,这三株菌分别为枯草芽孢杆菌(Bacillus subtillus)、多食鞘氨醇杆菌(Sphingobacterium multivorum)和嗜温鞘氨醇杆菌(Sphingobacterium thalpophi-lum)。在0.5g/L的原油培养基内培养1w,SWH-1和SWH-2的降解率较高,分别为33.89%和46.31%。将这两株菌进行混合培养降解原油,降解率高达51.73%。结论:所筛选到的枯草芽孢杆菌和多食鞘氨醇杆菌在生物修复方面具有很好的应用潜力,而且多食鞘氨醇杆菌在石油降解方面的报道尚属首次。     

Degradation of hydrocarbons and alcohols by Rhodococcus erythropolis DCL14: A comparison in scale performance

The degradation of alkanes and alcohols by Rhodococcus erythropolis DCL14 growing cells was tested at different reactor scales, ranging from a 2-L fermenter to 300 µL 96-well plates. The highest growth rates were attained in the fermenter, where pH, temperature and aeration rate, in particular, are monitored and controlled. However, the results acquired in reactors smaller than 100 mL indicate that these reactors may be successfully used in testing carbon sources, since the normalized results obtained with the different carbons sources were maintained in the 100–0.3 mL range. This study also shows the great potential of R. erythropolis DCL14 cells to degrade a wide range of alcohols and alkanes, which may be used in bioremediation of contaminated sites.     

Degradation of hydrocarbons and alcohols by Rhodococcus erythropolis DCL14: A comparison in scale performance

The degradation of alkanes and alcohols by Rhodococcus erythropolis DCL14 growing cells was tested at different reactor scales, ranging from a 2-L fermenter to 300 µL 96-well plates. The highest growth rates were attained in the fermenter, where pH, temperature and aeration rate, in particular, are monitored and controlled. However, the results acquired in reactors smaller than 100 mL indicate that these reactors may be successfully used in testing carbon sources, since the normalized results obtained with the different carbons sources were maintained in the 100-0.3 mL range. This study also shows the great potential of R. erythropolis DCL14 cells to degrade a wide range of alcohols and alkanes, which may be used in bioremediation of contaminated sites.