Functional Metagenomics to Mine Soil Microbiome for Novel Cadmium Resistance Genetic Determinants

Metal resistance genes are valuable resources for genetic engineering of bioremediation tools. In this study, novel genetic determinants involved in cadmium (Cd) resistance were identified using a small-insert metagenomic DNA library constructed from an arable soil microbiome. A total of 16 recombinant plasmids harboring 49 putative open reading frames (ORFs) were found to be associated with enhanced Cd tolerance. In addition to several ORFs for ion transport/chelation and stress response, most ORFs were assumed to be associated with non-direct metal resistance mechanisms such as energy metabolism, protein/amino acid metabolism, carbohydrate/fatty acid metabolism, and signal transduction. Furthermore, 13 ORFs from five clones selected at random were cloned and subject to Cd resistance assay. Eight of these ORFs were positive for Cd resistance when expressed in Escherichia coli, among which four ORFs significantly reduced Cd accumulation and one increased Cd enrichment of the host cells. Notably, C1-ORF1, potentially encoding a histidine kinase-like adenosine triphosphatase, was the most effective Cd resistance determinant and reduced host Cd accumulation by 33.9%. These findings highlight the vast capacity of soil microbiome as a source of gene pool for bioengineering. The novel genetic determinants for Cd resistance identified in this study merit further systematic explorations into their molecular mechanisms.     

Induction and Transfer of Enhanced Biodegradation of the Herbicide Napropamide in Soils

In laboratory incubations, the times to 50% loss (DT₅₀) of a first application of napropamide were approximately 25, 45 and 75 days in soil incubated at 25, 15 and 5°C respectively. When treated for a second time, the DT₅₀ values were 4, 7 and 15 days at the same temperatures, irrespective of the temperature of the first incubation. This indicates that enhanced degradation of napropamide in soil can be both induced and expressed at low temperature. A mixed microbial culture able to degrade the herbicide to a single degradation product, identified by HPLC retention time as naphthoxypropionic acid, was obtained from a soil capable of rapid degradation. Addition of a sub-sample of this mixed culture to a previously untreated soil introduced rapid degrading ability. When small amounts of soil capable of rapid degradation were added to previously untreated soil, in both the laboratory and the field, the degradation rate of napropamide increased compared with that in unamended soils.     

Use of a field-scale biofilter for the degradation of the organophosphate insecticide coumaphos in cattle dip wastes

Insecticide wastes generated from livestock dipping operations are well suited for biodegradation processes since these wastes are concentrated, contained, and have no other significant toxic components. A field-scale biofilter capable of treating 15000-litre batches of dip waste containing the acaricide coumaphos was used to reduce the coumaphos concentration in two successive 11000-litre batch trials from 2000 mg litre^-1 to 10 mg litre^-1 in approximately 14 days at 25–29°C. Removal of coumaphos from the biofilter effluent is a function of both physical filtration and biodegradation by the biofilter. However, stoichiometric increases in chloride levels in the effluent as coumaphos concentrations decreased confirmed that coumaphos was being degraded by the biofilter rather than just being filtered out. In subsequent 5500-litre batch experiments, the addition of a vitamin supplement to the biofilter-treated dip resulted in a further decrease in coumaphos concentration to approximately 1 mg litre^-1. Results from incubations of two representative Texas soils with biofilter-treated dip spiked with [benzo-U-¹⁴C] coumaphos revealed that 32–36% of the spiked [¹⁴C] coumaphos was mineralized in the soils after 110 days at 30°C. © 1998 SCI.     

冻土环境下泄漏油污的微生物修复

Oil spills have become a serious problem in cold environments with the ever-increasing resource exploitation, transportation, storage, and accidental leakage of oil. Several techniques, including physical, chemical, and biological methods, are used to recover spilled oil from the environment. Bioremediation is a promising option for remediation since it is effective and economic in removing oil with less undue environmental damages. However, it is a relatively slow process in cold regions and the degree of success depends on a number of factors, including the properties and fate of oil spilled in cold environments, and the major microbial and environmental limitations of bioremediation. The microbial factors include bioavailability of hydrocarbons, mass transfer through the cell membrane, and metabolic limitations. As for the environmental limitations in the cold regions, the emphasis is on soil temperatures, freeze-thaw processes, oxygen and nutrients availability, toxicity, and electron acceptors. There have been several cases of success in the polar regions, particularly in the Arctic and sub-Arctic regions. However, the challenges and constraints for bioremediation in cold environments remain large.     

Biodiversity of the genus Cladophialophora

Cladophialophora is a genus of black yeast-like fungi comprising a number of clinically highly significant species in addition to environmental taxa. The genus has previously been characterized by branched chains of ellipsoidal to fusiform conidia. However, this character was shown to have evolved several times independently in the order Chaetothyriales. On the basis of a multigene phylogeny (nucLSU, nucSSU, RPB1), most of the species of Cladophialophora (including its generic type C. carrionii) belong to a monophyletic group comprising two main clades (carrionii- and bantiana-clades). The genus includes species causing chromoblastomycosis and other skin infections, as well as disseminated and cerebral infections, often in immunocompetent individuals. In the present study, multilocus phylogenetic analyses were combined to a morphological study to characterize phenetically similar Cladophialophora strains. Sequences of the ITS region, partial Translation Elongation Factor 1-α and β-Tubulin genes were analysed for a set of 48 strains. Four novel species were discovered, originating from soft drinks, alkylbenzene-polluted soil, and infected patients. Membership of the both carrionii and bantiana clades might be indicative of potential virulence to humans.Taxonomic novelties: Cladophialophora samoënsis Badali, de Hoog & Padhye, sp. nov., Cladophialophora subtilis Badali & de Hoog, sp. nov., Cladophialophora mycetomatis Badali, de Hoog & Bonifaz, sp. nov., Cladophialophora immunda Badali, Satow, Prenafeta-Boldú, Padhye & de Hoog, sp. nov.     

除草剂阿特拉津污染地下水的生物治理研究

利用从农药厂阿特拉津生产车间排污口污泥中分离出的菌种AT菌，进行了农药阿特拉津污染地下水的微生物治理模拟实验研究。结果表明，在实验条件(t=10℃，pH＝7．5)与野外含水层的条件基本一致的情况下，难于生物降解的污染物质阿特拉津的一次投菌降解率达到26．29％；同时环境因素也随着AT菌作用的变化而变化，其中，DO、Eh、pH随AT菌作用的加强而其值减小。另外，设计了细菌的投放方式以模拟野外条件下的菌种投加条件。模拟实验为野外的原位治理提供了理论和方法依据。     

翘鳞香菇研究进展

翘鳞香菇是新近开发的具有市场潜力的食用菌新品种。本文综述了其栽培技术、固体发酵、深层培养、药理活性和生物修复等方面的研究进展,为其进一步开发应用提供参考。     

细菌阿特拉津氯水解酶基因的功能及其应用

简要介绍了能降解除草剂阿特拉津的细菌的种类和它们的生物降解途径、阿特拉津氯水解酶的功能和定向进化的研究进展,以及阿特拉津氯水解酶基因atzA在污染土壤生物修复和转基因植物研究中的应用。     

Survival and growth of the sea cucumber Holothuria leucospilota Brandt: a comparison between suspended and bottom cultures in a subtropical fish farm during summer

The feasibility of co‐culturing the sea cucumber Holothuria leucospilota Brandt in a subtropical fish farm was investigated in a field study. Sea cucumbers were cultured in the fish farm in cages suspended at 4 m deep (suspended culture) and directly on the seafloor (bottom culture). The survival and growth of the sea cucumbers were monitored twice during the 3‐month, summer experimental period (May 26–August 14, 2010). Results showed that the suspension‐cultured sea cucumbers exhibited excellent survival rate (100%) during the whole study period. There also occurred no mortality in the bottom‐cultured sea cucumbers during the first culture period (May 26–July 13); but all these died from anoxia caused by water column stratification during the second culture period (July 14–August 14). The specific growth rate of the bottom‐cultured sea cucumbers (1.05 ± 0.21 % day^?1) was nearly double that of the suspended culture animals (0.57 ± 0.21 % day^?1) during the first culture period, and the growth rates of the suspended culture sea cucumbers in the second culture periods (0.46 ± 0.24 % day^?1) was only a little lower than that of the first period. The sea cucumbers H. leucospilota could ingest and assimilate sediment with high organic matter content with an average assimilation efficiency of 14.9 ± 3.9%. This study indicated that fish farm detritus can be effectively used as a food source for the sea cucumber and that it can be turned into a valuable secondary crop in the form of the sea cucumber biomass.     

不同工业大麻品种对田间5种重金属吸收积累特性的比较

为了分析不同工业大麻品种对不同重金属富集与转移的差异,以云南5个工业大麻主栽品种（ym1~ym5）为试验材料,修复云南矿区重金属污染严重的农田。结果表明： 5个工业大麻品种中,成熟期的根系对Pb和Cd吸收量最大的为ym1,对As、Cu和Zn吸收量最大的为ym3,而ym5对Pb、Cu、Cd和Zn吸收量皆最小;茎叶对As、Cu和Cd吸收量最大的为ym3,对Pb和Zn吸收量最大的分别为ym1和ym2;种子对Pb和Cd吸收量最大的为ym2,对As和Cu吸收量最大的为ym5,对Zn吸收量最大则为ym3,ym1种子对Pb、As和Cu吸收量皆最小,对Cd、Zn吸收最小的品种分别为ym4和ym2;5个品种表现为除Cu外,茎叶富集系数皆大于根,根系向茎叶的转运系数均大于1。研究表明,ym1可作为Pb污染修复植物,ym3可作为As、Zn、Cu和Cd污染修复的适推品种。