The effect of bacterial glutathione S-transferase on morpholine degradation

Glutathione S-transferases (GSTs) constitute a large family of enzymes that catalyze the addition of glutathione to endogenous, or xenobiotic, often toxic electrophilic compounds. The effect of this enzyme in facilitating polychlorinated biphenyls degradation has been studied previously. Here the effects of induced cell-free extracts of Acinetobacter calcoaceticus and Pseudomonas aeruginosa (grown on hexadecane), and E. coli BL21 (induced with pGEX-2T plasmid on isothiopropylgalactoside) were recruited to facilitate morpholine degradation by Mycobacterium and were compared with non-induced strains. The results showed that all induced strains had significantly more GST activity compared to non-induced ones, and the strain with most GST activity, A. calcoaceticus BS, removed morpholine faster. Eukaryotic GST gene expressed in E. coli BL21 also could facilitate morpholine degradation by Mycobacterium, The same experiments performed with cell-free extracts of non-induced cells did not show any significant effects on morpholine removal. These results showed that there is a correlation between GST activity and acceleration of morpholine degradation.     

The microbial degradation of benzothiazoles

The biodegradation of benzothiazoles by pure and mixed microbial cultures derived from activated sludge has been studied. The degradation of 2-aminobenzothiazole (ABT) by both pure and mixed bacterial cultures has been demonstrated for the first time. ABT is degraded to give high yields of ammonia and sulphate (87 and 100 %, respectively of the theoretical yield). We also report for the first time the isolation of a pure bacterial culture PA, thought to be a strain of Rhodococcus , capable of growing on benzothiazole (BTH) itself as a sole carbon, nitrogen and energy source. Evidence is presented to suggest that this organism degrades BTH via the meta-cleavage pathway. The Rhodococcus PA degrades BTH but only releases a small proportion (5%) of the sulphur as sulphate. Mixed cultures containing this organism released ca 100% of the sulphur as sulphate, suggesting that other members of the consortium catalyse conversion of a sulphur-containing intermediate to sulphate. 2-Mercaptobenzothiazole (MBT) could not act as a growth substrate for any of the cultures studied but some could cause biotransformation of MBT to some extent. Attempts to obtain cultures degrading ABT and BTH from polluted river water were unsuccessful.     

Plasmid-assisted morpholine degradation by Pseudomonas fluorescens CAS 102

A fast-growing Pseudomonas fluorescens CAS102, isolated by enrichment technique from polluted soil, effectively utilized morpholine as the energy source. The strain was able to grow in high concentrations of morpholine but accumulation of ammonia inhibited its growth and complete mineralization. The molar conversion ratio of morpholine to ammonia was 1:0.82. The organism harboured a single, multiple antibiotic- and heavy metal-resistance 140kb plasmid which was resistant to curing. Transformation studies showed that the morpholine degradative phenotype was expressed only in Pseudomonas putida and not in Escherichia coli. Growth studies on different degradative intermediates of morpholine suggested that plasmid-encoded genes were involved in the heterocyclic ring cleavage and the remaining reactions were mediated by chromosomal genes.     

Plasmid-assisted morpholine degradation by Pseudomonas fluorescens CAS 102

A fast-growing Pseudomonas fluorescens CAS102, isolated by enrichment technique from polluted soil, effectively utilized morpholine as the energy source. The strain was able to grow in high concentrations of morpholine but accumulation of ammonia inhibited its growth and complete mineralization. The molar conversion ratio of morpholine to ammonia was 1:0.82. The organism harboured a single, multiple antibiotic- and heavy metal-resistance 140kb plasmid which was resistant to curing. Transformation studies showed that the morpholine degradative phenotype was expressed only in Pseudomonas putida and not in Escherichia coli. Growth studies on different degradative intermediates of morpholine suggested that plasmid-encoded genes were involved in the heterocyclic ring cleavage and the remaining reactions were mediated by chromosomal genes.     

环境雌激素的微生物代谢

环境雌激素作为一类重要的新型环境污染物,可通过干扰生物体的内分泌系统危害生物体健康。微生物降解是去除环境雌激素与进行环境修复的主要手段。本文归纳整理了目前研究较深入的雌激素降解微生物,类比阐述了其预测的降解通路与降解机制,并对后续环境雌激素降解研究的主要内容与方向进行了展望。     

The microbial degradation of halogenated diaryl ethers

The structurally related polyhalogenated diaryl ethers such as diphenyl ethers (DEs), dibenzofurans (DFs), and dibenzo-p-dioxins (DDs) are regarded, due to their physicochemical and toxicological properties, as a class of compounds giving reason for serious environmental concern. While the nonhalogenated basic structures are biodegradable under aerobic conditions, there is the need for rather specialized strains to mineralize the halogenated derivatives. Certain halogenated metabolites might cause serious problems such as having inhibitory effects upon the degradation. Anaerobic methanogenic consortia do have the ability to almost completely dehalogenate even polyhalogenated congeners. It has been shown that certain fungi are capable of transforming chlorinated DFs and DDs by the activity of nonspecific enzymes such as lignin-peroxidases.     

The microbial degradation of azo dyes: minireview

The removal of dyes in wastewater treatment plants still involves physical or chemical processes. Yet numerous studies currently exist on degradation based on the use of microbes—which is a well-studied field. However progress in the use of biological methods to deal with this environmentally noxious waste is currently lacking. This review focuses on the largest dye class, that is azo dyes and their biodegradation. We summarize the bacteria identified thus far which have been implicated in dye decolorization and discuss the enzymes involved and mechanisms by which these colorants are broken down.     

The microbial degradation of silk: a laboratory investigation

A few bacterial species, mostly gram-negatives, were found to attach themselves and grow on silk buried in soil. On the contrary, no fungi were isolated in such experiments. Growth was more abundant on raw silk (composed of sericin and fibroin) than on degummed silk (fibroin only) indicating that the majority of these bacteria use sericin rather than fibroin for growth. Electron microscopy demonstrated that bacteria formed a biofilm on the fabric and caused extensive damage to the fibers resulting in considerable reduction in the mechanical properties. Of the three main bacterial species isolated from silk exposed to soil or by enrichment cultures of silk cocoons, only Pseudomonas (Burkholderia) cepacia appeared to be able to use fibroin as a sole source of carbon and nitrogen for growth. Indeed, in laboratory experiments, pure cultures of P. cepacia were found to form a well-developed biofilm on fibroin, to hydrolyze fibroin, and to produce an extracellular enzyme attacking this protein. The reported data indicate that bacteria but not fungi may attack and degrade silk proteins and thus cause irreversible damage to silk artifacts of artistic or historical interest.     

六氯-1,3-丁二烯的微生物降解研究进展

六氯-1,3-丁二烯(hexachlorobutadiene,HCBD)是一种有毒有害的脂肪族氯代烃,曾经作为杀虫剂、除草剂、变压器油和传热流体等化学工业产品的重要成分被广泛应用于生产生活。HCBD因满足《关于持久性有机污染物的斯德哥尔摩公约》中风险筛选标准(如毒性、持久性、远距离环境迁移和生物累积性等),缔约方于2015年第七次会议中将其增列为持久性有机污染物,2017年又将其列入该公约的附件Ｃ以控制其环境排放量。目前关于HCBD的环境归趋仍是研究热点,但是对于HCBD的微生物降解转化机制尚缺乏深入研究。鉴于此,本文重点回顾并讨论了地下水、底泥等厌氧环境中已报道的HCBD微生物降解转化途径、速率及机制,并从热力学角度阐述HCBD及其降解产物作为电子受体通过还原性脱氯反应被厌氧脱卤微生物代谢转化的可行性。最后,本文根据现有研究结果,提出微生物厌氧降解HCBD的研究展望,包括多组学技术解析HCBD降解功能菌群结构和潜在互作机制、HCBD厌氧降解微生物的分离与纯化,以及HCBD厌氧降解菌剂的开发与污染场地原位生物修复应用等。     

微生物降解塑料的研究进展

塑料广泛应用于人类的生活中,其中约80％的塑料垃圾被填埋,最终成为陆地和海洋垃圾.由于管理与处置不善,这些废弃物造成了巨大的环境污染,目前回收再利用是较好的处置方式,但对某些塑料废弃物并没有妥善的处置方式.生物降解作为环境友好的处置方式,具有巨大的应用潜力.本文对聚对苯二甲酸乙二醇酯、聚乙烯、聚氯乙烯、聚丙烯、聚苯乙烯...     

Phenomenological principles of microbial lignin degradation

This paper intends to focus the attention to characteristic features of microbial lignin degradation from the phenomenological point of view. Six fundamental principles are discussed under special consideration of white-rot fungi. The necessity of mycelial growth and the formation, secretion, and extracellular action of peroxidases are main requirements for a successful microbial attack on polymeric lignin.     

Biochemistry of microbial polyvinyl alcohol degradation

Effect of minor chemical structures such as 1,2-diol content, ethylene content, tacticity, a degree of polymerization, and a degree of saponification of the main chain on biodegradability of polyvinyl alcohol (PVA) is summarized. Most PVA-degraders are Gram-negative bacteria belonging to the Pseudomonads and Sphingomonads, but Gram-positive bacteria also have PVA-degrading abilities. Several examples show symbiotic degradation of PVA by different mechanisms. Penicillium sp. is the only reported eukaryotic degrader. A vinyl alcohol oligomer-utilizing fungus, Geotrichum fermentans WF9101, has also been reported. Lignolytic fungi have displayed non-specific degradation of PVA. Extensive published studies have established a two-step process for the biodegradation of PVA. Some bacteria excrete extracellular PVA oxidase to yield oxidized PVA, which is partly under spontaneous depolymerization and is further metabolized by the second step enzyme (hydrolase). On the other hand, PVA (whole and depolymerized to some extent) must be taken up into the periplasmic space of some Gram-negative bacteria, where PVA is oxidized by PVA dehydrogenase, coupled to a respiratory chain. The complete pva operon was identified in Sphingopyxis sp. 113P3. Anaerobic biodegradability of PVA has also been suggested.     

微生物降解磺胺甲恶唑的研究进展

抗生素是一类难降解、低浓度就有高生态毒性效应的化合物,近年来被归为新型环境污染物,其环境残留与去除备受关注。作为广泛使用的抗生素之一,磺胺甲恶唑在水土环境中的残留量不断增加,检出率也越来越高。研究表明,磺胺甲恶唑是少数几种可被微生物降解的抗生素之一,微生物降解法是最具潜力的残留磺胺甲恶唑去除手段。本文总结了磺胺甲恶唑在土壤、沉积物、活性污泥、混合菌群、酶等条件下的降解及已分离的具有降解能力的单菌株对磺胺甲恶唑的降解情况,包括其降解效率、降解条件等,归纳了目前磺胺甲恶唑微生物降解的主要分类,并讨论了影响磺胺甲恶唑降解的两个特有因素。指出从分子生物学及生物信息学角度研究其降解途径,降解菌、降解菌群的人工构建及其在含磺胺甲恶唑污水处理中的应用与效果评价等应为今后磺胺甲恶唑生物降解与应用研究的重点。     

Thermophilic microbial degradation of polyethylene succinate

This paper examined the biodegradability of a new aliphatic polyester, polyethylene succinate (PES), at a high incubation temperature of 50°C. The distribution and population of total colonies and of PES degrading micro organisms on polymer-emulsified agar plates were determined using the plate count and clear zone methods. The PES-decomposers were present in six of 10 soil samples and the total number ranged from 2.0×104 to 2.2×106 c.f.u./g of samples. Degrading microorganisms constituted between 20 and 80% of the total colonies on PES–agar plates. A single PES-degrading strain, TT96, was isolated and tested for its biodegrading capacity on PES powder and on other aliphatic polyesters: poly(beta-hydroxybutyrate) (PHB), polycaprolactone (PCL), poly(butylene succinate) (PBS), and poly(L-lactide) (PLA). Degraded films of PES and PBS were presented and compared using scanning electron microscopy. Strain TT96 was able to create clear zones on all the polymers used, except on PHB-agar plates. Liquid culture test after 2 weeks showed that TT96 completely degraded PCL powder but had very little activity on other samples. Scanning electron micrograph confirmed the microbial attack of TT96 on PES and PBS films. PES film surfaces were degraded more uniformly compared to PBS films which were decomposed only in some parts.     

Thermophilic microbial degradation of polyethylene succinate

This paper examined the biodegradability of a new aliphatic polyester, polyethylene succinate (PES), at a high incubation temperature of 50°C. The distribution and population of total colonies and of PES degrading micro organisms on polymer-emulsified agar plates were determined using the plate count and clear zone methods. The PES-decomposers were present in six of 10 soil samples and the total number ranged from 2.0×104 to 2.2×106 c.f.u./g of samples. Degrading microorganisms constituted between 20 and 80% of the total colonies on PES–agar plates. A single PES-degrading strain, TT96, was isolated and tested for its biodegrading capacity on PES powder and on other aliphatic polyesters: poly(beta-hydroxybutyrate) (PHB), polycaprolactone (PCL), poly(butylene succinate) (PBS), and poly(L-lactide) (PLA). Degraded films of PES and PBS were presented and compared using scanning electron microscopy. Strain TT96 was able to create clear zones on all the polymers used, except on PHB-agar plates. Liquid culture test after 2 weeks showed that TT96 completely degraded PCL powder but had very little activity on other samples. Scanning electron micrograph confirmed the microbial attack of TT96 on PES and PBS films. PES film surfaces were degraded more uniformly compared to PBS films which were decomposed only in some parts.     

The use of yeast for microbial degradation of some selected mycotoxins

Several biodegradation experiments were carried out using 10 different yeast strains.Saccharomyces spp., Kluyveromyces spp. andRhodotorula spp. were tested for biodegradation of selected mycotoxins (ochratoxin A, nivalenol, deoxynivalenol and fumonisin B₁) standardsin vitro. There was confirmed that some yeast strains are able to degrade some mycotoxins. However, great differences between individual strains were observed. Moreover, 12Saccharomyces cerevisiae strains were tested for their potential capability to degrade zearalenone and fumonisins in Sabouraud broth. Two strains were capable to degrade zearalenone totally, one strain decreased the mycotoxin concentration up to 25%, and one strain up to 75% of original amount. Two strains were capable to degrade fumonisins partially.     

The microbial degradation of chlorophenolic preservatives in spent,pressure-treated timber

The reduction of pentachlorophenol in treated timber, after inoculation with pentachlorophenol-degrading bacterial species,Rhodococcus chlorophenolicus andFlavobacterium sp., and the white-rot fungusPhanerochaete chrysosporium, was monitored in solid substrate systems and in liquid culture suspensions. In solid substrate systems there was no significant pentachlorophenol degradation by the bacterial species under a variety of conditions. Under similar conditions,Phanerochaete chrysosporium transformed over 80% of the starting concentration of 500 ppm to pentachloroanisole. In liquid culture suspensions however, mid-exponential phaseFlavobacterium sp. cells were able to degrade over 99% of the pentachlorophenol in sawdust and wood chips due to the extraction of PCP from the timber as a water soluble salt. There were however no significant changes in the chlorinated dioxin components during this treatment.Abbreviations ATTC American type culture collection - AWPA American Wood Preservers' Association - DSM Deutsche Sammlung für Mikroorganismen - GC/MS gas chromatograph/mass spectrometer - HpCDD heptachlorodibenzo-p-dioxin - HpCDF heptachlorodibenzofuran - HxCDD hexachlorodibenzo-p-dioxin - HxCDF hexachlorodibenzofuran - ¹³C-OCDD carbon 13-labelled octachlorodibenzo-p-dioxin - OCDD octachlorodibenzo-p-dioxin - OCDF octachlorodibenzofuran - PCDDs polychlorinated dibenzo-p-dioxins - PCDFs polychlorinated dibenzofurans - PCP pentachlorophenol - PnCDD pentachlorodibenzo-p-dioxin - PnCDF pentachlorodibenzofuran - TCDD tetrachlorodibenzo-p-dioxin - TCDF terachlorodibenzofuran - TeCP tetrachlorophenol - WHC water holding capacity - w/v weight for volume ratio