嗜麦芽窄食单胞菌对铜镉的吸附特性与离子交换

研究了投菌量、金属浓度和戊二醛浓度对嗜麦芽窄食单胞菌吸附水体中Cu2+和Cd2+特性的影响,分析了重金属生物吸附、NO3-去除与菌体离子释放的关联,从离子吸附、交换、转化与释放的角度探讨了重金属生物吸附机制.结果表明嗜麦芽窄食单胞菌对Cu2+和Cd2+吸附性能良好,0.2 g·L-1干重菌体处理浓度为0.05 mmol·L-1的Cu(NO3)2和Cd(NO3)2溶液120 min后,Cu2+和Cd2+的吸附率分别达96.3%和83.9%.菌体对Cu(NO3)2和Cd(NO3)2溶液的吸附过程存在Cu2+和Cd2+的表面吸附与胞内运输、NO3-胞内积累、NO3-还原为NO2-等行为,而且Cu2+和Cd2+的胞内运输、NO3-积累和还原需要消耗能量,并会促进Cl-、PO43-、SO42-、Na+、NH4+、K+和Ca2+等离子的释放.红外光谱分析表明菌体酰胺基、羟基与羧基均参与了Cu2+和Cd2+的吸附.X-光电子能谱分析显示吸附后Cu2+和Cd2+的价态不发生变化.     

The exposition of a calcareous Mediterranean soil to toxic concentrations of Cr, Cd and Pb produces changes in the microbiota mainly related to differential metal bioavailability

The involvement of the bacterial community of an agricultural Mediterranean calcareous soil in relation to several heavy metals has been studied in microcosms under controlled laboratory conditions. Soil samples were artificially polluted with Cr(VI), Cd(II) and Pb(II) at concentrations ranging from 0.1 to 5000 mg kg⁻¹ and incubated along 28 d. The lowest concentrations with significant effects in soil respirometry were 10 mg kg⁻¹ Cr and 1000 mg kg⁻¹ Cd and Pb. However, only treatments showing more than 40% inhibition of respirometric activity led to significant changes in bacterial composition, as indicated by PCR-DGGE analyses. Presumable Cr- and Cd-resistant bacteria were detected in polluted microcosms, but development of the microbiota was severely impaired at the highest amendments of both metals. Results also showed that bioavailability is an important factor determining the impact of the heavy metals assayed, and even an inverted potential toxicity ranking could be achieved if their soluble fraction is considered instead of the total concentration. Moreover, multiresistant bacteria were isolated from Cr-polluted soil microcosms, some of them showing the capacity to reduce Cr(VI) concentrations between 26% and 84% of the initial value. Potentially useful strains for bioremediation were related to Arthrobacter crystallopoietes, Stenotrophomonas maltophilia and several species of Bacillus.     

噻吩磺隆降解菌FLX的分离鉴定及降解特性

从生产噻吩磺隆的农药厂内土壤中采取土样,经驯化富集后筛选到1株能高效降解噻吩磺隆的细菌FLX,根据表型特征、生理生化特性及16SrDNA分析,鉴定FLX初步为寡养单胞菌(Stenotrophomonas sp.).FLX能在含50mg/L噻吩磺隆的基础盐液体培养基中降解噻吩磺隆,48h降解率达83.34%.FLX降解噻吩磺隆的最适pH值为7.0,最适温度为35℃,在所试的金属离子中,Zn²⁺、Al³⁺、Cu²⁺、Ba²⁺、Fe_³⁺等对FLX的降解影响较小;Hg²⁺,Co²⁺则抑制FLX的生长与降解.酶的定域实验表明,该菌中噻吩磺隆水解酶为胞内酶.     

十溴联苯醚共存条件下水中Zn(Ⅱ)的生物吸附

研究了十溴联苯醚(BDE-209)共存条件下嗜麦芽窄食单胞菌对水中Zn2+的吸附特性,并通过对菌体进行失活处理、红外光谱和X-光电子能谱分析,探讨了吸附机理。结果表明,Zn2+的吸附符合Freundlich吸附模式;嗜麦芽窄食单胞菌对Zn2+吸附作用明显,2.5 g/L菌体在2 h时,对初始浓度为2.0 mg/L Zn2+的去除率达92%。BDE-209对菌体吸附Zn2+有一定的抑制作用。各因素对嗜麦芽窄食单胞菌吸附Zn2+的影响程度由大到小依次为:投菌量>pH>BDE-209浓度。菌体对Zn2+的吸附除表面吸附外,还存在跨细胞壁细胞膜的主动运输和积累等作用。菌体中的酰胺基与羟基均参与了Zn2+吸附,而且菌体表面Ca2+与Zn2+发生了离子交换,吸附后Zn2+的价态不变。     

嗜根寡养单胞菌DSM14405T对高浓度Cr(Ⅵ)的抗性及其还原特性分析

为了寻找植物-微生物联合治理Cr（VI）污染的合适微生物,分析了一株植物根际促生菌——嗜根寡养单胞菌DSM 14405^T（Stenotrophomonas rhizophila DSM 14405^T）对不同浓度Cr（VI）的还原能力、Cr（VI）还原最适培养条件、对连续投加Cr（VI）的还原能力及高浓度Cr（VI）处理不同时间的转录组变化.结果表明,嗜根寡养单胞菌DSM 14405^T在24 h内对10、50、200和500 mg·L^-1 Cr（VI）的还原率分别为100%、92.4%、26.2%和16.5%,且在30℃、pH=7.5、转速180 r·min^-1条件下培养能最经济、高效地还原Cr（VI）.该菌能在64 h内完全还原2次所投加的50 mg·L^-1的Cr（VI）,第3次投加后仅能还原55.2%左右.比较转录组学分析可得,200 mg·L^-1Cr（VI）作用下,嗜根寡养单胞菌DSM 14405^T细胞表现出显著的抗性.具体表现为：大幅度上调胞内消除有毒自由基的相关基因、DNA修复相关基因以防止DNA因自由基受损,同时下调细胞组分及蛋白代谢等与细胞抗性相关性低的通路.并且,随着Cr（VI）的还原和细胞对环境的适应,Cr（VI）抗性相关基因及通路的调节在长时暴露中明显少于短时暴露.本研究为Cr（VI）污染的原位植物-微生物联合治理提供了可选菌株和理论依据.     

Biodegradation of geosmin in drinking water by novel bacteria isolated from biologically active carbon

Three strains of Gram-negative bacteria capable of removing geosmin from drinking water were isolated from biologically active carbon and identified to be Chryseobacterium sp., Sinorhizobium sp. and Stenotrophomonas sp. based on physio-biochemistry analysis and 16S rRNA gene sequence analysis. Removal e ciencies of 2 mg/L geosmin in mineral salts medium were 84.0%, 80.2% and 74.4% for Chryseobacterium sp., Sinorhizobium sp. and Stenotrophomonas sp., respectively, while removal e ciencies of 560 ng/L geosmin in filter influent were 84.8%, 82.3% and 82.5%, respectively. The biodegradation of geosmin was determined to be a pseudo first-order reaction, with rate constants at 2 mg/L and 560 ng/L being 0.097 and 0.086 day??1, 0.089 and 0.084 day??1, 0.074 and 0.098 day??1 for the above mentioned degraders, respectively. The biomass of culture in the presence of geosmin was much higher than that in the absence of geosmin.     

Isolation and identification of 3-bromocarbazole-degrading bacteria

In this study, a bacterial strain, CH-1, capable of degrading 3-bromocarbazole (3-BCZ) was isolated from a polluted soil. Based on its physio-biochemical characteristics and 16S rRNA genes, strain CH-1 was identified as a Stenotrophomonas sp. Strain CH-1 was able to degrade 70% of 50 mg/L 3-BCZ within 8 d at pH 7.0 and 30°C in mineral salt medium (MSM). During the process, the main intermediate metabolite was identified as (2E, 4Z)-6-(2-amino-5-bromophenyl)-2-hydroxy-6-oxhexa-2, 4-dienoic by gas (2E, 4Z)-6-(2-amino-5-bromophenyl)-2-hydroxy-6-oxhexa-2,4-dienoic via gas chromatograph-mass spectrometry (GC-MS) analysis. The metabolite disappeared after 14 d, suggesting that the metabolite can also be degraded by strain CH-1. 3-BCZ is a new persistent organic pollutant. This is the first report of the biodegradation of 3-BCZ. The results indicated that strain CH-1 may be a promising bacterial candidate for the bioremediation of environments polluted with polyhalogenated carbazoles (PHCs).     

Biodegradation of anthracene and phenanthrene by bacteria isolated from oil-contaminated soil of Bangladesh

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants entering into the environment through natural and anthropogenic activities. Owing to their toxicity to various life forms including humans, detoxification of PAHs is crucial to reduce their effects on cells. In this study, we have isolated two bacteria capable of degrading two common PAHs, anthracene and phenanthrene, from contaminated soil samples by using selective enrichment culture supplemented with test PAHs as the sole source of carbon and energy. The isolated bacteria were identified and affiliated as Pseudomonas aeruginosa strain KD and Stenotrophomonas maltophilia strain RC based on their 16s rRNA gene sequences. The degradation of anthracene and phenanthrene was estimated indirectly by measuring the decolourisation extent of a redox indicator, 2, 6-dichlorophenolindophenol, incorporated into PAH-supplemented mineral salt media. In the case of anthracene, ≥90% decolourisation was recorded at 20 and 48 days for P. aeruginosa and S. Maltophilia, respectively. On the other hand, ≥94% decolourisation was recorded at 56 and 52 days for P. aeruginosa and S. maltophilia, respectively during the utilisation of phenanthrene.     

一株微囊藻毒素降解菌的分离与鉴定

以水华蓝藻细胞中提取的微囊藻毒素为筛选物质,从太湖水华腐烂蓝藻中富集筛选出1株微囊藻毒素降解菌。该菌株革兰氏染色呈阴性,细胞细长杆状,菌落黄色,圆形,不透明,接触酶、氧化酶实验均呈阳性。16S rRNA基因序列的长度为1 416 bp(GenBank登录号为FJ976656)。系统发育树显示,该菌株与微嗜酸寡养单胞菌(Stenotrophomonas acidam-iniphila)的亲缘关系最近。通过菌株形态特征、生理生化特征和16S rRNA基因序列分析,将此菌株鉴定为微嗜酸寡养单胞菌,不同于已报道的微囊藻毒素降解菌属种。微囊藻毒素降解实验表明,该菌株5 d内将15.4 mg/L的微囊藻毒素完全降解,降解能力高于假单胞菌。     

微囊藻毒素-LR降解菌的筛选及降解特性研究

从上海市淀山湖表层水体中筛选分离出了1株降解微囊藻毒素-LR(MC-LR)的细菌并研究了其降解特性。根据细胞形态结构、生理生化特征及其16S rDNA基因序列分析,鉴定分离菌株DHU-28(GenBank序列登录号为HM047512)属嗜麦芽寡养单胞菌(Stenotrophomonas maltophilia)。微囊藻毒素降解实验结果表明,该菌株能在以MC-LR为唯一碳源、氮源的无机盐培养基中生长,6 d内可将初始质量浓度为15 mg/L的MC-LR降解为8.12 mg/L,降解效率达到45.9%。菌株DHU-28的最适生长温度是30℃,最适生长pH为7.0。酵母粉、蛋白胨、葡萄糖等营养物质可以明显促进菌株对MC-LR的降解效率,尤其是加入50 mg/L酵母粉后,6 d降解率达到63.2%。