Function of arsATorf7orf8 of Bacillus sp. CDB3 in arsenic resistance

Bacillus sp. CDB3 isolated from an arsenic contaminated cattledip site possesses an uncommon arsenic resistance (ars) operon bearing eight genes in the order of arsRYCDATorf7orf8. We investigated the functions of arsA, arsT, orf7 and orf8 in arsenic resistance using a plasmid-based gene knockout approach in the ars genedeficient Escherichia coli strain AW3110. The CDB3 arsA genewas shown to play a significant role in resistance, suggesting that the encoded ArsA may couplewith the arsenite transporter, forming an ArsAY complex that can enhance arsenite extrusion efficiency. Thedisruption of either arsT or orf7was not observed to affect arsenic resistance in the heterologous E. coli host, but their involvement in arsenic resistance can not be excluded. The orf8 gene is predicted to encode a putativedual-specificity protein phosphatasewhich also shares certain homology to arsenate reductases. The function loss of orf8 resulted in a remarkabledecrease in resistance to arsenate, though not arsenite. To examine if this effectwasdue to the reduction of arsenate by orf8, the arsC genewithin the 8-gene operonwasdisrupted. The resulting abolishment of arsenate resistance suggests that the involvement of orf8 in arsenic resistance is not via reductase activity.     

生物炭对热带地区辣椒种植土壤N2O排放及其功能基因的影响

生物炭具有一定的增产和减少N₂O排放效果,但关于其相关氮循环微生物作用的动态变化过程了解较少.为探明热带地区生物炭的增产减排效应潜力及相关微生物动态作用机制,通过辣椒盆栽试验对比添加生物炭(B)、常规施肥(CON)和不施氮(CK)处理对辣椒产量、氧化亚氮(N₂O)的排放及相关功能基因丰度的影响.结果表明,CON处理产量高于CK处理;与CON处理相比,生物炭显著增加辣椒产量18.0%(P<0.05),添加生物炭在辣椒生长的大部分时期增加土壤NH⁺₄-N和NO^-₃-N含量;在辣椒的生长周期内,相比CON处理,生物炭处理显著减少土壤N₂O累积排放量18.3%(P<0.05).N₂O排放通量与氨氧化古菌(AOA)和氨氧化细菌(AOB)的amoA基因丰度呈极显著负相关(P<0.01);与nosZ基因丰度呈显著负相关(P<0.05),表明N₂O排放可能主要来自反硝化过程;在辣椒生...     

水位波动和氮浓度变化对氮转化功能基因丰度的影响

为探索浅层地下水氮浓度及水位波动对土壤剖面中氮转化功能基因丰度的影响,以洱海近岸农田原状土壤剖面为对象,研究了模拟常规氮浓度的浅层地下水进行水位波动(SND)和持续淹水(SNF),以及无氮浓度的浅层地下水位波动(0ND)后土壤剖面氮浓度和氮转化功能基因丰度的变化,探讨了土壤因子与功能基因丰度的关系。结果表明:SNF、SND和0ND处理较试验前土壤剖面中溶解性总氮(TDN)浓度分别降低了44%、21%和30%,NO₃⁻-N浓度分别降低了55%、28%和38%。同时,0ND和SNF处理较SND处理土壤剖面中反硝化功能基因丰度分别降低20%和1%,厌氧氨氧化功能基因丰度则分别增加68%和7%,硝化功能基因丰度分别降低34%和增加23%,土壤含水率(MC)、NH₄⁺-N、NO₃⁻-N和TDN均为功能基因丰度变化的重要驱动因子。土壤剖面持续淹水会显著降低溶解性氮浓度,浅层地下水波动及水中氮浓度引起的土壤剖面干湿交替和氮浓度变化是氮转化功能基因丰度变化的主要驱动力。     

低温下磁性载体MBBR系统微生物群落特征和功能预测分析

为阐明低温下磁性载体对移动床生物膜反应器(MBBR)处理能力的影响,探究了反应器内生物膜的微生物多样性、群落结构、功能特征和氮代谢通路.结果表明,与商用载体反应器(对照组)相比,磁性载体反应器具有更高的污染物去除率,其对NH⁺₄-N和TN的平均去除率分别提高了16.2%和12.1%.Illumina高通量测序结果显示,磁性载体生物膜的微生物多样性和丰富度更高.由于不同微生物的磁化率不同,导致两种载体生物膜微生物群落结构存在显著差异.磁性载体生物膜中硝化菌属(如：Nitrosomonas、Nitrospira)和反硝化菌属(如：Sphaerotilus、Zoogloea)的相对丰度显著增多.PICRUSt2功能预测分析显示,磁性载体生物膜的整体基因功能表达水平更高,在信号传导机制和细胞内运输、分泌和囊泡运输等方面优势更明显.此外,大多数与氮代谢相关基因在磁性载体生物膜中丰度更高,如涉及硝化过程的基因amo、hao和反硝化过程基因nap、nor等,使得生物膜的低温脱氮潜力增强.以上结果从微观生物学角度更好地解释了反应器处理能力的差异,为磁性载体强...     

Long-term impacts of graphene oxide and Ag nanoparticles on anammox process: Performance, microbial community and toxic mechanism

The increasing application of engineered nanoparticles (NPs) has posed an emerging challenge to constructed wetland wastewater treatment. The performance, microbial community and toxic mechanism of anammox-based unplanted subsurface-flow constructed wetlands (USFCWs) were investigated under the long-term exposure of different graphene oxides (GOs) and Ag NP concentrations. Results showed that the addition of GO could promote TN removal, manifesting as function anammox bacteria C. Anammoxoglobus having a relative high abundance, for GO did not cause significant damage to the cell integrity though there was an increase in ROS concentrations. TN removal would not be obviously affected under exposure of 1?mg/L Ag NPs, for the function gene related to cell biogenesis and repair was up-regulated; while the addition of 10?mg/L Ag NPs would have an inhibiting effect on TN removal in the USFCWs, for the disappearance of some species having anammox ability. Key enzymes of anammox process (NIR and HDH) decreased to some extent under GO and Ag NP exposure, and function gene of defense mechanisms had an increase trend in samples.     

三岔湖沉积物中葡萄糖脱氢酶gcd基因的多样性及其与环境因子的关系

为了研究沉积物中葡萄糖脱氢酶gcd基因多样性及其与环境因子的关系,揭示对水体富营养化有重要影响的微生物类群,分别于2017年的春季和秋季对三岔湖沉积物及其表层上覆水采样,对沉积物基因组DNA的gcd基因进行高通量测序,分析gcd基因多样性和群落结构特征,探讨其与环境因子之间的关系.结果表明:①12个样品共得到219 778条有效序列,分属于6门、9纲、15目、29科、46属、610个OTUs,主要来源于变形菌门（25.10%~98.85%）、酸杆菌门（0~3.99%）.②gcd基因序列系统发育树分为两支,四亚支,基因序列主要归属于根瘤菌目、伯克氏菌目、海洋螺菌目、假单胞菌目、酸杆菌目.③gcd基因的生物多样性大小为春季>秋季,湖中心>湖坝>湖尾;在gcd基因细菌群落组成上,季节性变化对L1、L2、L3、L5采样点影响较小,而对L4和L6采样点影响较大.④gcd基因的生物多样性与ρ（DO）、w（TP）、w（HCl-P）、ρ（DTP）显著相关,gcd基因的OTU组成和分布与ρ（DO）、ρ（DTP）显著相关.研究显示,三岔湖水体沉积物中的gcd基因具有较高的生物多样性,组成和分布呈现异质性,对ρ（DTP）具有重要影响作用.      

一株降解微囊藻毒素的缺陷短波单胞菌的分离鉴定及降解特性研究

从太湖水华腐烂蓝藻中筛选出一株能够降解MC-LR的细菌,将其编号为Q3.经形态、生理生化及16S rRNA基因序列分析鉴定为缺陷短波单胞菌(Brevundimonas diminuta).研究发现,在实验条件下该菌能以MC-LR为唯一碳源和氮源生长;7 d内可将初始浓度为0.96 mg·L-1的MC-LR降解为0.37 mg·L-1,降解效率达到61.5%.同时,本研究首次发现缺陷短波单胞菌能够降解藻毒素,并且在此菌种中扩增出了降解过程的关键基因mlr A,推测该菌可能与已报道的Sphingomonas sp.ACM-3962等菌具有相同的降解机制.     

多聚磷酸盐激酶基因在污水生物除磷中的功能

为验证多聚磷酸盐激酶基因(ppk)在污水生物除磷中的功能.采用Red敲除系统,以p KD4质粒为模板,设计同源短臂,扩增外源线性DNA片段,将外源线性DNA片段电转化整合入已导入p KD46的大肠杆菌ATCC25922野生型菌株.获得重组菌E.coli/ppk~-Kan~+.将p CP20导入大肠杆菌E.coli/ppk~-Kan~+以消除卡那霉素抗性基因,通过负抗性筛选及正反向引物验证,构建无抗生素抗性的ppk基因缺失工程菌株E.coli/ppk~-Kan~-.比较工程菌株和野生型菌株的生长特性,并比较两者在缺磷诱导/富磷及多次厌氧/好氧诱导条件下的除磷性能.结果表明采用Red重组系统,通过无痕敲除,成功构建了大肠杆菌ppk基因缺失菌株E.coli/ppk~-Kan~-.敲除后的工程菌株和野生型菌株生长整体没有差异,但是4 h前对数期工程菌株生长快于野生型菌株,8 h后稳定期工程菌株生长慢于野生型菌株,表明ppk影响菌体的生长;缺磷诱导/富磷条件下,工程菌株并未表现出因ppk缺失而影响其除磷能力;经过5次厌氧/好氧诱导,两菌菌体含磷量保持在1%~2%,没有因诱导次数的增加而表现出菌体含磷量增加的趋势,也未发现厌氧有PHB好氧有聚磷颗粒生成,表明ppk基因的缺失并没有引起菌体除磷能力的下降.ppk并未表现出明显的与污水生物除磷相关的功能.     

Evaluation of bacterial pathogen diversity, abundance and health risks in urban recreational water by amplicon next-generation sequencing and quantitative PCR

The microbial quality of urban recreational water is of great concern to public health.The monitoring of indicator organisms and several pathogens alone is not sufficient to accurately and comprehensively identify microbial risks.To assess the levels of bacterial pathogens and health risks in urban recreational water,we analyzed pathogen diversity and quantified four pathogens in 46 water samples collected from waterbodies in Beijing Olympic Forest Park in one year.The pathogen diversity revealed by 16 S r RNA gene targeted next-generation sequencing(NGS) showed that 16 of 40 genera and 13 of 76 reference species were present.The most abundant species were Acinetobacter johnsonii,Mycobacterium avium and Aeromonas spp.Quantitative polymerase chain reaction(q PCR) of Escherichia coli(uid A),Aeromonas(aer A),M.avium(16S r RNA),Pseudomonas aeruginosa(oaa) and Salmonella(inv A) showed that the aer A genes were the most abundant,occurring in all samples with concentrations of 10~(4–6) genome copies/100 m L,followed by oaa,inv A and M.avium.In total,34.8% of the samples harbored all genes,indicating the prevalence of these pathogens in this recreational waterbody.Based on the q PCR results,a quantitative microbial risk assessment(QMRA) showed that the annual infection risks of Salmonella,M.avium and P.aeruginosa in five activities were mostly greater than the U.S.EPA risk limit for recreational contacts,and children playing with water may be exposed to the greatest infection risk.Our findings provide a comprehensive understanding of bacterial pathogen diversity and pathogen abundance in urban recreational water by applying both NGS and q PCR.     

磺胺抗性消长与堆肥进程的交互特征

基于添加和不添加磺胺药[m(磺胺二甲嘧啶SM2)∶m(磺胺-6-甲氧嘧啶SMM)=1∶1]的好氧堆肥试验,分析堆肥过程中鸡粪理化性质、微生物群落代谢特征、磺胺抗生素以及5种抗性基因变化,探明磺胺抗性消长与堆肥过程的交互特征.结果表明,磺胺药添加抑制了堆肥基础呼吸,延长了堆体达到高温的时间,减缓了养分转化速度,显著影响堆肥中期微生物群落结构特征.鸡粪中SMM和SM2在堆肥14 d内即可完全降解,且SMM降解速率高于SM2.随堆肥进行,sul1和sul2呈先下降后轻微回升的趋势,磺胺药添加对sul1和Int I1丰度无明显提高作用,但可促进sul2扩散.堆肥过程中,tet Q和tet W变化与磺胺抗性基因不同,但磺胺药添加亦增加tet Q和tet W相对丰度.冗余分析结果显示,温度与sul1、sul2和Int I1明显负相关,与tet Q和tet W无明显相关性;5种抗性基因相对丰度均与碳氮比和硝态氮含量负相关,与p H、含水率和铵态氮含量正相关.