UV light tolerance and reactivation potential of tetracycline-resistant bacteria from secondary effluents of a wastewater treatment plant

Tetracycline-resistant bacteria (TRB) are of concern as emerging microbial contaminants in reclaimed water. To understand the effects of UV disinfection on TRB, both inactivation and reactivation profiles of TRB, as well as 16 tetracycline-resistant isolates from secondary effluent, were characterized in this study. The inactivation ratio of TRB was significantly lower (3.0-log) than that of heterotrophic bacteria (> 4.0-log) in the secondary effluent. Additionally, the proportion of TRB significantly increased from 1.65% to 15.51% under 20 mJ/cm² ultraviolet (UV) exposure. The inactivation rates of tetracycline-resistant isolates ranged from 0.57/s to 1.04/s, of which tetracycline-resistant Enterobacter-1 was the most tolerant to UV light. The reactivation of TRB, tetracycline-resistant isolated strains, as well as heterotrophic bacteria commonly occurred in the secondary effluent even after 20 mJ/cm² UV exposure. The colony forming ability of TRB and heterotrophic bacteria reached 3.2-log and 3.0-log under 20 mJ/cm² UV exposure after 22 hr incubation. The final inactivation ratio of tetracycline-resistant Enterobacter-1 was 1.18-log under 20 mJ/cm² UV exposure after 22 hr incubation, which is similar to those of TRB (1.18-log) and heterotrophic bacteria (1.19-log). The increased proportion of TRB and the reactivation of tetracycline-resistant enterobacteria in reclaimed water could induce a microbial health risk during wastewater reuse.     

固定化SRB处理低浓度含铬废水

主要选用海藻酸钠和聚乙烯醇等为包埋剂,采用包埋法对SRB细菌进行固定化,并且以固定化小球对铬的去除率为主要参考指标,从失重率、传质性等方面综合考虑,通过正交试验确定固定化小球的最佳配比,同时采用这种新型的固定化小球处理含低浓度铬废水。试验结果表明,固定化SRB小球的最佳包埋条件为:聚乙烯醇8%,二氧化硅2%,海藻酸钠0.2%,活性炭3%,菌液含量30%,饱和硼酸中氯化钙2%,交联时间24 h。固定化小球处理低浓度含铬废水的最佳条件为:p H为6,温度为30℃,初始铬离子浓度为1 mg/L,在250 min内小球表面的活性位点趋于饱和,此时Cr去除率为92%。     

反硝化聚磷菌的筛选及脱氮除磷特性

为进一步研究反硝化聚磷菌的机理和性能,对经过SBR反应器富集驯化后的污泥进行实验研究。采用吸磷实验、硝酸盐还原产气实验、革兰氏染色及异染颗粒染色等方法,筛选得到N10、N17和N20 3株菌株;经过16S r DNA的测序鉴定,建立系统发育树,确定3株菌株均为气单胞菌属。绘制3株菌株的生长曲线,并进行厌氧/缺氧和厌氧/好氧静态实验,发现N10和N17菌株在两组实验中均具有较好的脱氮除磷效果,O2和硝酸盐均可作为电子受体;N20菌株仅在厌氧/缺氧实验中表现出脱氮除磷效果,仅可利用硝酸盐作为电子受体。     

Comparison of nitroethane, 2-nitro-1-propanol,lauric acid,Lauricidin® and the Hawaiian marine algae,Chaetoceros, for potential broad-spectrum control of anaerobically grown lactic acid bacteria

The gastrointestinal tract of bovines often contains bacteria that contribute to disorders of the rumen, and may also contain foodborne or opportunistic human pathogens as well as bacteria capable of causing mastitis in cows. Thus there is a need to develop broad-spectrum therapies that are effective while not leading to unacceptably long antibiotic withdrawal times. The effects of the CH₄-inhibitors nitroethane (2 mg/mL), 2-nitro-1-propanol (2 mg/mL), lauric acid (5 mg/mL), the commercial product Lauricidin® (5 mg/mL), and a finely ground product of the Hawaiian marine algae, Chaetoceros (10 mg/mL), were compared in pure cultures of Streptococcus agalactia, Enterococcus faecium, Streptococcus bovis, and in a mixed lactic acid rumen bacterial culture. Lauricidin® and lauric acid exhibited the most bactericidal acidity against all bacteria. These results suggest potential animal health benefits from supplementing cattle diets with lauric acid or Lauricidin® to improve the health of the rumen and help prevent shedding of human pathogens.     

两株菲降解菌株的特性及其系统发育分析

从石油污染土壤中分离到两株可以菲为唯一碳源的细菌菌株,经形态和生理生化特性分析,脂肪酸含量分析和16S rDNA序列同源性鉴定, 两菌均属鞘氨醇单胞菌属(Sphingomonas),菌株ZX4为少动鞘氨醇单胞菌(Sphingomonas paucimobilis),而菌株EVA17与该属内已知菌的序列同源性在93%~98%之间,推测可能为一新种.两菌株在不同碳源培养基上的生长曲线表明菲对细菌生长有明显的延滞作用.菌株EVA17全细胞蛋白质电泳图谱揭示该细菌在菲诱导下可出现诱导性蛋白,推测可能为一些解毒酶或降解酶.菲降解细菌在以结晶态菲为碳源时生长速率明显低于以粉末态菲为碳源时的生长速率,表明细菌与菲间的接触面积是限制其利用菲的一个重要因素.分离菌株谷胱甘肽S-转移酶(GST酶)具有可与1-氯-2,4-二硝基苯(CDNB)结合的活性.添加表面活性剂吐温-80可促进细菌对菲的利用.     

生物法废气净化专用微生物菌种及其作用

用气相培育驯化法培养获得废气净化专用菌种,由其挂膜制作的生物膜填料塔对废气中甲苯进行净化,实验结果表明,气相培养法所得菌种对甲苯的净化性能明显优于液相培养法所得菌种.生物膜通过吸附-生物降解作用过程净化气相中的甲苯,使针对挥发性有机废气生物净化过程提出的吸附-生物膜动力学理论的依据得到了验证.     

亚硝酸盐为电子受体反硝化除磷工艺的可行性

采用序批式反应器(SBR),以亚硝酸盐为电子受体,探讨了厌氧/缺氧条件下反硝化除磷工艺的可行性,并通过间歇实验考察了亚硝酸盐浓度、进水COD浓度和进水pH值对反硝化除磷工艺的影响.结果表明,亚硝酸盐作为电子受体的同步脱氮除磷过程是完全可以实现的,控制NO₂^--N浓度为35±5mg/L、厌氧段进水pH值为8.0±0.1,缺氧段进水pH值为7.2±0.1、COD浓度为400mg/L时,反硝化除磷效果最佳.     

氯代苯类化合物对江水细菌的毒性及QSAR研究

采用细菌生长抑制实验,测定了18种氯苯类化合物对长江水中混合细菌的毒性,得到24 hIC₅₀值,-1gIC₅₀为3.65～4.32,其中,毒性最弱的是氯苯,毒性最强的是1,2,4-三氯苯.选用分子连接性指数法对毒性数据进行定量结构活性关系(QSAR)研究.结果表明,氯苯类化合物对江水细菌的毒性与苯环上取代基的种类、数目和位置有关,价分子连接性指数0XV和7X_CHV能够很好地描述氯苯类化合物对江水细菌的毒性.方程-1gIC₅₀=0.8390XV-25.3727X_CHV+0.802的稳健性很好,该模型的预测值与毒性实测值之间的相关系数达0.948.      

附生假单胞菌信号分子对铜绿微囊藻磷代谢的影响

通过在不同的磷浓度和细胞浓度的铜绿微囊藻培养液中添加附生假单胞菌信号分子,研究了附生假单胞菌信号分子对铜绿微囊藻生长及磷代谢的影响．结果表明,与对照相比,附生假单胞菌信号分子能抑制高浓度铜绿微囊藻的生长,促使低浓度铜绿微囊藻衰亡,并可以促进在衰亡期藻细胞内磷的积累．附生假单胞菌的信号分子可以在附生假单胞菌-铜绿微囊藻种间起作用,影响铜绿微囊藻的生长和磷代谢。     

降解菌对堆肥中多环芳烃降解作用的研究

通过在堆肥中加入经过驯化的降解菌这种土壤有机污染生物修复技术 ,对堆肥中多环芳烃的浓度变化进行监测 ,从而了解降解菌对堆肥中多环芳烃的降解作用。实验结果表明 ,降解菌的加入能明显地提高多环芳烃的降解率 ,本次实验中 ,菲、芴的去除率提高了 2 5 %左右 ,芘的去除率提高了约 4 5 %。