Zamani Isaac, Bouzari Majid, Emtiazi Giti, Fanaei Maryam
Department of Biology, Faculty of Science, University of Isfahan, Isfahan, IR Iran.
Jundishapur J Microbiol. 2015 Mar 21;8(3):e14965. doi: 10.5812/jjm.14965. eCollection 2015 Mar.
Halomethanes are toxic and carcinogenic chemicals, which are widely used in industry. Also they can be formed during water disinfection by chlorine. Biodegradation by methylotrophs is the most important way to remove these pollutants from the environment.
This study aimed to represent a simple and rapid method for quantitative study of halomethanes utilizing bacteria in drinking water and also a method to facilitate the biodegradation of these compounds in the environment compared to cometabolism.
Enumeration of chlorinated methane utilizing bacteria in drinking water was carried out by most probable number (MPN) method in two steps. First, the presence and the number of methylotroph bacteria were confirmed on methanol-containing medium. Then, utilization of dichloromethane was determined by measuring the released chloride after the addition of 0.04 mol/L of it to the growth medium. Also, the effect of nanosilver particles on biodegradation of multiple chlorinated methanes was studied by bacterial growth on Bushnell-Haas Broth containing chloroform (trichloromethane) that was treated with 0.2 ppm nanosilver.
Most probable number of methylotrophs and chlorinated methane utilizing bacteria in tested drinking water were 10 and 4 MPN Index/L, respectively. Chloroform treatment by nanosilver leads to dechlorination and the production of formaldehyde. The highest growth of bacteria and formic acid production were observed in the tubes containing 1% chloroform treated with nanosilver.
By combining the two tests, a rapid approach to estimation of most probable number of chlorinated methane utilizing bacteria is introduced. Treatment by nanosilver particles was resulted in the easier and faster biodegradation of chloroform by bacteria. Thus, degradation of these chlorinated compounds is more efficient compared to cometabolism.
卤代甲烷是有毒且致癌的化学物质，在工业中广泛使用。它们也可在氯消毒水的过程中形成。甲基营养菌的生物降解是从环境中去除这些污染物的最重要方式。
本研究旨在提出一种简单快速的方法，用于定量研究饮用水中利用细菌的卤代甲烷，以及一种与共代谢相比促进这些化合物在环境中生物降解的方法。
采用两步最可能数（MPN）法对饮用水中利用氯甲烷的细菌进行计数。首先，在含甲醇的培养基上确认甲基营养菌的存在和数量。然后，通过向生长培养基中添加0.04 mol/L二氯甲烷后测量释放的氯离子来确定其利用情况。此外，通过在含有经0.2 ppm纳米银处理的氯仿（三氯甲烷）的布什内尔-哈斯肉汤中培养细菌，研究了纳米银颗粒对多种氯代甲烷生物降解的影响。
受试饮用水中甲基营养菌和利用氯甲烷的细菌的最可能数分别为10和4 MPN指数/升。纳米银处理氯仿导致脱氯并产生甲醛。在含有1%经纳米银处理的氯仿的试管中观察到细菌生长和甲酸产生最高。
通过结合这两种测试，引入了一种快速估算利用氯甲烷细菌最可能数的方法。纳米银颗粒处理使细菌对氯仿的生物降解更容易、更快。因此，与共代谢相比，这些氯代化合物的降解更有效。
