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首页> 外文期刊>Advances in Bioscience and Biotechnology >Characteristics of dehalogenase from bacteria isolated from the Gut of Pond-reared Rohu (Labeo rohita) Juveniles in Myanmar
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Characteristics of dehalogenase from bacteria isolated from the Gut of Pond-reared Rohu (Labeo rohita) Juveniles in Myanmar

机译：缅甸池塘养的Rohu（Labeo rohita）幼虫肠道中分离出细菌的脱卤素酶特性

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Unwarranted accumulation of halogenated compounds in the rivers and streams has in recent years emerged due to the widespread use agricultural pesticides. The presence of these halogenated compounds in the water does not only suppress the immune system of fish but adversely induce serious morbidity and mortality among cultured stocks. Importantly, gradual accumulation of these compounds in the system of cultured and wild freshwater fish species cultured in ponds and floating net-cages in dams and rivers, respectively, poses some risks to humans, the end users. In this study, we attempted to isolate bacteria from the gut of pond-reared rohu (Labeo rohita) in Myanmar, screened the isolated bacteria for dehalogenase gene using molecular technique and tested the ability of these bacteria to degrade halogenated compounds in vitro. The eight bacterial strains studied were identified as Enterobacter mori strain MK- 121001, Enterobacter cloacae strains MK121003, MK-121004, MK121010, Ralstonia solanacearum strain 121002, Acinetobacter baumannii strain MK121007, Chromobacterium violaceum strain MK121009 and Pantoea vagans strain 121011. Only three bacterial strains (MK121002, MK121007 and MK121009) were capable of degrading 2,2-dichloropropionic acid (2,2-DCP) as the sole carbon source up to a final substrate concentration of 20 mM. Their mean growth doubling time ranging from 6-23 hours with the maximum of chloride ion released of 85%. PCR amplifica- tion with oligonucleotide primers designed from group I dehalogenase revealed the presence of deha- logenase genes in all isolates suggesting dehalogenase gene in strains 121001, 121003, 121004, 121010 and 121011 were silenced. In contrast, group II dehalogenase primers did not show any PCR amplification. These results suggest that MK121002, MK121007 and MK121009 only encode a group I dehalogenase and its non-stereoselectivity is in agreement with previoulsly described group I haloacid dehalogenase. The partial gene sequences were blasted but no significant sequence identity was observed. Therefore, it suggest the 2-haloacid dehalogenase of MK121002, MK12-1007 and MK121009 might be a novel group I 2-haloacid dehalogenase. The results indicated a broad distribution of dehalogenation genes in many micro- bial genomes that harbor dehalogenase(s) due to the exposure of the microorganisms to the naturally occurring or man-made halogenated compounds in the environmental systems. So far, microorganisms capable of producing dehalogenases were mainly isolated from soil and scarcely from aquatic animals and their environments. To the authors’ knowledge, this is the first report on the isolation of dehalogenase-producing bacteria from the gut of pond-reared freshwater fish, Labeo rohita, in Myanmar.
机译：由于农业农药的广泛使用，近年来出现了不必要的卤化物在河流和溪流中的积累。这些卤化物在水中的存在不仅会抑制鱼类的免疫系统，还会不利地导致养殖种群的严重发病和死亡。重要的是，这些化合物分别在池塘和水坝和河流中的养殖网箱和浮式网箱中养殖的和野生的淡水鱼系统中的逐步积累，对最终用户人类构成了一定的风险。在这项研究中，我们试图从缅甸池塘养殖的芜湖（Labeo rohita）的肠道中分离细菌，使用分子技术筛选分离的细菌的脱卤酶基因，并测试这些细菌在体外降解卤代化合物的能力。所研究的八种细菌菌株被鉴定为桑氏肠杆菌菌株MK- 121001，阴沟肠杆菌菌株MK121003，MK-121004，MK121010，青枯雷尔氏菌菌株121002，鲍曼不动杆菌菌株MK121007，紫杆菌细菌MK121009菌株和泛细菌变菌菌株121011。 （MK121002，MK121007和MK121009）能够降解2,2-二氯丙酸（2,2-DCP）作为唯一的碳源，直至最终底物浓度为20 mM。它们的平均生长倍增时间为6-23小时，最大释放的氯离子为85％。用I组脱卤酶设计的寡核苷酸引物进行PCR扩增，发现所有分离物中都存在脱卤酶基因，这表明121001、121003、121004、121010和121011菌株中的脱卤酶基因已沉默。相反，II组脱卤素酶引物未显示任何PCR扩增。这些结果表明，MK121002，MK121007和MK121009仅编码I组脱卤酶，其非立体选择性与之前所述的I组卤代酸脱卤酶一致。对部分基因序列进行blast处理，但未观察到明显的序列同一性。因此，这表明MK121002，MK12-1007和MK121009的2-卤代酸脱卤酶可能是一种新型的I组2-卤代酸脱卤酶。结果表明，由于微生物暴露于环境系统中天然存在的或人为的卤代化合物中，脱卤基因在具有脱卤酶的许多微生物基因组中分布广泛。迄今为止，能够产生脱卤酶的微生物主要是从土壤中分离出来的，很少是从水生动物及其环境中分离出来的。据作者所知，这是第一份关于从缅甸池塘饲养的淡水鱼Labeo rohita的肠道中分离出产生脱卤酶的细菌的报告。

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