Smith Daniel, Crowley David E
Department of Environmental Sciences, University of California, Riverside, CA 92521, USA.
FEMS Microbiol Ecol. 2006 Nov;58(2):271-7. doi: 10.1111/j.1574-6941.2006.00168.x.
Bacterial communities that cooperatively degrade atrazine commonly consist of diverse species in which the genes for atrazine dechlorination and dealkylation are variously distributed among different species. Normally, the first step in degradation of atrazine involves dechlorination mediated by atzA, followed by stepwise dealkylation to yield either N-ethylammelide or N-isopropylammelide. As the liberated alkylamine moieties are constituents of many organic molecules other than atrazine, it is possible that a large number of alkylamine-degrading bacteria other than those previously described might contribute to this key step in atrazine degradation. To examine this hypothesis, we isolated 82 bacterial strains from soil by plating soil water extracts on agar media with ethylamine as a sole carbon source. Among the relatively large number of isolates, only 3 were able to degrade N-ethylammelide, and in each case were shown to carry the atzB gene and atzC genes. The isolates, identified as Rhizobium leguminosarum, Flavobacterium sp., and Arthrobacter sp., were all readily substituted into an atrazine-degrading consortium to carry out N-ethylammelide degradation. The distribution of these genes among many different species in the soil microbial population suggests that these genes are highly mobile and over time may lead to generation of various atrazine-degrading consortia.
协同降解阿特拉津的细菌群落通常由多种不同的物种组成，其中阿特拉津脱氯和脱烷基化的基因在不同物种中呈多样化分布。通常，阿特拉津降解的第一步是由atzA介导的脱氯反应，随后是逐步脱烷基化反应，生成N-乙基酰胺或N-异丙基酰胺。由于释放出的烷基胺部分是除阿特拉津之外的许多有机分子的组成部分，因此除了先前描述的那些细菌外，可能有大量降解烷基胺的细菌会参与阿特拉津降解的这一关键步骤。为了验证这一假设，我们通过将土壤水提取物接种在以乙胺作为唯一碳源的琼脂培养基上，从土壤中分离出了82株细菌菌株。在数量相对较多的分离菌株中，只有3株能够降解N-乙基酰胺，并且在每种情况下都显示携带atzB基因和atzC基因。这些被鉴定为豆科根瘤菌、黄杆菌属和节杆菌属的分离菌株，都很容易被引入到一个降解阿特拉津的菌群中以进行N-乙基酰胺的降解。这些基因在土壤微生物种群中许多不同物种间的分布表明，这些基因具有高度的流动性，随着时间的推移可能会导致各种降解阿特拉津的菌群的产生。
