蜡样芽孢杆菌ATCC14579毒力基因plcR缺失株的构建及其一般特性

蜡样芽孢杆菌是土壤中的优势菌,具有作为益生菌的潜在能力,同时它也是条件致病菌,能引起食物中毒等。蜡样芽孢杆菌的多种毒力因子受到多效性调控子（pleiotropic regulator,plcR）的调控,在其条件致病性作用中起着重要作用。真养产碱杆菌JMP34（Alcaligenes eutrophus）质粒上的2,4-二氯苯氧乙酸（2,4-dichlorophenoxyacetic acid,2,4-D）单加氧酶（tfdA）基因可以降解2,4-D。本研究利用同源重组技术使tfdA基因置换掉蜡样芽孢杆菌的plcR基因,构建了蜡样芽孢杆菌ATCC14579突变株B.cereus△plcRΩtf-dA,并对其毒性、一般生理生化特性进行分析。研究结果表明,突变株B.cereus△plcRΩtfdA的毒性显著减弱;生理生化实验结果显示突变株与野生株并没有明显区别,且突变株并没有表现出tfdA酶活性。所有的结果表明plcR控制着蜡样芽孢杆菌ATCC14579的致病性,同时剔除plcR并不破坏其酶系统。本研究为今后构建蜡样芽孢杆菌工程菌提供了新的思路和依据。

Construction and General Characteristics of the plcR Mutation in Bacillus cereus ATCC14579

Bacillus cereus possessing probiotic potential properties is a predominant bacteria in the soil.However,it is also an opportunistic pathogen that causes food poisoning.In Bacillus cereus,the pleiotropic regulator （PlcR）controls most known virulence factors and plays an important role in opportunistic pathogen.On the other hand,the 2,4-dichlorophenoxyacetic acid （2,4-D） monooxygenase （tfdA） gene of Alcaligenes eutrophus JMP34 can degrade 2,4-D.In this study,a plcR gene swapped for the tfdA mutant B.cereus△plcRΩtfdA was constructed by homologous recombination from Bacillus cereus ATCC14579,then we analyzed its virulence and common physiological and biochemical characteristics.The result showed that the toxicity was significantly reduced in the mutant strain B.cereus△plcRΩtfdA.At the same time,there was no significant difference between mutant and wild strain in physiological-biochemical experiments.Furthermore,the mutant strain was absent the activity of 2,4-D monooxygenase （tfdA）.Taken altogether,the results indicated that the pathogenicity of B.cereus strain ATCC14579 was controlled by plcR as well as didn＇t destroy its enzyme system.This research provides a new tactics and some bases for structuring an engineering bacterial strain of Bacillus cereus.