SinR Controls Enterotoxin Expression in Bacillus thuringiensis Biofilms
SinR Controls Enterotoxin Expression in Bacillus thuringiensis Biofilms
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DOI：
10.1371/journal.pone.0087532
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发表时间：
2014-01-31
期刊：
影响因子：
3.7
通讯作者：
Gohar, Michel
中科院分区：
文献类型：
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作者：
Fagerlund, Annette;Dubois, Thomas;Gohar, Michel
昆虫病原体苏云金芽孢杆菌在各种条件下产生致密的生物膜。在此，我们报道过渡相调节因子 Spo0A、AbrB 和 SinR 控制苏云金芽孢杆菌的生物膜形成和游动运动，就像它们控制密切相关的腐生菌枯草芽孢杆菌的生物膜形成和集群运动一样。然而，微阵列分析表明，与枯草芽孢杆菌相反，在苏云金芽孢杆菌中，SinR不控制参与胞外多糖产生的eps操纵子，而是调节参与脂肽kurstakin生物合成的基因。这种脂肽是生物膜形成所必需的，之前已被证明对宿主尸体的生存（坏死性营养作用）很重要。微阵列分析还表明，SinR 调节子含有编码 Hbl 肠毒素的基因。转录融合测定、蛋白质印迹和溶血测定证实，SinR 与苏云金芽孢杆菌的主要毒力调节因子 PlcR 一起控制 Hbl 表达。我们发现，Hbl 在生物膜的一小部分亚群中以持续的方式表达，而几乎所有浮游群体都短暂表达 Hbl。 SinI 的编码基因（SinR 的拮抗剂）与 hbl 在同一生物膜亚群中表达，表明 hbl 转录异质性是 SinI 依赖性的。苏云金芽孢杆菌和蜡状芽孢杆菌是肠道细菌，它们可能在宿主肠上皮细胞内形成生物膜。因此，生物膜中产生的毒素可以直接传递到目标组织。
The entomopathogen Bacillus thuringiensis produces dense biofilms under various conditions. Here, we report that the transition phase regulators Spo0A, AbrB and SinR control biofilm formation and swimming motility in B. thuringiensis, just as they control biofilm formation and swarming motility in the closely related saprophyte species B. subtilis. However, microarray analysis indicated that in B. thuringiensis, in contrast to B. subtilis, SinR does not control an eps operon involved in exopolysaccharides production, but regulates genes involved in the biosynthesis of the lipopeptide kurstakin. This lipopeptide is required for biofilm formation and was previously shown to be important for survival in the host cadaver (necrotrophism). Microarray analysis also revealed that the SinR regulon contains genes coding for the Hbl enterotoxin. Transcriptional fusion assays, Western blots and hemolysis assays confirmed that SinR controls Hbl expression, together with PlcR, the main virulence regulator in B. thuringiensis. We show that Hbl is expressed in a sustained way in a small subpopulation of the biofilm, whereas almost all the planktonic population transiently expresses Hbl. The gene coding for SinI, an antagonist of SinR, is expressed in the same biofilm subpopulation as hbl, suggesting that hbl transcription heterogeneity is SinI-dependent. B. thuringiensis and B. cereus are enteric bacteria which possibly form biofilms lining the host intestinal epithelium. Toxins produced in biofilms could therefore be delivered directly to the target tissue.