BACKGROUND Clostridium perfringens is a Gram-positive anaerobic pathogen that causes multiple diseases in humans and animals. C. perfringens lack flagella but have type IV pili (TFP) and can glide on agar surfaces. When C. perfringens bacteria are placed on surfaces, they become elongated, flexible and have TFP on their surface, traits not seen in liquid-grown cells. In addition, the main pilin in C. perfringens TFP, PilA2, undergoes differential post-translational modification when grown in liquid or on plates. To understand the mechanisms underlying these phenotypes, bacteria were grown in three types of liquid media and on agar plates with the same medium to compare gene expression using RNA-Seq. RESULTS Hundreds of genes were differentially expressed, including transcriptional regulatory protein-encoding genes and genes associated with TFP functions, which were higher on plates than in liquid. Transcript levels of TFP genes reflected the proportion of each protein predicted to reside in a TFP assembly complex. To measure differences in rates of translation, the Escherichia coli reporter gene gusA gene (encoding β-glucuronidase) was inserted into the chromosome downstream of TFP promoters and in-frame with the first gene of the operon. β-glucuronidase expression was then measured in cells grown in liquid or on plates. β-glucuronidase activity was proportional to mRNA levels in liquid-grown cells, but not plate-grown cells, suggesting significant levels of post-transcriptional regulation of these TFP-associated genes occurs when cells are grown on surfaces. CONCLUSIONS This study reveals insights into how a non-flagellated pathogenic rod-shaped bacterium senses and responds to growth on surfaces, including inducing transcriptional regulators and activating multiple post-transcriptional regulatory mechanisms associated with TFP functions.

中文翻译：

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当产气荚膜梭状芽孢杆菌在液体或表面上生长时，可以看到编码IV型菌毛相关蛋白的基因表达的变化。

背景技术产气荚膜梭菌是革兰氏阳性厌氧性病原体，其在人和动物中引起多种疾病。产气荚膜梭菌缺乏鞭毛，但具有IV型菌毛（TFP），可以在琼脂表面上滑动。当产气荚膜梭菌细菌放置在表面上时，它们会变得拉长，柔软并在其表面上具有TFP，这在液体生长的细胞中看不到。此外，产气荚膜梭菌TFP中的主要菌毛蛋白PilA2在液体或平板上生长时会经历不同的翻译后修饰。为了理解这些表型的潜在机制，细菌在三种类型的液体培养基中以及在具有相同培养基的琼脂平板上生长，以使用RNA-Seq比较基因表达。结果数百种基因差异表达，包括转录调节蛋白编码基因和与TFP功能相关的基因，在板上比在液体中高。TFP基因的转录水平反映了预计存在于TFP装配复合物中的每种蛋白质的比例。为了测量翻译速率的差异，将大肠杆菌报告基因gusA基因（编码β-葡糖醛酸糖苷酶）插入TFP启动子下游的染色体中，并与操纵子的第一个基因符合读框。然后在液体或平板上生长的细胞中测量β-葡萄糖醛酸苷酶的表达。β-葡萄糖醛酸苷酶活性与液体生长的细胞中的mRNA水平成正比，而与平板生长的细胞中的mRNA水平成正比，表明这些TFP相关基因的转录后调控水平很高，当细胞在表面生长时发生。