近日，国际学术期刊PLoS Pathogens发表了中国科学技术大学生命科学学院孙宝林研究组的研究成果。该研究揭示了金黄色葡萄球菌可选择性σ因子σH参与调控原噬菌体在宿主基因组上整合和外切的过程。
原噬菌体是病原菌重要的可移动基因元件之一，常携带有大量毒力相关基因，直接影响了病原菌的致病力强弱。金黄色葡萄球菌是临床感染和食品工业污染最重要的病原菌之一。孙宝林研究组的博士生陶亮和吴晓倩通过对金黄色葡萄球菌原噬菌体的序列分析，发现了其整合酶启动子区域存在一段保守序列，该序列受宿主可选择性σ因子σH的识别和调控，进而影响了原噬菌体在基因组上的整合和剪切频率。
宿主因子调控原噬菌体的整合和外切过程展示了一种新的病原菌宿主影响噬菌体溶源性的策略。该研究有助于深入理解金黄色葡萄球菌可移动基因元件相关致病因子的转移和表达规律。
原文出处：
PLoS Pathog doi:10.1371/journal.ppat.1000888
Alternative Sigma Factor σH Modulates Prophage Integration and Excision in Staphylococcus aureus
Liang Tao#, Xiaoqian Wu#, Baolin Sun*
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China
The prophage is one of the most important components of variable regions in bacterial genomes. Some prophages carry additional genes that may enhance the toxicity and survival ability of their host bacteria. This phenomenon is predominant in Staphylococcus aureus, a very common human pathogen. Bioinformatics analysis of several staphylococcal prophages revealed a highly conserved 40-bp untranslated region upstream of the int gene. A small transcript encoding phage integrase was identified to be initiated from the region, demonstrating that the untranslated region contained a promoter for int. No typical recognition sequence for either σA or σB was identified in the 40-bp region. Experiments both in vitro and in vivo demonstrated that σH recognized the promoter and directed transcription. Genetic deletion of sigH altered the int expression, and subsequently, the excision proportion of prophage DNAs. Phage assays further showed that sigH affected the ability of spontaneous lysis and lysogenization in S. aureus, suggesting that sigH plays a role in stabilizing the lysogenic state. These findings revealed a novel mechanism of prophage integration specifically regulated by a host-source alternative sigma factor. This mechanism suggests a co-evolution strategy of staphylococcal prophages and their host bacteria.
