Characteristic and role of chromosomal type II toxin-antitoxin systems locus in Enterococcus faecalis ATCC29212
Characteristic and role of chromosomal type II toxin-antitoxin systems locus in Enterococcus faecalis ATCC29212
复制标题
粪肠球菌ATCC29212染色体II型毒素-抗毒素系统位点的特征及作用
DOI：
10.1007/s12275-020-0079-3
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发表时间：
2020-10-23
影响因子：
3
通讯作者：
Liu，Guangzhi
中科院分区：
文献类型：
--
作者：
Li，Zhen;Shi，Chao;Liu，Guangzhi
革兰阳性菌粪肠球菌是目前引起医院感染的主要病原菌之一。粪肠球菌的生活方式主要依赖于其在恶劣环境条件下面对和生存的非凡能力。毒素-抗毒素(TA)系统与细菌在恶劣环境中的生长控制有关，但在肠球菌中报道很少。从粪肠球菌ATCC29212编码的10个TA系统中鉴定出3个功能II型TA系统。这些毒素基因具有与MazF(DR75_1948)和IMMA/IRRE家族金属内切酶(DR75_1673和DR75_2160)同源的保守结构域。毒素基因的过表达可抑制大肠杆菌的生长。而毒素DR75_1673不能抑制细菌生长，只有与抗毒素DR75_1672共表达时才有抑菌作用。DR75_1948-DR75_1949和DR75_160-DR75_2161能维持pLMO12102不稳定质粒在大肠杆菌中的稳定遗传。此外，这些TA在正常条件下以及在不同温度、抗生素、厌氧剂和H_2O_2培养条件下的转录水平存在显著差异。当DR752161基因被敲除后，突变菌株在高温和氧化应激条件下的生长受到限制。这些Tas基因座的实验特征可能有助于研究II型TA系统在肠球菌的生理和环境应激反应中的关键作用。
The Gram-positive bacterium Enterococcus faecalis is currently one of the major pathogens of nosocomial infections. The lifestyle of E. faecalis relies primarily on its remarkable capacity to face and survive in harsh environmental conditions. Toxin-antitoxin (TA) systems have been linked to the growth control of bacteria in response to adverse environments but have rarely been reported in Enterococcus. Three functional type II TA systems were identified among the 10 putative TA systems encoded by E. faecalis ATCC29212. These toxin genes have conserved domains homologous to MazF (DR75_1948) and ImmA/IrrE family metallo-endopeptidases (DR75_1673 and DR75_2160). Overexpression of toxin genes could inhibit the growth of Escherichia coli. However, the toxin DR75_1673 could not inhibit bacterial growth, and the bacteriostatic effect occurred only when it was coexpressed with the antitoxin DR75_1672. DR75_1948-DR75_1949 and DR75_160-DR75_2161 could maintain the stable inheritance of the unstable plasmid pLMO12102 in E. coli. Moreover, the transcription levels of these TAs showed significant differences when cultivated under normal conditions and with different temperatures, antibiotics, anaerobic agents and H2O2. When DR75_2161 was knocked out, the growth of the mutant strain at high temperature and oxidative stress was limited. The experimental characterization of these TAs loci might be helpful to investigate the key roles of type II TA systems in the physiology and environmental stress responses of Enterococcus.