Chukwudi Chinwe U, Good Liam
Department of Pathology and Infectious Diseases, Royal Veterinary College, University of London, UK; Department of Veterinary Pathology and Microbiology, University of Nigeria, Nsukka, Enugu State, Nigeria.
Department of Pathology and Infectious Diseases, Royal Veterinary College, University of London, UK.
Microb Pathog. 2015 Feb;79:70-9. doi: 10.1016/j.micpath.2015.01.009. Epub 2015 Jan 24.
The hok/sok locus is renowned for its plasmid stabilization effect via post-segregational killing of plasmid-free daughter cells. However, the function(s) of the chromosome-encoded loci, which are more abundant in pathogenic strains of a broad range of enteric bacteria, are yet to be understood. Also, the frequent occurrence of this toxin/antitoxin addiction system in multi-drug resistance plasmids suggests additional roles. In this study, the effects of the hok/sok locus on the growth of bacteria in stressful growth-limiting conditions such as high temperature and antibiotic burden were investigated using hok/sok plasmids. The results showed that the hok/sok locus prolonged the lag phase of host cell cultures, thereby enabling the cells to adapt, respond to the stress and eventually thrive in these growth-limiting conditions by increasing the growth rate at exponential phase. The hok/sok locus also enhanced the survival and growth of cells in low cell density cultures irrespective of unfavourable growth conditions, and may complement existing or defective SOS mechanism. In addition to the plasmid stabilization function, these effects would enhance the ability of pathogenic bacteria to establish infections and propagate the antibiotic resistance elements carried on these plasmids, thereby contributing to the virulence of such bacteria.
hok/sok位点因其通过对无质粒子代细胞进行后分离杀伤来实现质粒稳定作用而闻名。然而，染色体编码位点在多种肠道细菌的致病菌株中更为丰富，其功能尚不清楚。此外，这种毒素/抗毒素成瘾系统在多药耐药质粒中的频繁出现表明还有其他作用。在本研究中，使用hok/sok质粒研究了hok/sok位点在高温和抗生素负荷等应激性生长限制条件下对细菌生长的影响。结果表明，hok/sok位点延长了宿主细胞培养物的延迟期，从而使细胞能够适应、应对压力，并最终通过提高指数生长期的生长速率在这些生长限制条件下茁壮成长。hok/sok位点还增强了低细胞密度培养物中细胞的存活和生长，而不受不利生长条件的影响，并且可能补充现有的或有缺陷的SOS机制。除了质粒稳定功能外，这些作用将增强病原菌建立感染以及传播这些质粒携带的抗生素抗性元件的能力，从而导致此类细菌的毒力。
