Synergistic Activity of Mobile Genetic Element Defences in Streptococcus pneumoniae

Genes

Christophe Fraser¹  MarcoR. Oggioni²  MinJung Kwun³  NicholasJ. Croucher³  StephenD. Bentley⁴ 

[1] Big Data Institute, Nuffield Department of Medicine, Old Road Campus, University of Oxford, Oxford OX3 7LF, UK;Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK;MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, St. Mary’s Campus, Imperial College London, London W2 1PG, UK;Pathogens and Microbes, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SA, UK;

关键词: Streptococcus pneumoniae;    pneumococcus;    restriction-modification system;    phase variation;    transformation;    recombination;    mobile genetic elements;    prophage;   

DOI  :  10.3390/genes10090707

来源: DOAJ

【 摘 要 】

A diverse set of mobile genetic elements (MGEs) transmit between Streptococcus pneumoniae cells, but many isolates remain uninfected. The best-characterised defences against horizontal transmission of MGEs are restriction-modification systems (RMSs), of which there are two phase-variable examples in S. pneumoniae. Additionally, the transformation machinery has been proposed to limit vertical transmission of chromosomally integrated MGEs. This work describes how these mechanisms can act in concert. Experimental data demonstrate RMS phase variation occurs at a sub-maximal rate. Simulations suggest this may be optimal if MGEs are sometimes vertically inherited, as it reduces the probability that an infected cell will switch between RMS variants while the MGE is invading the population, and thereby undermine the restriction barrier. Such vertically inherited MGEs can be deleted by transformation. The lack of between-strain transformation hotspots at known prophage att sites suggests transformation cannot remove an MGE from a strain in which it is fixed. However, simulations confirmed that transformation was nevertheless effective at preventing the spread of MGEs into a previously uninfected cell population, if a recombination barrier existed between co-colonising strains. Further simulations combining these effects of phase variable RMSs and transformation found they synergistically inhibited MGEs spreading, through limiting both vertical and horizontal transmission.

【 授权许可】

Unknown