Editing Streptococcus pneumoniae (section)

===Transformation===
Natural bacterial transformation involves the transfer of DNA from one bacterium to another through the surrounding medium. Transformation is a complex developmental process requiring [[energy]] and is dependent on expression of numerous genes. In ''S. pneumoniae'', at least 23 genes are required for transformation. For a bacterium to bind, take up, and recombine [[exogenous DNA]] into its [[chromosome]], it must enter a special physiological state called [[natural competence|competence]].<ref>Bernstein H, Bernstein C, Michod RE. Sex in microbial pathogens. Infect Genet Evol. 2018 Jan;57:8-25. doi: 10.1016/j.meegid.2017.10.024. Epub 2017 Oct 27. PMID 29111273</ref>
Competence in ''S. pneumoniae'' is induced by DNA-damaging agents such as [[mitomycin C]], [[fluoroquinolone]] [[antibiotic]]s ([[norfloxacin]], [[levofloxacin]] and [[moxifloxacin]]), and [[topoisomerase inhibitor]]s.<ref>{{cite journal |vauthors=Claverys JP, Prudhomme M, Martin B |title=Induction of competence regulons as a general response to stress in gram-positive bacteria |journal=Annu. Rev. Microbiol. |volume=60 |pages=451–75 |year=2006 |pmid=16771651 |doi=10.1146/annurev.micro.60.080805.142139 }}</ref> Transformation protects ''S. pneumoniae'' against the bactericidal effect of mitomycin C.<ref>{{cite journal |vauthors=Engelmoer DJ, Rozen DE |title=Competence increases survival during stress in Streptococcus pneumoniae |journal=Evolution |volume=65 |issue=12 |pages=3475–85 |date=December 2011 |pmid=22133219 |doi=10.1111/j.1558-5646.2011.01402.x |s2cid=24634666 |doi-access=free }}</ref>  Michod et al.<ref>{{cite journal |vauthors=Michod RE, Bernstein H, Nedelcu AM |title=Adaptive value of sex in microbial pathogens |journal=Infect. Genet. Evol. |volume=8 |issue=3 |pages=267–85 |date=May 2008 |pmid=18295550 |doi=10.1016/j.meegid.2008.01.002 |bibcode=2008InfGE...8..267M |url=http://www.hummingbirds.arizona.edu/Faculty/Michod/Downloads/IGE%20review%20sex.pdf}}</ref> summarized evidence that induction of competence in ''S. pneumoniae'' is associated with increased resistance to [[oxidative stress]] and increased expression of the RecA protein, a key component of the [[recombinational repair]] machinery for removing [[DNA damage]]. On the basis of these findings, they suggested that transformation is an adaptation for repairing oxidative DNA damage. ''S. pneumoniae'' infection stimulates [[granulocyte|polymorphonuclear leukocytes]] (granulocytes) to produce an oxidative burst that is potentially lethal to the bacteria. The ability of ''S. pneumoniae'' to repair oxidative DNA damage in its genome caused by this host defense likely contributes to the pathogen's virulence. Consistent with this premise, Li et al.<ref name="pmid27068094">{{cite journal |vauthors=Li G, Liang Z, Wang X, Yang Y, Shao Z, Li M, Ma Y, Qu F, Morrison DA, Zhang JR |title=Addiction of Hypertransformable Pneumococcal Isolates to Natural Transformation for In Vivo Fitness and Virulence |journal=Infect. Immun. |volume=84 |issue=6 |pages=1887–901 |year=2016 |pmid=27068094 |doi=10.1128/IAI.00097-16 |pmc=4907133}}</ref> reported that, among different highly transformable ''S. pneumoniae'' isolates, nasal colonization fitness and virulence (lung infectivity) depend on an intact competence system.