Editing Quorum sensing (section)

====''Streptococcus pneumoniae''====

Each year ''Streptococcus pneumoniae'' kills more than a million people, even though vaccines are available.<ref>{{cite journal |vauthors=Junges R, Salvadori G, Shekhar S, Åmdal HA, Periselneris JN, Chen T, Brown JS, Petersen FC |title=A Quorum-Sensing System That Regulates Streptococcus pneumoniae Biofilm Formation and Surface Polysaccharide Production |journal=mSphere |volume=2 |issue=5 |pages= |date=2017 |pmid=28932816 |pmc=5597970 |doi=10.1128/mSphere.00324-17 |url=}}</ref>  A complex quorum sensing system has evolved in ''S. pneumoniae'' that regulates [[bacteriocin]] production.  This system also enables entry into the [[natural competence|competent state]] essential for natural [[genetic transformation]].<ref>{{cite journal |vauthors=Shanker E, Federle MJ |title=Quorum Sensing Regulation of Competence and Bacteriocins in Streptococcus pneumoniae and mutans |journal=Genes (Basel) |volume=8 |issue=1 |date=January 2017 |page=15 |pmid=28067778 |doi=10.3390/genes8010015 |doi-access=free |pmc=5295010 |url=}}</ref>  In naturally competent ''S. pneumoniae'' the competent state is not a constitutive property.  However competence can be induced by a peptide [[pheromone]] by means of  a quorum-sensing mechanism.<ref name = Steinmoen2002>{{cite journal |vauthors=Steinmoen H, Knutsen E, Håvarstein LS |title=Induction of natural competence in Streptococcus pneumoniae triggers lysis and DNA release from a subfraction of the cell population |journal=Proc Natl Acad Sci U S A |volume=99 |issue=11 |pages=7681–6 |date=May 2002 |pmid=12032343 |doi=10.1073/pnas.112464599 |doi-access=free |pmc=124321 |bibcode=2002PNAS...99.7681S |url=}}</ref>  When the competent state is induced, this causes release of [[DNA]] from a sub-fraction of the ''S. pneumoniae'' population, probably by cell lysis.  Then most of the ''S. pneumoniae'' cells that have been induced to competence become recipients and take up the DNA released by the donors.<ref name = Steinmoen2002/>  Thus it appears that natural transformation in ''S. pneumoniae'' is a natural adaptive process for promoting [[genetic recombination]], a process that resembles [[sexual reproduction]] in higher organisms.<ref name = Steinmoen2002/>