S. pneumoniae is human pathogenic bacterium in which the process of genetic transformation was first described in the 1930s.  In order for a bacterium to take up exogenous DNA from its surroundings, it must become competent.  In S. pneumoniae, a number of complex events must occur to achieve a competent state, but it is believed that quorum sensing plays a role.   Competence stimulating peptide (CSP) is a 17-amino acid peptide autoinducer required for competency and subsequent genetic transformation.  CSP is produced by proteolytic cleavage of a 41-amino acid precursor peptide (ComC); is secreted by an ABC transporter (ComAB); and is detected by a sensor kinase protein (ComD) once it has reached a threshold concentration.  Detection is followed by autophosphorylation of ComD, which in turn, phosphorylates ComE.  ComE is a response regulator responsible for activating transcription of comX, the product of which is required to activate transcription of a number of other genes involved in the development of competence.