Natural Competence Essay

Natural competence is regulated by competence stimulating peptides, CSPs. Natural competence is the ability for cells to take up naked DNA, or DNA that is not a part of a living cell anymore. Naked, extracellular DNA can be found in the matrix due to two reasons, cells secreting it or cell death/lysis. CSPs act as quorum sensing molecules and tell the cells when there is a large population of cells in the surrounding area. Thus CSPs have the ability to control the expression of certain proteins. CSPs work by an induction through the ComCDE pathway once a certain density is reached in the biofilm. The cascade begins with the interaction of the CSP with its histadine kinase receptor, ComD. The kinase receptor responds by transferring a phosphate group to ComE, the cognate response regulator. ComE phosphorylase the correct protein. After phosphorylation, the response regulator activates transcription of several genes containing a ComE binding site, ComX. Expression of ComX
CipI is the bacteriocin immunity protein that prevents cell lysis while CipB is the bacteriocin that causes cell lysis when it is expressed. It can be seen that at high concentrations of CSPs, there is more expression of CipI and CipB. In order to determine why CipI and CipB are important, strains of Streptococcus were tested. The amount of exogenous DNA, eDNA, in the matrix was measured in strains without either CipI or CipB after being exposed to CSPS. When there were high concentrations of CSPs, the strains without the CipI, the immunity, had a lot of eDNA in the matrix. In high concentrations of CSPs, the strains without the CipB showed low amounts of eDNA than the previous situation and the control. When the CipB, the bacteriocin, was not present, it can be seen that there was less cell lysis. This means that CipI and CipB help to control the amount of DNA in the matrix by causing cell lysis in the presence of