it would be a little value for just a few bacterial cells to produce a gene product such as an enzyme or virulence protein because the concentration of the protein would be too low to be effective
quorum sensing is a type of regulatory process that ensures there is a sufficient cell density before a specific gene product is made
this process allows bacteria to increase in numbers before starting to produce a particular gene product such as an extracellular enzyme or a virulence protein
each species that employs quorum sensing produces a small signal moluecule.in gram negative bacteria,the signal molecule is an acyl homoserine lactone
when the acyl homoserine lactone signal molecule reaches a threshold concentration,it binds to and activates a regulatory protein,which then to a specific site on the DNA
the binding of this regulatory protein transcription activator results in production of the specific quorum-dependent protein as well as more enzymes to make the acyl homoserine lactone
quorum sensing in gram positive bacteria involves a different type of signal molecule.a precursor oligopeptide is cleaved into functional signal molecules of 10 to 20 amino acids
these molecules are actively transported out of the cell through a special transporter protein
when the signal oligopeptides reach a threshold concentration on the outside of the cell,they are detected by a sensor protein on the surface of the cell
when the oligopeptide reacts with the sensor protein,the protein becomes phosphorylated on the inside of the cell membrane
the phophate is then transferred to a response regulator protein which allows it to bind to a specific site on the DNA.this binding results in alteration in the transcription of target genes
Quorum-dependent protein such as specific virulence factors are peodeced