The steps need to be arranged as follows:
1. S.aureus grow at low density on skin surface.
2. S.aureus enter tissue through a wound.
3. S.aureus grow to high density inside the tissue.
4. S.aureus sense quorum through only the Agr pathway.
5. S.aureus secrete toxin.
S.aureus is a bacterium which can be found in the normal flora of the body, however, under specific conditions, it can become pathogenic and cause skin and respiratory infections and food poisoning. Quorum sensing is a method used by bacteria for cell-to-cell communication and coordination of their colonization. Bacteria secrete signalling molecules to communicate and as the population grows so does the concentration of the signalling molecules. When the signalling molecules reach a specific concentration, then the expression of a specific gene is triggered. This gene is agr and it regulates the secretion of toxins which constitute the pathogenic mechanism of the bacterium.
