Autoinducing peptides (AIP) from Gram-positive bacteria allow intercellular communication, termed quorum sensing. AIPs often have dedicated exporters; their release from the bacteria and the extracellular concentration is then sensed by a receptor linked to a two-component system. Multiple receptors may recognise an AIP, while AIPs from different species are known to inhibit each other’s receptor binding.
AIPs allow a coordinated response to cell density and growth phase to modulate the expression of various compounds, particularly virulence factors, genetic competence, and antimicrobial peptides. In some instances, such as nisin from Lactococcus lactis, the AIP can have dual functionality for quorum sensing and an antimicrobial peptide.
The importance of AIPs in quorum sensing is evident by the vast array of organisms found with them and the presence of multiple quorum sensing systems to allow intercellular communication. Due to their prevalence and critical role in cell growth and virulence, extensive research is underway to try and understand how AIP may be utilised to inhibit infections by Gram-negative human pathogens.