Quorum sensing and host cell reprogramming.

Quorum sensing (QS) is a mechanism that allows bacteria to coordinate their behavior based on population density through the production and detection of small signaling molecules. This process regulates several important functions, including virulence, biofilm formation, and metabolic adaptation. In recent years, it has become clear that QS signals are not limited to communication among bacteria but can also influence host cells during infection. At the same time, host cells respond to microbial invasion by undergoing coordinated changes in gene expression, chromatin structure, and metabolism, a process commonly referred to as host cell reprogramming. Studies now show that QS molecules such as acyl-homoserine lactones, autoinducing peptides, and quinolone signals can interact with host signaling pathways, including NF-κB, MAPK, and PI3K/Akt. These interactions affect immune responses, epithelial barrier function, and cellular metabolism, often favouring pathogen survival. This chapter summarizes current understanding of quorum sensing mechanisms, highlights their roles in major pathogens, and discusses how these signals influence host cellular processes. These insights may help guide the development of new anti-virulence strategies.