Cell-cell communication in bacteria occurs through small diffusible chemical signals that affect target gene expression in response to cell density. This form of intercellular bacterial signaling is known as quorum sensing and synchronizes metabolic and behavioral activities of a community of bacteria. Many of the activities which are regulated involve virulence associated factors in bacterial pathogens and symbiotic traits in host-beneficial bacteria. This is therefore a mechanism which controls multicellular behavior in bacteria and deeper understanding promises to shed light on the complexities of the host-microbe relationship and may lead to novel therapeutic applications. Bacterial quorum sensing has also introduced the aspect of bacteria being social organisms since via quorum sensing regulate the production of secreted ‘public goods’ which are available to all the neighboring bacterial population. During the seminar, quorum sensing will be introduced and current research lines in ICGEB-Bacteriology will be highlighted.