How does Quorum Sensing of Intestinal Bacteria Affect Our Health and Mental Status?

The human gut is host to almost 3000 microbial species, of which 90% are bacteria. Quorum sensing (QS) molecules generated by intestinal bacteria are important in establishing species- and strain-level structures within the gut microbiome but are also used to communicate with the host. Although we do not know which QS molecules have the most direct interaction with intestinal and sensory neurons, it is clear they affect our physiological and mental health. Signals produced by bacteria are diverse and include autoinducers (AIs), homoserine lactones (HSLs), quinolines, peptides, toxins and proteases. These signaling molecules activate specific receptors in the bacterial cell wall and trigger sensors in the cytoplasm that regulate gene expressions. A better understanding of the gene structures encoding the production of QS molecules is of importance when selecting strains with neurogenerative and other probiotic properties. Furthermore, QS molecules may be used as biomarkers in the diagnosis of inflammable bowel disease (IBD), irritable bowel syndrome (IBS) and colorectal cancer (CRC). In the future, it should be possible to use QS biomarkers to diagnose neurological and psychiatric diseases such as anxiety and depression, major depressive disorder (MDD), schizophrenia, bipolar disorder, autism and obsessive-compulsive disorder (OCD).