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

Abstract

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).

Diffusible signal factors (DSFs) bind and repress VirF, the leading virulence activator of Shigella flexneri

“…the processes depending on resident microorganisms acting against enteric pathogens based on competition for nutrients, metabolic exclusion, O 2 consumption, bacteriocin or antimicrobial peptide production, and QS interference 38 – 40 . Bacterial pathogens use their autoinducers to coordinate the expression of virulence factors and influence the host response 41 . In addition, bacterial pathogens can eavesdrop on host- and commensal-derived signalling molecules to spatially orient themselves and optimise virulence expression at the site of infection 38 , 42 .…”

Conversations in the Gut: The Role of Quorum Sensing in Normobiosis

“…Several factors, like dietary changes and the use of antibiotics, have been shown to cause dysbiosis, an imbalance in gut microbiota. This dysbiosis is associated with a number of disorders such as inflammatory bowel disease, cancer, obesity, depression, and autism [ 18 , 19 , 20 , 21 ].…”

“…IL-8, induced by the pro-inflammatory cytokine IL-1 [ 187 ], was recently demonstrated to be downregulated, together with tumor necrosis factor (TNF), by 3-oxo-C12:2-HSL via bitter taste receptors [ 188 ]. While AI-3 could induce inflammatory reactions in a similar manner to other pyrazinones [ 79 ] through the expression of IL-8 [ 20 , 96 ], 3-oxo-C12:2-HSL [ 93 ] and AI-2 [ 189 ] were reported to reduce inflammation.…”

Biofilm Formation of Clostridioides difficile, Toxin Production and Alternatives to Conventional Antibiotics in the Treatment of CDI

“…Two communication or quorum sensing (QS) systems have been identified in C. difficile , i.e., an inter-species LuxSCD system (top section of Figure 2 ) and an intra-species accessory gene regulator (Agr) system (bottom section of Figure 2 ). Genes encoding homologues of luxS have also been detected in C. difficile [ 68 , 69 , 70 , 71 , 72 , 73 ]. The luxS gene encodes AI-2 synthase (LuxS).…”