Genetic Networks and Gene Regulation Mechanisms for Quorum Sensing and Quorum Quenching in Bacteria

Dear Colleagues,

Many bacterial activities, including the synthesis of secondary metabolites, enzymes and virulence factors, are modulated by quorum sensing (QS), a sophisticated cell-to-cell communication mechanism based on small diffusible molecules that alter the expression of a whole network of genes (up to 25% of the genome in some cases) when population density reaches a critical threshold. The number of chemically different molecules described as QS signals has constantly increased in the past two decades. Molecular mimics and antagonists produced by eukaryotic organisms and examples of quorum quenching activities that interfere with bacterial QS have also been identified, and may be more widespread than initially expected.

There is still much to be learned about the regulatory mechanisms in which these molecules participate and how QS enables bacteria to coordinate activities, an issue that has significant interest from the perspective of social evolution, fitness and the benefits at the population level associated with costly co-operative behaviours. Inhibiting gene expression when population density is low could serve this purpose, for example, by delaying virulence factor production until enough cells amass to produce effective levels. Restrained gene expression may also benefit groups by enabling coordinated “sneak attacks” during infection, and hiding factors that could be recognized as antigens by the immune system until a large force assembles.

In complex environments, the size of the quorum is not fixed but varies according to the relative rates of production and loss of signal molecules, which depend on many naturally fluctuating environmental parameters. Thus, quorum sensing can also be considered in the context of ‘diffusion sensing’ (DS), ‘compartment sensing’ (CS) or ‘efficiency sensing’ (ES), where the signal molecule supplies information with respect to the local environment and spatial distribution of the cells rather than, or as well as, cell population density.

This Special Issue will explore recent advances and future research avenues on quorum sensing and quorum quenching genomics and genetic networks, and molecular mechanisms of gene expression regulation mediated by signalling molecules.

Dr. Manuel Espinosa Urgel
Dr. Inmaculada Llamas
Guest Editors

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