Quorum-sensing

Light is emitted by bacteria living in the light organs of fish 1970s Vibrio fischeri e V. harveyi Symbionts, inhabitants of the light organs of fish and squids. Bacterial densities: 1010 – 1011 CFU/mL.

Light is produced after transcription activation of the lux operon

Synthesis of HSL – a signaling molecule

Signaling molecules are diverse

Swarming of different Pseudomonas aeruginosa strains after 48 h on FAB-glucose medium with 0.45% noble agar. Morris J D et al. Appl. Environ. Microbiol. 2011;77:8310-8317

The Tojan horse

Qurum sensing regulation

Pseudomonas aeruginosa LasI/LasR, rhlI/rhlR and PQS quorum-sensing systems

S. aureus Agr QS circuit. The autoinducing peptide (AIP) is synthesized as a precursor from agrD. The AIP transporter AgrB processes the precursor to the mature AIP and transports it out of the cell. AIPs are detected by a two-component signal transduction pathway. AgrC is the membrane-bound histidine kinase and AgrA is the response regulator. Phosphorylated AgrA activates the P2 and P3 promoters encoding the agr operon (called RNAII) and the RNAIII regulatory RNA, respectively. RNAIII posttranscriptionally activates virulence factor production and represses expression of rot, the repressor of toxins, leading to further derepression of virulence factors. Rutherford S T , and Bassler B L Cold Spring Harb Perspect Med 2012;2:a012427

Bacterial Biofilms Structured communities of bacteria living together

Formation of biofilms

https://www.youtube.com/watch?v=YJWKWYQfSi0

Quorum-quenching

P. aeruginosa AIs and inhibitors. Rutherford S T , and Bassler B L Cold Spring Harb Perspect Med 2012;2:a012427

Lactonases – enzymes that destroy the lactonde ring of AHLs