Dual-function quorum-sensing systems in bacterial pathogens and symbionts
Fig 2
Vibrio signaling pathways for QS and host sensing.
Various HK receptors in Vibrio species recognize distinct signals produced by the bacterium (sensing “self”) and/or produced by host cells or neighboring bacteria (sensing “other”). The conservation of the HKs varies among species, and this figure indicates the proteins and signals determined in the literature for each species (V.h, Vibrio harveyi; V.c., Vibrio cholerae; V.p., Vibrio parahaemolyticus; V.f., Vibrio fischeri). Signals produced by enzymes (if known) are indicated for each system. In the absence of cognate signals, phosphorylation (P) of LuxU and LuxO leads to production of AphA and low production of LuxR (V.h.)/HapR (V.c.)/OpaR (V.p.)/LitR (V.f.) and expression of biofilm, virulence, and type III secretion genes. In the presence of signals, dephosphorylation of LuxU drives production of LuxR/HapR/OpaR/LitR and expression of bioluminescence, proteases, and type VI secretion genes. The NO/H-NOX/HahK pathway in V.f. inhibits syp gene expression and biofilm formation. The VqmA/DPO pathway inhibits biofilm formation in V.c. AI-2, autoinducer-2; CAI-1, cholera autoinducer-1; CP, cytoplasm; DPO, 3,5-dimethyl-pyrazin-2-ol; HAI-1, harveyi autoinducer-1; HK, histidine kinase; H-NOX, heme nitric oxide/oxygen binding; NO, nitric oxide; PP, periplasm; QS, quorum sensing. Created with BioRender.com.