Contribution of the Sensor Histidine Kinases PhcS and VsrA to the Quorum Sensing of Strain OE1-1.

The soilborne Gram-negative phytopathogenic beta-proteobacterium strain OE1-1 produces methyl 3-hydroxymyristate (3-OH MAME) as the quorum sensing (QS) signal by the methyltransferase PhcB and senses the chemical, activating the LysR family transcriptional regulator PhcA, which regulates the QS-dependent genes responsible for QS-dependent phenotypes including virulence. The sensor histidine kinases PhcS and VsrA are reportedly involved in the regulation of QS-dependent genes. To elucidate the function of PhcS and VsrA in the active QS, we generated the deletion and -deletion mutants, which exhibited weak changes to their QS-dependent phenotypes including virulence.

The Micacocidin Production-Related Deletion Alters the Quorum Sensing-Dependent Gene Regulation of Strain OE1-1.

The soil-borne phytopathogenic gram-negative bacterium species complex (RSSC) produces staphyloferrin B and micacocidin as siderophores that scavenge for trivalent iron (Fe) in the environment, depending on the intracellular divalent iron (Fe) concentration. The staphyloferrin B-deficient mutant reportedly retains its virulence, but the relationship between micacocidin and virulence remains unconfirmed. To elucidate the effect of micacocidin on RSSC virulence, we generated the micacocidin productivity-deficient mutant (Δ) that lacks , which encodes a putative polyketide synthase/non-ribosomal peptide synthetase, using the RSSC phylotype I strain OE1-1.

The transcription regulator ChpA affects the global transcriptome including quorum sensing-dependent genes in Ralstonia pseudosolanacearum strain OE1-1.

The gram-negative plant-pathogenic β-proteobacterium Ralstonia pseudosolanacearum strain OE1-1 produces methyl 3-hydroxymyristate as a quorum sensing (QS) signal through methyltransferase PhcB and senses the chemical via the sensor histidine kinase PhcS. This leads to activation of the LysR family transcription regulator PhcA, which regulates the genes (QS-dependent genes) responsible for QS-dependent phenotypes, including virulence. The transcription regulator ChpA, which possesses a response regulator receiver domain and also a hybrid sensor histidine kinase/response regulator phosphore-acceptor domain but lacks a DNA-binding domain, is reportedly involved in QS-dependent biofilm formation and virulence of R.

β-1,4-Cellobiohydrolase is involved in full expression of phcA, contributing to the feedback loop in quorum sensing of Ralstonia pseudosolanacearum strain OE1-1.

After infecting roots of tomato plants, the gram-negative bacterium Ralstonia pseudosolanacearum strain OE1-1 activates quorum sensing (QS) to induce production of plant cell wall-degrading enzymes, such as β-1,4-endoglucanase (Egl) and β-1,4-cellobiohydrolase (CbhA), via the LysR family transcriptional regulator PhcA and then invades xylem vessels to exhibit virulence. The phcA-deletion mutant (ΔphcA) exhibits neither the ability to infect xylem vessels nor virulence. Compared with strain OE1-1, the egl-deletion mutant (Δegl) exhibits lower cellulose degradation activity, lower infectivity in xylem vessels, and reduced virulence.