The Burkholderia cenocepacia LysR-Type Transcriptional Regulator ShvR Influences Expression of Quorum-Sensing, Protease, Type II Secretion, and afc Genes

Abstract

Burkholderia cenocepacia is a significant opportunistic pathogen in individuals with cystic fibrosis. ShvR, a LysR-type transcriptional regulator, has previously been shown to influence colony morphology, biofilm formation, virulence in plant and animal infection models, and some quorum-sensing-dependent phenotypes. In the present study, it was shown that ShvR negatively regulates its own expression, as is typical for LysR-type regulators. The production of quorum-sensing signal molecules was detected earlier in growth in the shvR mutant than in the wild type, and ShvR repressed expression of the quorum-sensing regulatory genes cepIR and cciIR. Microarray analysis and transcriptional fusions revealed that ShvR regulated over 1,000 genes, including the zinc metalloproteases zmpA and zmpB. The shvR mutant displayed increased gene expression of the type II secretion system and significantly increased protease and lipase activities. Both ShvR and CepR influence expression of a 24-kb genomic region adjacent to shvR that includes the afcA and afcC operons, required for the production of an antifungal agent; however, the reduction in expression was substantially greater in the shvR mutant than in the cepR mutant. Only the shvR mutation resulted in reduced antifungal activity against Rhizoctonia solani. ShvR, but not CepR, was shown to directly regulate expression of the afcA and afcC promoters. In summary, ShvR was determined to have a significant influence on the expression of quorum-sensing, protease, lipase, type II secretion, and afc genes.

The Type II Secretion Pathway in Vibrio cholerae Is Characterized by Growth Phase-Dependent Expression of Exoprotein Genes and Is Positively Regulated by σ E

“…Together, these results suggest that quorum sensing may influence the transcription of T2S genes in V. cholerae. A positive effect of quorum sensing on expression of the genes encoding the T2S pathway was also observed in Erwinia carotovora, Pseudomonas aeruginosa, and Burkholderia cenocepacia (27,28).…”

“…HapR stimulates expression of T2S. Quorum sensing has been shown to positively regulate the expression of T2S in several Gram-negative bacteria (27,28). Among the V. cholerae strains utilized in our studies, only C6706 possesses a functional master regulator of quorum sensing, HapR (29,30).…”

Effect of Periodontal Pathogens on the Metatranscriptome of a Healthy Multispecies Biofilm Model

“…Similarly, homologues of the most highly expressed gene in V. parvula, a LysR substrate binding domain protein, has been associated in biofilm formation in other bacteria. Mutants of this gene in Burkholderia cenocepacia exhibit absence of extracellular matrix and reduced biofilm formation (56). L. casei showed a high number of hypothetical proteins as being overexpressed.…”

Hopanoid Production Is Required for Low-pH Tolerance, Antimicrobial Resistance, and Motility in Burkholderia cenocepacia

“…For example, every hopanoid-defective mutant, including the ⌬shc mutant, secreted proteases at levels similar to those of the wild type. In Burkholderia species, the secretion of these proteases depends on the cell envelope-spanning T2SS (46). The absence of hopanoids may not affect the function of this structure, because T2SS proteins are secreted in two steps, first being transported across the inner membrane into the periplasm and then being translocated across the outer membrane (26).…”