Dataset Information

Impact of QseBC system in c-di-GMP-dependent quorum sensing regulatory network in a clinical isolate SSU of Aeromonas hydrophila.

ABSTRACT: Our earlier studies showed that AhyRI- (AI-1) and LuxS-based (AI-2) quorum sensing (QS) systems were positive and negative regulators of virulence, respectively, in a diarrheal isolate SSU of Aeromonas hydrophila. Recently, we demonstrated that deletion of the QseBC two-component signal transduction system (AI-3 QS in enterohemorrhagic Escherichia coli) also led to an attenuation of A. hydrophila in a septicemic mouse model of infection, and that interplay exists between AI-1, AI-2, and the second-messenger cyclic-di-guanosine monophosphate (c-di-GMP) in modulating bacterial virulence. To further explore a network connection between all of the three QS systems in A. hydrophila SSU and their cross talk with c-di-GMP, we overproduced a protein with a GGDEF domain, which increases c-di-GMP levels in bacteria, and studied phenotypes and transcriptional profiling of genes involved in biofilm formation and motility of the wild-type (WT) A. hydrophila and its ?qseB mutant. Over-expression of the GGDEF domain-encoding gene (aha0701h) resulted in a significantly reduced motility of the WT A. hydrophila similar to that of the ?qseB mutant. While enhanced protease production was noted in WT A. hydrophila that had increased c-di-GMP, no enzymatic activity was detected in the ?qseB mutant overexpressing the aha0701h gene. Likewise, denser biofilm formation was noted for WT bacteria when c-di-GMP was overproduced compared to its respective control; however, overproduction of c-di-GMP in the ?qseB mutant led to reduced biofilm formation, a finding similar to that noted for the parental A. hydrophila strain. These effects on bacterial motility and biofilm formation in the ?qseB mutant or the mutant with increased c-di-GMP were correlated with altered levels of fleN and vpsT genes. While we noted transcript levels of qseB and qseC genes to be increased in the ahyRI mutant, down-regulation of the ahyR and ahyI genes was observed in the ?qseB mutant, which correlated with decreased protease activity. Finally, an enhanced virulence of WT A. hydrophila with increased c-di-GMP was noted in a mouse model when compared to findings in the parental strain with vector alone. Overall, we conclude that cross talk between AI-1 and QseBC systems exists in A. hydrophila SSU, and c-di-GMP modulation on QseBC system is dependent on the expression of the AI-1 system.

SUBMITTER: Kozlova EV

PROVIDER: S-EPMC3422430 | biostudies-literature | 2012 Sep

REPOSITORIES: biostudies-literature

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Impact of QseBC system in c-di-GMP-dependent quorum sensing regulatory network in a clinical isolate SSU of Aeromonas hydrophila.

Kozlova Elena V EV Khajanchi Bijay K BK Popov Vsevolod L VL Wen Julie J Chopra Ashok K AK

Microbial pathogenesis 20120601 3-4

Our earlier studies showed that AhyRI- (AI-1) and LuxS-based (AI-2) quorum sensing (QS) systems were positive and negative regulators of virulence, respectively, in a diarrheal isolate SSU of Aeromonas hydrophila. Recently, we demonstrated that deletion of the QseBC two-component signal transduction system (AI-3 QS in enterohemorrhagic Escherichia coli) also led to an attenuation of A. hydrophila in a septicemic mouse model of infection, and that interplay exists between AI-1, AI-2, and the seco ...[more]

PMID: 22664750

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Project description:Bacterial motility is critical for symbiotic colonization by Vibrio fischeri of its host, the squid Euprymna scolopes, facilitating movement from surface biofilms to spaces deep inside the symbiotic organ. While colonization has been studied traditionally using strain ES114, others, including KB2B1, can outcompete ES114 for colonization for a variety of reasons, including superior biofilm formation. We report here that KB2B1 also exhibits an unusual pattern of migration through a soft agar medium: whereas ES114 migrates rapidly and steadily, KB2B1 migrates slowly and then ceases migration. To better understand this phenomenon, we isolated and sequenced five motile KB2B1 suppressor mutants. One harbored a mutation in the gene for the cAMP receptor protein (crp); because this strain also exhibited a growth defect, it was not characterized further. Two other suppressors contained mutations in the quorum sensing pathway that controls bacterial bioluminescence in response to cell density, and two had mutations in the diguanylate cyclase (DGC) gene VF_1200. Subsequent analysis indicated that (1) the quorum sensing mutations shifted KB2B1 to a perceived low cell density state and (2) the high cell density state inhibited migration via the downstream regulator LitR. Similar to the initial point mutations, deletion of the VF_1200 DGC gene increased migration. Consistent with the possibility that production of the second messenger c-di-GMP inhibited the motility of KB2B1, reporter-based measurements of c-di-GMP revealed that KB2B1 produced higher levels of c-di-GMP than ES114, and overproduction of a c-di-GMP phosphodiesterase promoted migration of KB2B1. Finally, we assessed the role of viscosity in controlling the quorum sensing pathway using polyvinylpyrrolidone and found that viscosity increased light production of KB2B1 but not ES114. Together, our data indicate that while the two strains share regulators in common, they differ in the specifics of the regulatory control over downstream phenotypes such as motility.

Dataset Information

Impact of QseBC system in c-di-GMP-dependent quorum sensing regulatory network in a clinical isolate SSU of Aeromonas hydrophila.

Publications

Impact of QseBC system in c-di-GMP-dependent quorum sensing regulatory network in a clinical isolate SSU of Aeromonas hydrophila.

Similar Datasets

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