• International Journal of Oral Biology
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• v.35 no.4
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• pp.203-207
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• 2010

A number of bacterial species coexist in oral cavities as a biofilm rather than a planktonic arrangement. By forming an oral biofilm with quorum sensing properties, microorganisms can develop a higher pathogenic potential and stronger resistance to the host immune system and antibiotics. Hence, the inhibition of biofilm formation has become a major research issue for the future prevention and treatment of oral diseases. In this study, we investigated the effects of pentose on biofilm formation and phenotypic changes using wild type oral bacteria obtained from healthy human saliva. D-ribose and D-arabinose were found to inhibit biofilm formation, but have no effects on the growth of each oral bacterium tested. Pentoses may thus be good candidate biofilm inhibitors without growth-inhibition activity and be employed for the future prevention or treatment of oral diseases.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.25-26
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• 2005

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2003.06a
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• pp.159-160
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• 2003

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.161-161
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• 2008

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.35-36
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• 2008

• Journal of Microbiology and Biotechnology
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• v.24 no.12
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• pp.1609-1621
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• 2014

The plant pathogen Burkholderia gladioli, which has a broad host range that includes rice and onion, causes bacterial panicle blight and sheath rot. Based on the complete genome sequence of B. gladioli BSR3 isolated from infected rice sheaths, the genome of B. gladioli BSR3 contains the luxI/luxR family of genes. Members of this family encode N-acyl-homoserine lactone (AHL) quorum sensing (QS) signal synthase and the LuxR-family AHL signal receptor, which are similar to B. glumae BGR1. In B. glumae, QS has been shown to play pivotal roles in many bacterial behaviors. In this study, we compared the QS-dependent gene expression between B. gladioli BSR3 and a QS-defective B. gladioli BSR3 mutant in two different culture states (10 and 24 h after incubation, corresponding to an exponential phase and a stationary phase) using RNA sequencing (RNA-seq). RNA-seq analyses including gene ontology and pathway enrichment revealed that the B. gladioli BSR3 QS system regulates genes related to motility, toxin production, and oxalogenesis, which were previously reported in B. glumae. Moreover, the uncharacterized polyketide biosynthesis is activated by QS, which was not detected in B. glumae. Thus, we observed not only common QS-dependent genes between B. glumae BGR1 and B. gladioli BSR3, but also unique QS-dependent genes in B. gladioli BSR3.

• The Plant Pathology Journal
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• v.29 no.2
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• pp.182-192
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• 2013

Numerous root-associated bacteria (rhizobacteria) are known to elicit induced systemic resistance (ISR) in plants. Bacterial cell-density-dependent quorum sensing (QS) is thought to be important for ISR. Here, we investigated the role of QS in the ISR elicited by the rhizobacterium, Serratia marcescens strain 90-166, in tobacco. Since S. marcescens 90-166 produces at least three QS signals, QS-mediated ISR in strain 90-166 has been difficult to understand. Therefore, we investigated the ISR capacity of two transgenic tobacco (Nicotiana tabacum) plants that contained either bacterial acylhomoserine lactone-producing (AHL) or -degrading (AiiA) genes in conjunction with S. marcescens 90-166 to induce resistance against bacterial and viral pathogens. Root application of S. marcescens 90-166 increased ISR to the bacterial pathogens, Pectobacterium carotovorum subsp. carotovorum and Pseudomonas syringae pv. tabaci, in AHL plants and decreased ISR in AiiA plants. In contrast, ISR to Cucumber mosaic virus was reduced in AHL plants treated with S. marcescens 90-166 but enhanced in AiiA plants. Taken together, these data indicate that QS-dependent ISR is elicited by S. marcescens 90-166 in a pathogen-dependent manner. This study provides insight into QS-dependent ISR in tobacco elicited by S. marcescens 90-166.

• The Plant Pathology Journal
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• v.29 no.3
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• pp.249-259
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• 2013

Burkholderia glumae causes rice grain rot and sheath rot by producing toxoflavin, the expression of which is regulated by quorum sensing (QS). The QS systems of B. glumae rely on N-octanoyl homoserine lactone, synthesized by TofI and its cognate receptor TofR, to activate the genes for toxoflavin biosynthesis and an IclR-type transcriptional regulator gene, qsmR. To understand genome-wide transcriptional profiling of QS signaling, we employed RNAseq of the wild-type B. glumae BGR1 with QS-defective mutant, BGS2 (BGR1 tofI::${\Omega}$) and QS-dependent transcriptional regulator mutant, BGS9 (BGR1 qsmR::${\Omega}$). A comparison of gene expression profiling among the wild-type BGR1 and the two mutants before and after QS onset as well as gene ontology (GO) enrichment analysis from differential expressed genes (DEGs) revealed that genes involved in motility were highly enriched in TofI-dependent DEGs, whereas genes for transport and DNA polymerase were highly enriched in QsmR-dependent DEGs. Further, a combination of pathways with these DEGs and phenotype analysis of mutants pointed to a couple of metabolic processes, which are dependent on QS in B. glumae, that were directly or indirectly related with bacterial motility. The consistency of observed bacterial phenotypes with GOs or metabolic pathways in QS-regulated genes implied that integration RNAseq with GO enrichment or pathways would be useful to study bacterial physiology and phenotypes.

• Food Science of Animal Resources
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• v.40 no.6
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• pp.1001-1013
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• 2020

The formation of biofilms on the enamel surface of teeth by Streptococcus mutans is an important step in dental plaque formation, demineralization, and early caries because the biofilm is where other bacteria involved in dental caries attach, grow, and proliferate. The objectives of this study were to determine the effect of phosvitin (PSV) on the biofilm formation, exopolysaccharides (EPS) production, adherence activity of S. mutans, and the expression of genes related to the compounds essential for biofilm formation (quorum-sensing inducers and components of biofilm matrix) by S. mutans. PSV significantly reduced the biofilm-forming activity of S. mutans and increased the degradation of preformed biofilms by S. mutans. PSV inhibited the adherence activity of S. mutans by 31.9%-33.6%, and the production of EPS by 62%-65% depending upon the strains and the amount of PSV added. The expressions of genes regulating the production of EPS and the quorum-sensing-inducers (gtfA, gtfD, ftf, relA, vicR, brpA, and comDE) in all S. mutans strains were down-regulated by PSV, but gtfB was down-regulated only in S. mutans KCTC 5316. Therefore, the anti-biofilm-forming activity of PSV was accomplished through the inhibition of biofilm formation, adherence activity, and the production of quorum-sensing inducers and EPS by S. mutans.

• Journal of Microbiology and Biotechnology
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• v.18 no.5
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• pp.828-836
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• 2008

The biocontrol rhizobacterium Pseudomonas sp. M18 can produce two kinds of antibiotics, namely pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA), and is antagonistic against a number of soilborne phytopathogens. In this study, a luxR-type quorum-sensing regulatory gene, vqsR, was identified and characterized immediately downstream of the Plt gene cluster in strain MI8. A vqsR-inactivated mutant led to a significant decrease in the production of Plt and its biosynthetic gene expression. However, this was restored when introducing the vqsR gene by cloning into the plasmid pME6032 in trans. The vqsR mutation did not exert any obvious influence on the production of PCA and its biosynthetic gene expression and the production of N-acylhomoserine lactones (C4 and C8-HSLs) and their biosynthetic gene rhlI expression. Accordingly, these results introduce VqsR as a regulator of Plt production in Pseudomonas spp., and suggest that the regulatory mechanism of vqsR in strain M18 is distinct from that in P. aeruginosa. In addition, it was demonstrated that vqsR mutation did not have any obvious impact on the expression of Plt-specific ABC transporters and other secondary metabolic global regulators, including GacA, RpoS, and RsmA.