• Title/Summary/Keyword: QUORUM

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Regulation of Class II Bacteriocin Production by Cell-Cell Signaling

  • Quadri, Luis E.N.
    • Journal of Microbiology
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    • v.41 no.3
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    • pp.175-182
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    • 2003
  • Production of ribosomally synthesized antimicrobial peptides usually referred to as bacteriocins is an inducible trait in several gram positive bacteria, particularly in those belonging to the group of lactic acid bacteria. In many of these organisms, production of bacteriocins is inducible and induction requires secretion and extracellular accumulation of peptides that act as chemical messengers and trigger bacteriocin production. These inducer peptides are often referred to as autoinducers and are believed to permit a quorum sensing-based regulation of bacteriocin production. Notably, the peptides acting as autoinducers are dedicated peptides with or without antimicrobial activity or the bacteriocins themselves. The autoinducer-dependent induction of bacteriocin production requires histidine protein kinases and response regulator proteins of two-component signal transduction systems. The current working model for the regulation of class II bacteriocin production in lactic acid bacteria and the most relevant direct and indirect pieces of evidence supporting the model are discussed in this minireview.

Quorum Sensing of Rhodobacter sphaeroides Negatively Regulates Cellular Poly-$\beta$-Hydroxybutyrate Content Under Aerobic Growth Conditions

  • Lee, Jeong-K.;Kho, Dhong-Hyo;Jang, Ji-Hee;Kim, Hye-Sun;Kim, Kun-Soo
    • Journal of Microbiology and Biotechnology
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    • v.13 no.3
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    • pp.477-481
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    • 2003
  • The community escape response of Rhodobacter sphaeroides is exerted through the action of CerR and CerI, which code for a LuxR-type regulatory protein and acylhomoserine lactone synthase, respectively. Deletion of chromosomal DNA including cerR and cerI (mutant RI) or insertional interruption of cert (mutant AP3) resulted in two-fold increase in the cellular poly-${\beta}$-hydroxybutyrate (PHB) content In comparison with the wild-type under aerobic growth conditions. The PHB synthase (PhbC) activities of the cer mutants were doubled, and the enzyme expression was regulated at the level of phbC transcription. Thus, CerR, possibly in response to autoinducer (AI), appears to modulate the PHB content of aerobically grown cells by downregulating phbC transcription.

Burkholderia Diversity and Versatility: An Inventory of the Extracellular Products

  • Vial, Ludovic;Groleau, Marie-Christine;Dekimpe, Valerie;Deziel, Eric
    • Journal of Microbiology and Biotechnology
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    • v.17 no.9
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    • pp.1407-1429
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    • 2007
  • The Burkholderia genus consists of over 40 Gram-negative, ${\beta}$-proteobacteria species that occupy remarkably diverse ecological niches. This genus contains species pathogenic to human, animals, and plants, as well as species involved in promoting plant growth and biodegradation of pollutants. This is largely explained by the extraordinary versatility of Burkholderia, as reflected by the remarkable diversity of extracellular products released by these bacteria. We exhaustively surveyed the extracellular enzymes, siderophores, toxins, antimicrobials, and other secondary metabolites produced by the members of this very diverse genus. Available information on regulation, especially quorum sensing mechanisms, and secretion is highlighted.

Inhibitory Effect of Pentose on Biofilm Formation by Oral Bacteria

  • Lee, Young-Jong;Baek, Dong-Heon
    • 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.

Classification of Bacillus Beneficial Substances Related to Plants, Humans and Animals

  • Mongkolthanaruk, Wiyada
    • Journal of Microbiology and Biotechnology
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    • v.22 no.12
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    • pp.1597-1604
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    • 2012
  • Genus Bacillus is a spore-forming bacterium that has unique properties in cell differentiation, allowing the forming of spores in stress conditions and activated in the vegetative cell, with suitable environments occurring during the life cycle acting as a trigger. Their habitat is mainly in soil; thus, many species of Bacillus are associated with plants as well as rhizosphere bacteria and endophytic bacteria. Signal transduction is the principal mechanism of interactions, both within the cell community and with the external environment, which provides the subsequent functions or properties for the cell. The antimicrobial compounds of Bacillus sp. are potentially useful products, which have been used in agriculture for the inhibition of phytopathogens, for the stimulation of plant growth, and in the food industry as probiotics. There are two systems for the synthesis of these substances: nonribosomal synthesis of cyclic lipopeptides (NRPS) and polyketides (PKS). For each group, the structures, properties, and genes of the main products are described. The different compounds described and the way in which they co-exist exhibit the relationship of Bacillus substances to plants, humans, and animals.