The integron is a new type of mobile element which has evolved by a site-specific recombinational mechanism. Integrons consist of two conserved segments of DNA separated by a variable region containing one or more genes integrated as cassettes. Oligonucleotide probes specific for the conserved segments have revealed that integrons are widespread in recently isolated clinical bacteria. Also, by using oligonucleotide probes for several antibiotic resistance genes, we have found novel combinations of resistance genes in these strains. By using PCR, we have determined the content and order of the resistance genes inserted between the conserved segments in the integrons of these clinical isolates. PCR mapping of integrons can be a useful epidemiological tool to study the evolution of multiresistance plasmids and transposons and dissemination of antibiotic resistance genes.

Power is at the core of current debates over the future of trade unionism. This article provides a framework to assess the power resources and strategic capabilities central to union capacity building. We identify four key power resources: internal solidarity; network embeddedness; narrative resources that frame understandings and union actions; and infrastructural resources (material, human, processes, policies and programmes). Resources alone are not enough; unions must also be capable of using them. We identify four strategic capabilities: intermediating between contending interests to foster collaborative action and to activate networks; framing; articulating actions over time and space; and learning. Much experimentation and research on the interactions between these resources and capabilities in particular contexts is required to advance our understanding of the renewal of union power. Ré suméLe pouvoir est au coeur des débats actuels sur l'avenir du syndicalisme. Le présent article fournit un cadre d'évaluation des ressources de pouvoir et des aptitudes stratégiques pour le renforcement des capacités d'action syndicales. Les auteurs identifient quatre ressources fondamentales de pouvoir: la solidarité interne, l'ancrage dans des réseaux, les ressources discursives qui encadrent les approches et les actions des syndicats et les ressources d'infrastructure (matériel, ressources humaines, processus, politiques et programmes). Les ressources seules ne suffisent pas. Les syndicats doivent également être capables de les utiliser. Les auteurs identifient quatre aptitudes stratégiques: la médiation entre des intérêts en jeu afin de favoriser une action commune et d'activer les réseaux, l'encadrement, l'articulation d'actions dans le temps et dans l'espace, et Downloaded from l'apprentissage. Une expérimentation et une recherche accrues sur les interactions entre ces ressources et ces capacités dans des contextes particuliers sont nécessaires pour approfondir notre compréhension du renouveau du pouvoir syndical. ZusammenfassungBei den derzeitigen Debatten über die Zukunft der Gewerkschaftsbewegung spielt die Frage der Macht eine zentrale Rolle. Dieser Beitrag liefert einen Rahmen, um die Machtressourcen und strategischen Einsatzmöglichkeiten zu bewerten, die für den Kapazitätsaufbau der Gewerkschaften von entscheidender Bedeutung sind. Wir zeigen vier wichtige Machtressourcen auf: interne Solidarität; Vernetztheit; narrative Ressourcen, die Begriffen und gewerkschaftlichem Handeln einen Rahmen verleihen; und Infrastrukturressourcen (materielle und Humanressourcen, Prozesse, Strategien und Programme). Aber Ressourcen allein reichen nicht aus. Die Gewerkschaften müssen auch in der Lage sein, sie zu nutzen. Wir zeigen vier strategische Einsatzmöglichkeiten auf: Vermittlung zwischen entgegengesetzten Interessen, um gemeinsames Handeln zu stärken und Netzwerke zu aktivieren; Framing; zeitliche und räumliche Verknüpfung von Handlungen; und Lernen. Um besser zu verstehen, wie sich eine Erneuerung der gewerkschaftlichen Ma...

SummaryThe induction of genetic competence is a strategy used by bacteria to increase their genetic repertoire under stressful environmental conditions. Recently, Streptococcus pneumoniae has been shown to co-ordinate the uptake of transforming DNA with fratricide via increased expression of the peptide pheromone responsible for competence induction. Here, we document that environmental stress-induced expression of the peptide pheromone competencestimulating peptide (CSP) in the oral pathogen Streptococcus mutans. We showed that CSP is involved in the stress response and determined the CSP-induced regulon in S. mutans by microarray analysis. Contrary to pneumococcus, S. mutans responds to increased concentrations of CSP by cell lysis in only a fraction of the population. We have focused on the mechanism of cell lysis and have identified a novel bacteriocin as the 'death effector'. Most importantly, we showed that this bacteriocin causes cell death via a novel mechanism of action: intracellular action against self. We have also identified the cognate bacteriocin immunity protein, which resides in a separate unlinked genetic locus to allow its differential regulation. The role of the lytic response in S. mutans competence is also discussed. Together, these findings reveal a novel autolytic pathway in S. mutans which may be involved in the dissemination of fitness-enhancing genes in the oral biofilm.

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Maintaining cell envelope integrity is critical for bacterial survival, including bacteria living in a complex and dynamic environment such as the human oral cavity. Streptococcus mutans, a major etiological agent of dental caries, uses two-component signal transduction systems (TCSTSs) to monitor and respond to various environmental stimuli. Previous studies have shown that the LiaSR TCSTS in S. mutans regulates virulence traits such as acid tolerance and biofilm formation. Although not examined in streptococci, homologs of LiaSR are widely disseminated in Firmicutes and function as part of the cell envelope stress response network. We describe here liaSR and its upstream liaF gene in the cell envelope stress tolerance of S. mutans strain UA159. Transcriptional analysis established liaSR as part of the pentacistronic liaFSR-ppiB-pnpB operon. A survey of cell envelope antimicrobials revealed that mutants deficient in one or all of the liaFSR genes were susceptible to Lipid II cycle interfering antibiotics and to chemicals that perturbed the cell membrane integrity. These compounds induced liaR transcription in a concentration-dependent manner. Notably, under bacitracin stress conditions, the LiaFSR signaling system was shown to induce transcription of several genes involved in membrane protein synthesis, peptidoglycan biosynthesis, envelope chaperone/proteases, and transcriptional regulators. In the absence of an inducer such as bacitracin, LiaF repressed LiaR-regulated expression, whereas supplementing cultures with bacitracin resulted in derepression of liaSR. While LiaF appears to be an integral component of the LiaSR signaling cascade, taken collectively, we report a novel role for LiaFSR in sensing cell envelope stress and preserving envelope integrity in S. mutans.