http://hdl.handle.net/10033/6876 Fri, 24 May 2013 19:05:33 GMT 2013-05-24T19:05:33Z http://hdl.handle.net/10033/254117 Title: The pseudomonas quinolone signal (PQS) balances life and death in Pseudomonas aeruginosa populations. Authors: Häussler, Susanne; Becker, Tanja Abstract: When environmental conditions deteriorate and become inhospitable, generic survival strategies for populations of bacteria may be to enter a dormant state that slows down metabolism, to develop a general tolerance to hostile parameters that characterize the habitat, and to impose a regime to eliminate damaged members. Here, we provide evidence that the pseudomonas quinolone signal (PQS) mediates induction of all of these phenotypes. For individual cells, PQS, an interbacterial signaling molecule of Pseudomonas aeruginosa, has both deleterious and beneficial activities: on the one hand, it acts as a pro-oxidant and sensitizes the bacteria towards oxidative and other stresses and, on the other, it efficiently induces a protective anti-oxidative stress response. We propose that this dual function fragments populations into less and more stress tolerant members which respond differentially to developing stresses in deteriorating habitats. This suggests that a little poison may be generically beneficial to populations, in promoting survival of the fittest, and in contributing to bacterial multi-cellular behavior. It further identifies PQS as an essential mediator of the shaping of the population structure of Pseudomonas and of its response to and survival in hostile environmental conditions. Tue, 01 Jan 2008 00:00:00 GMT http://hdl.handle.net/10033/254117 2008-01-01T00:00:00Z http://hdl.handle.net/10033/237935 Title: Phenotypic and genome-wide analysis of an antibiotic-resistant small colony variant (SCV) of Pseudomonas aeruginosa. Authors: Wei, Qing; Tarighi, Saeed; Dötsch, Andreas; Häussler, Susanne; Müsken, Mathias; Wright, Victoria J; Cámara, Miguel; Williams, Paul; Haenen, Steven; Boerjan, Bart; Bogaerts, Annelies; Vierstraete, Evy; Verleyen, Peter; Schoofs, Liliane; Willaert, Ronnie; De Groote, Valérie N; Michiels, Jan; Vercammen, Ken; Crabbé, Aurélie; Cornelis, Pierre Abstract: Small colony variants (SCVs) are slow-growing bacteria, which often show increased resistance to antibiotics and cause latent or recurrent infections. It is therefore important to understand the mechanisms at the basis of this phenotypic switch. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10033/237935 2011-01-01T00:00:00Z http://hdl.handle.net/10033/145689 Title: Acquired type III secretion system determines environmental fitness of epidemic Vibrio parahaemolyticus in the interaction with bacterivorous protists. Authors: Matz, Carsten; Nouri, Bianka; McCarter, Linda; Martinez-Urtaza, Jaime Abstract: Genome analyses of marine microbial communities have revealed the widespread occurrence of genomic islands (GIs), many of which encode for protein secretion machineries described in the context of bacteria-eukaryote interactions. Yet experimental support for the specific roles of such GIs in aquatic community interactions remains scarce. Here, we test for the contribution of type III secretion systems (T3SS) to the environmental fitness of epidemic Vibrio parahaemolyticus. Comparisons of V. parahaemolyticus wild types and T3SS-defective mutants demonstrate that the T3SS encoded on genome island VPaI-7 (T3SS-2) promotes survival of V. parahaemolyticus in the interaction with diverse protist taxa. Enhanced persistence was found to be due to T3SS-2 mediated cytotoxicity and facultative parasitism of V. parahaemolyticus on coexisting protists. Growth in the presence of bacterivorous protists and the T3SS-2 genotype showed a strong correlation across environmental and clinical isolates of V. parahaemolyticus. Short-term microcosm experiments provide evidence that protistan hosts facilitate the invasion of T3SS-2 positive V. parahaemolyticus into a coastal plankton community, and that water temperature and productivity further promote enhanced survival of T3SS-2 positive V. parahaemolyticus. This study is the first to describe the fitness advantage of GI-encoded functions in a microbial food web, which may provide a mechanistic explanation for the global spread and the seasonal dynamics of V. parahaemolyticus pathotypes, including the pandemic serotype cluster O3:K6, in aquatic environments. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10033/145689 2011-01-01T00:00:00Z http://hdl.handle.net/10033/128811 Title: The Pseudomonas aeruginosa Chemotaxis Methyltransferase CheR1 Impacts on Bacterial Surface Sampling. Authors: Schmidt, Juliane; Müsken, Mathias; Becker, Tanja; Magnowska, Zofia; Bertinetti, Daniela; Möller, Stefan; Zimmermann, Bastian; Herberg, Friedrich W; Jänsch, Lothar; Häussler, Susanne Abstract: The characterization of factors contributing to the formation and development of surface-associated bacterial communities known as biofilms has become an area of intense interest since biofilms have a major impact on human health, the environment and industry. Various studies have demonstrated that motility, including swimming, swarming and twitching, seems to play an important role in the surface colonization and establishment of structured biofilms. Thereby, the impact of chemotaxis on biofilm formation has been less intensively studied. Pseudomonas aeruginosa has a very complex chemosensory system with two Che systems implicated in flagella-mediated motility. In this study, we demonstrate that the chemotaxis protein CheR1 is a methyltransferase that binds S-adenosylmethionine and transfers a methyl group from this methyl donor to the chemoreceptor PctA, an activity which can be stimulated by the attractant serine but not by glutamine. We furthermore demonstrate that CheR1 does not only play a role in flagella-mediated chemotaxis but that its activity is essential for the formation and maintenance of bacterial biofilm structures. We propose a model in which motility and chemotaxis impact on initial attachment processes, dispersion and reattachment and increase the efficiency and frequency of surface sampling in P. aeruginosa. Sat, 01 Jan 2011 00:00:00 GMT http://hdl.handle.net/10033/128811 2011-01-01T00:00:00Z