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Caracterização bioquímica de interações proteína-proteína relacionadas com o mecanismo de quorum-sensing do Xanthomonas axonopodis pv citri; Characterization of protein-protein interactions important for the regulation of the quorum-sensing process in Xanthomonas axonopodis pv citri.

Andrade, Maxuel de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/07/2006 PT
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Parte da produção de fatores de virulência em bactérias do gênero Xanthomonas esta sob controle de um grupo de genes localizados no locus rpf (regulation of pathogenicity factors), que respondem ao aumento da densidade celular num processo chamado quorum sensing. Os genes que codificam as proteínas do sistema Rpf de Xanthomonas axonopodis pv citri (Xac) foram clonados no vetor pOBD por Alegria (2004), e usados como iscas em ensaios de dois híbridos, contra uma biblioteca de Xac clonada no vetor pOAD. Neste ensaio, foram observadas interações entre RpfC-RpfG, RpfC-RpfF, RpfF-RpfF e RpfC-CMF. O gene cmf tem um ortólogo, cuja função esta relacionada com o processo de quorum sensing em Dictyostelium. Para confirmar essas interações, RpfC e seus domínios, RpfG, RpfF e CMF foram expressas e purificadas, produzidos anticorpos, e foram efetuados ensaios de ligação in vitro. Em adição, o domínio HD-GYP de RpfG, que apresenta atividade de fosfodiesterase, também foi usado como isca no ensaio de dois híbridos. Interessantemente, a maioria de suas presas foi derivada de domínios GGDEF (diguanilato ciclase) de um grupo de proteínas de Xac. Em bactérias, muitos fenótipos, como a ativação da virulência, a formação de biofilme e a mobilidade...

Estudo da sinalização celular envolvendo a via do quorum-sensing e os segundos mensageiros c-diGMP e (p)ppGpp no fitopatógeno Xanthomonas axonopodis pv citri; Study of cell signaling pathways involving quorum-sensing and the second messengers c-diGMP and (p)ppGpp in the phytopathogen Xanthomonas axonopodis pv citri

Andrade, Maxuel de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/08/2011 PT
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66.83%
O fitopatógeno Xanthomonas axonopodis pv citri (XAC) é o agente causal do cancro em citros. O desenvolvimento da infecção depende do sucesso de XAC na colonização do hospedeiro. Para isso, além do sistema de secreção tipo III, que injeta efetores de virulência dentro da célula do hospedeiro, Xanthomonas também conta com o processo de quorum-sensing. O aumento da densidade celular em XCC (Xanthomonas campestris pv campestris) promove o acúmulo da molécula sinalizadora difusível (DSF) produzida por RpfF, que ativa o sistema de dois componentes formado pelas proteínas RpfC e RpfG, as quais transduzem o sinal de ativação para o fator de transcrição Clp (CAP Like Protein - homóloga da proteína CAP de E. coli). A proteína RpfG contém um domínio de fosfodiesterase conservado (HD-GYP) que regula a concentração de diGMP cíclico (c-diGMP), um segundo mensageiro bacteriano. Dessa forma o domínio HD-GYP atua contrapondo-se à atividade dos domínios diguanilato ciclases (GGDEF). No caso de XCC, foi demonstrado que a ativação do domínio HD-GYP de RpfG reduz a concentração de c-diGMP na célula e promove a ligação e ação positiva de Clp no promotor do gene de engXCA. Com intuito de estudar a via Rpf em XAC, produzimos mutantes não-polares de rpfF...

Um novo gene de Pseudomonas aeruginosa envolvido em percepção de quórum; A novel gene involved in Pseudomonas aeruginosa quorum sensing

Nascimento, Ana Paula Barbosa do
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/06/2014 PT
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66.67%
Pseudomonas aeruginosa é uma gamaproteobactéria com capacidade de colonizar diversos tipos de ambiente e infectar hospedeiros filogeneticamente distintos. Em humanos, comporta-se como um patógeno oportunista,estando frequentemente relacionada à infecções em indivíduos imunocomprometidos e indivíduos portadores de fibrose cística. Um mecanismo importante para a versatilidade de P. aeruginosa é o sistema de percepção de quórum (QS), onde a bactéria pode vincular expressão gênica à densidade populacional e às características do ambiente. Atualmente, sabe-se que muitos outros reguladores estão interligados com QS, entre eles, a proteína reguladora RsmA e os pequenos RNAs RsmZ e RsmY. Além disso, diversos fatores importantes para a patogenicidade da bactéria são reguladas por QS. Em P. aeruginosa PA14, um fator importante para a patogenicidade em diversos hospedeiros é a proteína KerV, cujo envolvimento com QS foi descrito pela primeira vez neste trabalho. A linhagem D12, que possui uma deleção no gene kerV, mostrou alterações em fenótipos regulados por QS, como a maior produção de piocianina, composto que contribui para virulência e persistência das infecções causada por P. aeruginosa. Por ser facilmente detectável e pela regulação de sua síntese não ter sido completamente explorada em PA14...

Enterobacter sakazakii (Cronobacter spp.) e Bacillus cereus : quorum sensing, formação de biofilme e ação de sanitizantes; Enterobacter sakazakii (Cronobacter spp.) and Bacillus cereus : quorum sensing, biofilm formation and efficacy of sanitizers

Luciana Maria Ramires Esper
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 06/04/2010 PT
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A contaminação de fórmulas infantis por Enterobacter sakazakii (Cronobacter spp.) e Bacillus cereus pode ter como origem o contato do alimento com biofilmes formados em ambientes, utensílios e equipamentos empregados na sua produção ou posterior reconstituição nos locais de distribuição. A grande preocupação em relação a estas bactérias é a presença das mesmas em fórmulas infantis, produtos estes utilizados como fonte de alimentação para lactentes de forma exclusiva ou em combinação com outros alimentos. A formação de biofilmes, assim como outros mecanismos celulares como por exemplo a produção de bacteriocinas e fatores de virulência, podem ser modulados pelo processo de comunicação célula-célula ou quorum sensing - mecanismo de sinalização célula-célula mediada pelo acúmulo de uma classe ou mais de moléculas sinalizadoras produzidas pela célula e excretadas para o meio externo. Por sua vez, a quebra deste sistema, pela degradação das moléculas sinalizadoras de comunicação, denomina-se quorum quenching. Neste trabalho objetivou-se, primeiramente, a avaliação da dinâmica de formação de biofilmes mono e multi-espécies de E. sakazakii (Cronobacter spp.) e B. cereus em superfície de aço inoxidável utilizando-se como meios de cultivos fórmula Infantil (FI) e caldo Luria Bertani (LB) e a eficácia de soluções de ácido peracético e de hipoclorito de sódio na inativação desses biofilmes. Outro objetivo principal foi pesquisar a ocorrência dos sistemas quorum sensing e quorum quenching em E. sakazakii (Cronobacter spp.) e B. cereus e a possível influência das moléculas sinalizadoras na sensibilidade destas bactérias aos antimicrobianos. A formação de biofilmes ocorreu de forma mais intensa ao utilizar-se a fórmula infantil...

Formação de biofilmes e produção de moléculas sinalizadoras de quorum sensing por cepas de Salmonellla spp. isoladas de processamento de frango; Biofilm formation and production of quorum sensing signaling molecules by strains of Salmonella spp. isolated from chicken processing

Maria Amelia de Jesus Piton
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/12/2012 PT
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Apesar da implantação de ferramentas e programas de controle para redução da incidência de Salmonella spp. nas granjas e abatedouros avícolas, a prevalência deste patógeno na cadeia produtiva avícola ainda é representativa. A adesão dos micro-organismos à superfície de equipamentos utilizados no processamento de alimentos resulta em graves problemas, pois atua como fonte de contaminação. Estes agregados de células com altas densidades populacionais presentes na superfície podem produzir moléculas sinalizadoras de quorum sensing responsáveis pela expressão de características fenotípicas específicas, dentre elas substâncias envolvidas na formação de biofilme. Uma vez instalado o biofilme, a resistência desses organismos aumenta, dificultando a ação dos sanitizantes, comprometendo a qualidade dos alimentos, além de aumentar os riscos à saúde pública. Um total de 65 cepas de Salmonella, sendo 39 isoladas de carcaças e cortes de frango e 26 isoladas de amostras de granjas, foi caracterizado quanto aos sorotipos e resistência a 24 antimicrobianos. O sorotipo Enteritidis foi o predominante representando 67,7% das cepas, seguido do sorotipo Newport com 7,7%. Um total de 10 padrões de resistência foi identificado...

Effect of Candida albicans and Candida dubliniensis planktonic/biofilm quorum sensing molecules on yeast morphogenesis

Henriques, Mariana; Martins, M.; Azeredo, Joana; Oliveira, Rosário
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2006 ENG
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One of the aims of this work was to study the effect of farnesol, a quorum sensing molecule for Candida albicans, on morphologic inhibition of Candida dubliniensis. The second goal of this work was to confirm if Candida dubliniensis also excreted quorum sensing molecules, on both planktonic and biofilm forms. The results clearly demonstrate that Candida dubliniensis undergoes morphological alterations triggered by farnesol. It was also found that supernatants of Candida dubliniensis and Candida albicans grown in both planktonic or biofilm forms contain molecules that are capable of suppressing pseudohyphae formation on Candida dubliniensis cells grown in RPMI 1640. It can be concluded that both Candida dubliniensis and Candida albicans produces quorum sensing molecules either in planktonic or biofilm forms, which regulates Candida dubliniensis morphology.

Mining quorum sensing in pathogenic P. aeruginosa and C. albicans

Santos, Nadine Castelhano
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em //2013 ENG
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66.78%
Dissertação de mestrado de Bionformática; O estudo do fenómeno de cross-talking entre P. aeruginosa e C. albicans tem sido focado essencialmente nos processos de quorum sensing e formação de biofilmes, identificando-se os genes e proteínas envolvidas. Contudo, mesmo já existindo um grande conhecimento dos genes e proteínas envolvidas, ainda existe uma lacuna na integração dos mesmos nas redes biológicas dos respectivos microorganismos. O número e qualidade das redes biológicas existentes (Transcriptional Regulatory Network - TRN and Protein-protein Interactions - PPI) para os fenómenos chave tais como, quorum sensing, formação de biofilmes, resistência a antibióticos e patogenecidade, não evidenciam a importância de alguns destes genes no fenómeno de crosstalking. Esta tese apresenta-se como a primeira tentativa de colocar em evidência os genes e proteínas envolvidos em cross-talking, associando-os aos parceiros de interacção nas respectivas redes biológicas de cada microorganismo. Primeiramente, utilizou-se um processo de integração de redes para os dois microrganismos, levando ao aumento do conhecimento geral sobre os processos de patogenecidade dos dois microorganismos, e por fim os genes envolvidos em cross-talking...

Lack of AHL-based quorum sensing in Pseudomonas fluorescens isolated from milk

Martins,Maurilio L.; Uelinton,M. Pinto; Riedel,Kathrin; Vanetti,Maria C.D.; Mantovani,Hilário C.; Araújo,Elza F. de
Fonte: Sociedade Brasileira de Microbiologia Publicador: Sociedade Brasileira de Microbiologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2014 EN
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66.69%
Numerous bacteria coordinate gene expression in response to small signalling molecules in many cases known as acylhomoserine lactones (AHLs), which accumulate as a function of cell density in a process known as quorum sensing. This work aimed to determine if phenotypes that are important to define microbial activity in foods such as biofilm formation, swarming motility and proteolytic activity of two Pseudomonas fluorescens strains, isolated from refrigerated raw milk, are influenced by AHL molecules. The tested P. fluorescens strains did not produce AHL molecules in none of the evaluated media. We found that biofilm formation was dependent on the culture media, but it was not influenced by AHLs. Our results indicate that biofilm formation, swarming motility and proteolytic activity of the tested P. fluorescens strains are not regulated by acyl-homoserine lactones. It is likely that AHL-dependent quorum sensing system is absent from these strains.

Efeito do Quorum Sensing na Motilidade e na Multiplica????o de Salmonella Typhimurium.; Effect of the Quorum Sensing on the Salmonella Typhimurium Growth and Motility

CONCEI????O, Rita de C??ssia dos Santos da
Fonte: Universidade Federal de Pelotas; Biotecnologia; Programa de P??s-Gradua????o em Biotecnologia; UFPel; BR Publicador: Universidade Federal de Pelotas; Biotecnologia; Programa de P??s-Gradua????o em Biotecnologia; UFPel; BR
Tipo: Tese de Doutorado Formato: application/pdf
POR
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Salmonella spp. is the most commonly bacterium transmitted through contamined food. The foods of animal are the most responsible for the worldwide distribution of this bacterium. Salmonella spp. is able to induce a variety of diseases, ranging from an enteric fever, septicemia, gastroenteritis and infections focused. This is due to the bacteria produce different pathogenicity factors and these factors, the flagellum was the target of our study and it is one of the pathogenicity factors induced by Quorum Sensing. Quorum Sensing is a bacterial signaling system that operates through the so-called autoinducer (AI). Gram-negative bacteria produce three auto-inducers. Studies find that catecholamines are able to use the same pathway the autoinducer 3 (AI-3) to active certain genes. Epinephrine and norepinephrine are catecholamines that are present in the mammalian gastrointestinal tract can modulate bacterial gene expression. This work had as objectives to evaluate the Quorum Sensing signaling system on motility, on the growth and flagellar assembly gene expression of Salmonella enterica serovar Typhimurium (ST) and do a review about pathogenicity factors of Salmonella spp. induced by Quorum Sensing. ST was exposed to different concentrations of epinephrine and conditioned medium and its association. The combination of 500 μM epinephrine with 50 % conditioned medium increased ST bacterial motility...

UTILIZA????O DO QUORUM SENSING NA EXPRESS??O DE ANT??GENOS VACINAIS EM Escherichia coli Enterotoxig??nica; THE USE OF QUORUM SENSING FOR EXPRESSION OF VACCINAL ANTIGENS OF Escherichia coli ENTEROTOXIGENIC

STURBELLE, R??gis Tuchtenhagen
Fonte: Universidade Federal de Pelotas; Biotecnologia; Programa de P??s-Gradua????o em Biotecnologia; UFPel; BR Publicador: Universidade Federal de Pelotas; Biotecnologia; Programa de P??s-Gradua????o em Biotecnologia; UFPel; BR
Tipo: Dissertação Formato: application/pdf
POR
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66.83%
One of the most important sanitary problems that cause economic losses in swine industry is the diarrhea caused by Enterotoxigenic Escherichia coli (ETEC). It is the main infectious cause of mortality for animals in suckling and post-weaning periods. Their primary factors of pathogenicity are the fimbriae, which bond the bacteria to specific receptors of the enterocytes. This causes a succession of events, brought about by the enterotoxins, the stable toxins (ST) and heat-labile toxins (LT), leading to diarrhea. Another important structure is the flagellum, which has an important role in cell stimulation to produce pro-inflammatory cytokines through the interaction with Toll-like receptors (TLR5), signaling cell recruitment and activation, thus increasing local inflammation as well as antigen presentation to lymphocytes. Quorum Sensing is a signaling system among bacteria that uses substances denominated autoinducers (AI). When the auto-inducers reach a certain concentration, due to an increase of cell density, there is an activation of transcriptional factors, which regulate the gene expression. The catecholamines (adrenaline and noradrenalin), produced by nervous cells, use the auto-inducer type 3 (AI-3) pathway. These have a significant role in gene expression as they stimulate the growth and the expression of virulence factors of the Escherichia coli. The goal of the present study was to produce experimental vaccines containing total cultures of ETEC cultivated in different induction conditions...

Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: Co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia

Chan, Kok-Gan; Atkinson, Steve; Mathee, Kalai; Sam, Choon-Kook; Chhabra, Siri Ram; Cámara, Miguel; Koh, Chong-Lek; Williams, Paul
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
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Background Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novelN-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest. Results By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the generaAcinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. Conclusions Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.

Anti-Quorum Sensing Agents from South Florida Medicinal Plants and their Attenuation of Pseudomonas Aeruginosa Pathogenicity

Adonizio, Allison L.
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
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With the difficulty in treating recalcitrant infections and the growing resistance to antibiotics, new therapeutic modalities are becoming increasingly necessary. The interruption of bacterial quorum sensing (QS), or cell-cell communication is known to attenuate virulence, while limiting selective pressure toward resistance. This study initiates an ethnobotanically-directed search for QS inhibiting agents in south Florida medicinal plants. Fifty plants were screened for anti-QS activity using two biomonitor strains, Chromobacterium violaceum and Agrobacterium tumefaciens. Of these plants, six showed QS inhibition: Conocarpus erectus L. (Combretaceae), Chamaecyce hypericifolia (L.) Millsp. (Euphorbiaceae), Callistemon viminalis (Sol.ex Gaertn.) G. Don (Myrtaceae), Bucida burceras L. (Combretaceae), Tetrazygia bicolor (Mill.) Cogn. (Melastomataceae), and Quercus virginiana Mill. (Fagaceae). These plants were further examined for their effects on the QS system and virulence of Pseudomonas aeruginosa, an intractable opportunistic pathogen responsible for morbidity and mortality in the immunocompromised patient. C. erectus, B. buceras, and C. viminalis were found to significantly inhibit multiple virulence factors and biofilm formation in this organism. Each plant presented a distinct profile of effect on QS genes and signaling molecules...

Mathematical modelling of quorum sensing in bacteria

Ward, J.; King, J.; Koerber, A.; Williams, P.; Croft, J.; Sockett, R.
Fonte: Oxford Univ Press Publicador: Oxford Univ Press
Tipo: Artigo de Revista Científica
Publicado em //2001 EN
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The regulation of density-dependent behaviour by means of quorum sensing is widespread in bacteria, the relevant phenomena including bioluminescence and population expansion by swarming, as well as virulence. The process of quorum sensing is regulated by the production and monitoring of certain molecules (referred to as QSMs); on reaching an apparent threshold concentration of QSMs (reflecting high bacterial density) the bacterial colony in concert ‘switches on’ the density-dependent trait. In this paper a mathematical model which describes bacterial population growth and quorum sensing in a well mixed system is proposed and studied. We view the population of bacteria as consisting of down-regulated and up-regulated sub-populations, with QSMs being produced at a much faster rate by the up-regulated cells. Using curve fitting techniques for parameter estimation, solutions of the resulting system of ordinary differential equations are shown to agree well with experimental data. Asymptotic analysis in a biologically relevant limit is used to investigate the timescales for up-regulation of an exponentially growing population of bacteria, revealing the existence of bifurcation between limited and near-total up-regulation. For a fixed population of cells steady-state analysis reveals that in general one physical steady-state solution exists and is linearly stable; we believe this solution to be a global attractor. A bifurcation between limited and near-total up-regulation is also discussed in the steady-state limit.; http://imammb.oxfordjournals.org/content/vol18/issue3/index.dtl; © 2001 by Institute of Mathematics and its Applications

A structural perspective on the mechanisms of quorum sensing activation in bacteria

LIXA,CAROLINA; MUJO,AMANDA; ANOBOM,CRISTIANE D.; PINHEIRO,ANDERSON S.
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
66.78%
Bacteria are able to synchronize the population behavior in order to regulate gene expression through a cell-to-cell communication mechanism called quorum sensing. This phenomenon involves the production, detection and the response to extracellular signaling molecules named autoinducers, which directly or indirectly regulate gene expression in a cell density-dependent manner. Quorum sensing may control a wide range of biological processes in bacteria, such as bioluminescence, virulence factor production, biofilm formation and antibiotic resistance. The autoinducers are recognized by specific receptors that can either be membrane-bound histidine kinase receptors, which work by activating cognate cytoplasmic response regulators, or cytoplasmic receptors acting as transcription factors. In this review, we focused on the cytosolic quorum sensing regulators whose three-dimensional structures helped elucidate their mechanisms of action. Structural studies of quorum sensing receptors may enable the rational design of inhibitor molecules. Ultimately, this approach may represent an effective alternative to treat infections where classical antimicrobial therapy fails to overcome the microorganism virulence.

Characterization of N-acylhomoserine lactone-degrading bacteria associated with the Zingiber officinale (ginger) rhizosphere: Co-existence of quorum quenching and quorum sensing in Acinetobacter and Burkholderia

Chan, Kok-Gan; Atkinson, Steve; Mathee, Kalai; Sam, Choon-Kook; Chhabra, Siri Ram; Cámara, Miguel; Koh, Chong-Lek; Williams, Paul
Fonte: SelectedWorks Publicador: SelectedWorks
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.67%
Background Cell-to-cell communication (quorum sensing (QS)) co-ordinates bacterial behaviour at a population level. Consequently the behaviour of a natural multi-species community is likely to depend at least in part on co-existing QS and quorum quenching (QQ) activities. Here we sought to discover novelN-acylhomoserine lactone (AHL)-dependent QS and QQ strains by investigating a bacterial community associated with the rhizosphere of ginger (Zingiber officinale) growing in the Malaysian rainforest. Results By using a basal growth medium containing N-(3-oxohexanoyl)homoserine lactone (3-oxo-C6-HSL) as the sole source of carbon and nitrogen, the ginger rhizosphere associated bacteria were enriched for strains with AHL-degrading capabilities. Three isolates belonging to the generaAcinetobacter (GG2), Burkholderia (GG4) and Klebsiella (Se14) were identified and selected for further study. Strains GG2 and Se14 exhibited the broadest spectrum of AHL-degrading activities via lactonolysis while GG4 reduced 3-oxo-AHLs to the corresponding 3-hydroxy compounds. In GG2 and GG4, QQ was found to co-exist with AHL-dependent QS and GG2 was shown to inactivate both self-generated and exogenously supplied AHLs. GG2, GG4 and Se14 were each able to attenuate virulence factor production in both human and plant pathogens. Conclusions Collectively our data show that ginger rhizosphere bacteria which make and degrade a wide range of AHLs are likely to play a collective role in determining the QS-dependent phenotype of a polymicrobial community.

Manipulation of the Quorum Sensing Signal AI-2 Affects the Antibiotic-Treated Gut Microbiota

Thompson, Jessica Ann; Oliveira, Rita Almeida; Djukovic, Ana; Ubeda, Carles; Xavier, Karina Bivar
Fonte: Cell Press Publicador: Cell Press
Tipo: Artigo de Revista Científica
Publicado em 24/03/2015 ENG
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66.64%
The mammalian gut microbiota harbors a diverse ecosystem where hundreds of bacterial species interact with each other and their host. Given that bacteria use signals to communicate and regulate group behaviors (quorum sensing), we asked whether such communication between different commensal species can influence the interactions occurring in this environment. We engineered the enteric bacterium, Escherichia coli, to manipulate the levels of the interspecies quorum sensing signal, autoinducer-2 (AI-2), in the mouse intestine and investigated the effect upon antibiotic-induced gut microbiota dysbiosis. E. coli that increased intestinal AI-2 levels altered the composition of the antibiotic-treated gut microbiota, favoring the expansion of the Firmicutes phylum. This significantly increased the Firmicutes/Bacteroidetes ratio, to oppose the strong effect of the antibiotic, which had almost cleared the Firmicutes. This demonstrates that AI-2 levels influence the abundance of the major phyla of the gut microbiota, the balance of which is known to influence human health.; Howard Hughes Medical Institute grants: (International Early Career Scientist, HHMI 55007436), Ministerio de Ciencia e Innovacion grants: (MICINN; SAF2011-29458), Marie-Curie Career Integration grant: (PCIG09-GA-2011-293894).

Development of polymeric materials to inhibit bacterial quorum sensing; Desenvolvimento de materiais poliméricos para inibição de quorum sensing

Cavaleiro, Eliana Marisa dos Santos
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
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Bacterial infections are an increasing problem for human health. In fact, an increasing number of infections are caused by bacteria that are resistant to most antibiotics and their combinations. Therefore, the scientific community is currently searching for new solutions to fight bacteria and infectious diseases, without promoting antimicrobial resistance. One of the most promising strategies is the disruption or attenuation of bacterial Quorum Sensing (QS), a refined system that bacteria use to communicate. In a QS event, bacteria produce and release specific small chemicals, signal molecules - autoinducers (AIs) - into the environment. At the same time that bacterial population grows, the concentration of AIs in the bacterial environment increases. When a threshold concentration of AIs is reached, bacterial cells respond to it by altering their gene expression profile. AIs regulate gene expression as a function of cell population density. Phenotypes mediated by QS (QSphenotypes) include virulence factors, toxin production, antibiotic resistance and biofilm formation. In this work, two polymeric materials (linear polymers and molecularly imprinted nanoparticles) were developed and their ability to attenuate QS was evaluated. Both types of polymers should to be able to adsorb bacterial signal molecules...

Fatty acid-mediated quorum sensing systems in stenotrophomonas maltophilia

Huedo Moreno, Pol
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2015 ENG
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Els sistemes de comunicació bacteriana -coneguts com quorum sensing (QS)- a través de molècules senyalitzadores del tipus àcid gras han despertat molt d'interès en els darrers anys ja que s'ha vist que molts bacteris patògens els utilitzen per regular funcions relacionades amb la virulència. Es coneix que Stenotrophomonas maltophilia presenta el sistema de QS DSF (Diffusible Signal Factor) el qual és controlat pels gens que conformen el clúster rpf (Regulation of Pathogenecity Factors). No obstant, no està clar els mecanismes pels quals S. maltophilia sintetitza i sensa les molècules senyal així com quines funcions estan regulades per aquest sistema. En aquest treball hem demostrat que existeixen dues poblacions de S. maltophilia les quals es diferencien en base al clúster rpf (rpf-1 o rpf-2) que presenten. Cada variant difereix bàsicament en els gens que codifiquen per la sintasa RpfF i el sensor RpfC. A més, hem observat que existeix una associació entre ambdós components, generant-se la parella RpfF-1/RpfC-1 per les soques rpf-1 i RpfF-2/RpfC-2 per les soques rpf-2. Addicionalment, hem demostrat que només aquelles soques que presenten la variant rpf-1 produeixen nivells detectables de DSF i aquest regula motilitat bacteriana...

Chlamydomonas reinhardtii secretes compounds that mimic bacterial signals and interfere with quorum sensing regulation in bacteria

Teplitski, Max; Chen, Hancai; Rajamani, S; Gao, Mengsheng; Merighi, M; Sayre, Richard T; Robinson, Jayne B; Rolfe, Barry; Bauer, Wolfgang
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
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The unicellular soil-freshwater alga Chlamydomonas reinhardtii was found to secrete substances that mimic the activity of the N-acyl-L-homoserine lactone (AHL) signal molecules used by many bacteria for quorum sensing regulation of gene expression. More than a dozen chemically separable but unidentified substances capable of specifically stimulating the LasR or CepR but not the LuxR, AhyR, or CviR AHL bacterial quorum sensing reporter strains were detected in ethyl acetate extracts of C. reinhardtii culture filtrates. Colonies of C. reinhardtii and Chlorella spp. stimulated quorum sensing-dependent luminescence in Vibrio harveyi, indicating that these algae may produce compounds that affect the AI-2 furanosyl borate diester-mediated quorum sensing system of Vibrio spp. Treatment of the soil bacterium Sinorhizobium meliloti with a partially purified LasR mimic from C. reinhardtii affected the accumulation of 16 of the 25 proteins that were altered in response to the bacterium's own AHL signals, providing evidence that the algal mimic affected quorum sensing-regulated functions in this wild-type bacterium. Peptide mass fingerprinting identified 32 proteins affected by the bacterium's AHLs or the purified algal mimic, including GroEL chaperonins...

Quorum sensing signal profile of Acinetobacter strains from nosocomial and environmental sources

González,R. H.; Dijkshoorn,L.; Van den Barselaar,M.; Nudel,C.
Fonte: Revista argentina de microbiología Publicador: Revista argentina de microbiología
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2009 EN
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A set of 43 strains corresponding to 20 classified and unclassified genomic Acinetobacter species was analyzed for the production of typical N-acyl homoserine lactone quorum sensing molecules in culture broths. A large percentage of the strains (74%) displayed quorum sensing signals that could be separated into three statistically significantly different chromatographic groups (p < 0.001) based on their retention factor in TLC, i.e. Rf1 (0.22 ± 0.02); Rf2 (0.40 ± 0.02) and Rf3 (0.54 ± 0.02). Noteworthy, 63% of the strains tested produced more than one quorum signal. The frequency of signal appearance was Rf3 > Rf2 > Rf1. None of the three signals could be specifically assigned to a particular species in the genus; furthermore, no distinction could be made between the quorum sensing signals secreted by typical opportunistic strains of the A. calcoaceticus-A. baumannii complex, isolated from patients, with respect to the other species of the genus, except for the Rf1 signal which was present in all the QS positive strains belonging to this complex and DNA group 13 TU. In conclusion, quorum sensors in Acinetobacter are not homogenously distributed among species and one of them is present in most of the A. calcoaceticus-baumannii complex.