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Avaliação da capacidade de formação de biofilme por Acinetobacter baumannii e perfil transcricional de genes envolvidos nesse processo; Evaluation of the capacity to form biofilm by Acinetobacter baumannii and transcriptional profiling of genes involved on this processes

Bierhals, Christine Garcia
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
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26.95%
Acinetobacter baumannii é um patógeno oportunista, geralmente resistente a muitos antimicrobianos, que causa surtos de infecções hospitalares. Assim, a sua habilidade de formar biofilme pode explicar a capacidade de sobreviver no ambiente hospitalar e em utensílios médicos. O objetivo desse estudo foi avaliar a capacidade de duas cepas clínicas de A. baumannii obtido de hospitais de Porto Alegre, Brasil (abC e abH) e uma cepa controle ATCC 19606 (abA) formar biofilme e realizar a análise transcricional dos genes possivelmente envolvidos na produção e manutenção do biofilme: bap, abaI, ompA, bfmRS, csuAB, pgaA, pilZ, wspR, eal, eagg, IscRSU e csdA. A capacidade de formação de biofilme foi avaliada pelo método cristal violeta em superfície plástica a 25°C e 37°C nos meios LB, LB + 1% glicose, urina pura e LB + 10% sangue de carneiro. A análise transcricional foi feita por real time PCR. A cepas AbH, AbC e AbA foram fortes formadoras de biofileme em LB e LB+glicose à 25 e 37°C. Em LB+sangue, as cepas AbH e AbA foram fortes formadoras e AbC foi fraca formadora de biofilme. Em urina, a cepa AbH foi moderadamente formadora, AbC e AbA foram fracas formadoras de biofilme. Os genes wspR, pgaA, ompA, bap, abaI de AbA, csdA de AbH e o operon IscRSU foram superexpressos em biofilme; os genes eagg de AbH...

Analise dos efeitos da interação entre S mutans e materiais restauradores esteticos : caracteristicas do biofilme em microscopio confocal de varredura a laser e propriedades de superficie dos materiais apos 30 dias; Analysis of the interaction between S. mutans and esthetic restorative materials : biofilm chracteristics by confocal laser scanning microscopy and material surface properties after 30 days

Suzana Beatriz Portugal de Fucio
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/02/2007 PT
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O desenvolvimento do biofilme de Streptococcus mutans sobre materiais restauradores e a biodegradação destes substratos em função dos metabólitos bacterianos podem ser influenciados pelas propriedades e características do material. A partir de uma revisão sistemática em que se verificou a carência de estudos a respeito dos efeitos do biofilme na superfície de materiais restauradores, foi proposto investigar algumas características quantitativas e qualitativas do biofilme após 30 dias de interação com materiais restauradores, além de analisar propriedades e microestrutura da superfície dos materiais que sofreram tal interação. Para cada material testado (cerâmica - C, resina composta nanoparticulada ? RC e cimentos de ionômero de vidro modificado por resina - CIVMR e convencional - CIVC), foram confeccionados 25 discos sob condições assépticas, para distribuição em 3 grupos de estocagem: 1) 100% de umidade relativa a 37ºC (n=5); 2) meio de cultura a 37ºC (BHI + 1% sacarose) (n=5); 3) biofilme de Streptococcus mutans e meio de cultura a 37ºC (n=15). Valores de dureza do grupo 1 (valores imediatos) foram obtidos previamente à estocagem, a fim de se verificar alterações ao longo do tempo quando estocados em umidade relativa apenas. Após 30 dias de estocagem...

Envolvimento dos genes qseC e sdiA na formação de biofilme por Escherichia coli enteropatogênica atípica; Influence of qseC and sdiA gene in biofilm formation by atypical enteropathogenic Escherichia coli

Hebert Fabricio Culler
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 20/01/2015 PT
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As Escherichia coli enteropatogênicas atípicas são capazes de formar biofilme em superfícies abióticas e bióticas. Diversos mecanismos em E. coli são regulados por Quorum Sensing, incluindo a expressão de fatores de virulência e formação de biofilme. Quorum Sensing é um sistema de sinalização que confere às bactérias a habilidade de responder à moléculas químicas denominadas autoindutores (AI). SdiA e QseC são receptores de quorum sensing encontrados em diversas bactérias, entre elas EPECa. SdiA detecta moléculas autoindutoras do tipo 1 (AI-1) denominadas N-acil homoserina lactonas (AHLs). Entretanto as Escherichia coli não possuem a sintase para estas moléculas e, deste modo, SdiA detecta AHLs produzidas por outras bactérias. O receptor QseC detecta moléculas autoindutoras do tipo 3, além dos hormônios humanos adrenalina e noradrenalina. Neste estudo verificamos a influência da deleção de sdiA e qseC na formação e arquitetura do biofilme, formação de película, anel e também na transcrição de alguns dos genes envolvidos nestes fenótipos (bcsA, csgA, csgD, fliC, fimA e rpoS) em duas amostras de EPECa, sendo uma do sorotipo O55:H7 e outra do sorotipo ONT:H25. Os resultados das análises nas duas amostras de EPECa foram distintos...

Effect of mechanical stress on biofilms challenged by different chemicals

Simões, M.; Pereira, Maria Olívia; Vieira, M. J.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em /12/2005 ENG
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In this study a methodology was applied in order to ascertain the mechanical stability of biofilms, by using a stainlesssteel (SS) rotating device immersed in a biological reactor where biofilms formed by Pseudomonas fluorescens were allowed to grow for 7 days at a Reynolds number of agitation of 2400. The biofilms developed with this system were characterised in terms of amount of total, extracellular and intracellular proteins and polysaccharides, amount of mass, metabolic activity and mechanical stability, showing that the biofilms were active, had a high content of extracellular constituents and an inherent mechanical stability. In order to assess the role of chemical agents on the mechanical stability, the biofilms were exposed to chemical agents followed by mechanical treatments by submission to increase Reynolds number of agitation. Seven different chemical agents were tested (two non-oxidising biocides, three surfactants and two oxidising biocides) and their effects on the biofilm mechanical stability were evaluated. The increase in the Reynolds number increased the biofilm removal, but total biofilm removal was not found for all the conditions tested. For the experiment without chemical addition (only mechanical treatment)...

Comparative antibody-mediated phagocytosis of Staphylococcus epidermidis cells grown in a biofilm or in the planktonic state

Cerca, Nuno; Jefferson, Kimberly K.; Oliveira, Rosário; Pier, Gerald B.; Azeredo, Joana
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
26.95%
Staphylococcus epidermidis is an important cause of nosocomial infections. Virulence is attributable to elaboration of biofilms on medical surfaces that protect the organisms from immune system clearance. Even though leukocytes can penetrate biofilms, they fail to phagocytose and kill bacteria. The properties that make biofilm bacteria resistant to the immune system are not well characterized. In order to better understand the mechanisms of resistance of bacteria in biofilms to the immune system, we evaluated antibody penetration throughout the biofilm and antibody-mediated phagocytic killing of planktonic versus biofilm cells of S. epidermidis by using a rabbit antibody to poly-N-acetylglucosamine (PNAG). These antibodies are opsonic and protect against infection with planktonic cells of PNAG-positive Staphylococcus aureus and S. epidermidis. Antibody to PNAG readily penetrated the biofilm and bound to the same areas in the biofilm as did wheat germ agglutinin, a lectin known to bind to components of staphylococcal biofilms. However, biofilm cells were more resistant to opsonic killing than their planktonic counterparts in spite of producing more PNAG per cell than planktonic cells. Biofilm extracts inhibited opsonic killing mediated by antibody to PNAG...

Game and player : C. albicans biofilm lifestyle and extracellular DNA

Martins, Margarida; Uppuluri, Priya; Thomas, Derek P.; Cleary, Ian A.; Henriques, Mariana; Lopez-Ribot, José L.; Oliveira, Rosário
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2010 ENG
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DNA is as a structural component of bacterial biofilms extracellular matrix (ECM). Although evidences have shown that DNA may play a role in C. albicans biofilms, further studies are required to understand the contribution of extracellular DNA (eDNA) in C. albicans biofilm lifestyle. Herein we aimed to determine the eDNA content of C. albicans SC5314 biofilm ECM and the effect of DNase I and exogenous DNA treatments on biofilm formation and biofilm cells susceptibility to antifungals. First, for eDNA estimation in C. albicans biofilm ECM, biofilms were formed under flow conditions for 48 h. ECM was isolated and its DNA and protein contents were determined. Second, DNase (0.02 - 2 mg/ml) and exogenous DNA (10 - 2560 ng/ml) were added at different stages of biofilm development (microtiter plate model under static conditions). The effect of 24 h treatments was evaluated in terms of biofilm biomass by crystal violet assay (A550). Third, for antifungal testing, biofilms (in 96-well plates) were challenged with amphotericin B (0.06 - 16 mg/l), caspofungin (0.008 to 2 mg/l), and fluconazole (4 - 1024 mg/l) alone or in combination with DNase (0.125 mg/ml) or exogenous DNA (320 ng/ml). Sessile minimum inhibitory concentrations (SMIC) were determined at 80 % inhibition compared to drug-free controls using the XTT reduction assay. RPMI medium was used in all the assays. On one hand...

Listeria monocytogenes and salmonella enterica adhesion, biofilm formation and control

Rodrigues, Diana
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 15/11/2010 POR
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Food contamination leads to wide economic loss and has a strong impact on public health worldwide. Listeria monocytogenes and Salmonella enterica Enteritidis are two of the most sight threatening and frequent foodborne pathogens, being responsible for listeriosis and salmonellosis foodborne outbreaks, respectively. The work presented in this thesis aimed at investigating adhesion and biofilm formation ability of these two bacteria regarding yet unexplored growth conditions and exposure to antimicrobials, as well as study possible repercussions of chemical disinfection on the genetic expression of virulence factors and stress response by surviving biofilm cells. L. monocytogenes has been a polemic bacterium as far as its biofilm formation capability is concerned, with different, and sometimes controversial, conclusions being stated by several authors. After testing this biological process under batch and fed-batch growth modes, both previously used by several authors but never compared simultaneously before, the results herein presented showed that the different growth modes influenced biofilm formation by L. monocytogenes on polystyrene, both in terms of biofilms’ total biomass and cellular viability. Temperature also played an important role on L. monocytogenes biofilm formation since refrigeration temperatures led to biofilms with less biomass but highly metabolic active...

Small colony variants in biofilm population is not strictly required for biofilm resistance and persistence

Sousa, Ana Margarida; Rodrigues, Alícia; Pereira, Maria Olívia
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
26.95%
Pseudomonas aeruginosa is a well-known opportunistic pathogen, responsible for high mortality in several human infections. Such infection success is partly due to its phenotypic plasticity to switch to “fitter” phenotypes, such as small colony variants (SCV), generally associated to increased antibiotic resistance, and biofilm formation within the human body. Once embedded in biofilms, P. aeruginosa can augment its pathogenicity and improve its ability to survive to stressful conditions, such immune defenses and antibiotics action. Moreover, the presence of SCV in biofilms has been pointed out as a biofilm mechanism responsible for its antibiotic resistance and persistence in human body. Regarding the impact of P. aeruginosa biofilms in disease management, it was considered crucial to determine the role of SCV in biofilm population and to study its correlation with antibiotic resistance and biofilm persistence ability. This study used several P. aeruginosa strains to form distinct biofilms in order to assess their antibiotic susceptibility to ciprofloxacin and colistin, virulence factors expression of biofilm-associated bacteria and to determine the presence and prevalence of SCV in biofilm population. The results obtained revealed that SCV presence in biofilm population is not strictly associated with biofilm antibiotic resistance. P. aeruginosa PAI2 demonstrated augmented resistance to both antibiotics...

Microbiological Evaluation of a Range of Disinfectant Products To Control Mixed-Species Biofilm Contamination in a Laboratory Model of a Dental Unit Water System

Walker, J. T.; Bradshaw, D. J.; Fulford, M. R.; Marsh, P. D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2003 EN
Relevância na Pesquisa
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Dental unit water system (DUWS) tubing harbors complex multispecies biofilms that are responsible for high microbial levels at the distal outlet. The aim of this study was to use an established biofilm laboratory model to simulate biofouling of DUWS to evaluate practical, cost-effective, and evidence-based methods of microbial decontamination. Reproducible biofilms were developed in the model over 14 days; decontamination was assessed using total viable counts (TVC) and microscopic-image analysis techniques to view the inner surface of tubing. Flushing did not reduce the biofilm coverage or TVC. Combizyme and ozone did not completely eliminate the viable bacteria (70 and 65% reduction in biofilm TVC, respectively), nor did they remove the biofilm (45 and 57% reduction in biofilm coverage, respectively). Chlorhexidine and Bio2000 (active agent: ethanol and chlorhexidine), Tegodor and Gigasept Rapid (aldehyde based), and Grotanol (hydroxide based) completely eliminated the TVC but did not completely remove biofilm (31, 53 33, 34, and 64.9% reduction of biofilm coverage, respectively). Other products including Grotanol Flussig (phenol based), Betadine (povidone-iodine based), Alpron (chlorite based), and the hydroxide-containing products Sporklenz...

Variation in Biofilm Formation among Strains of Listeria monocytogenes

Borucki, Monica K.; Peppin, Jason D.; White, David; Loge, Frank; Call, Douglas R.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2003 EN
Relevância na Pesquisa
26.95%
Contamination of food by Listeria monocytogenes is thought to occur most frequently in food-processing environments where cells persist due to their ability to attach to stainless steel and other surfaces. Once attached these cells may produce multicellular biofilms that are resistant to disinfection and from which cells can become detached and contaminate food products. Because there is a correlation between virulence and serotype (and thus phylogenetic division) of L. monocytogenes, it is important to determine if there is a link between biofilm formation and disease incidence for L. monocytogenes. Eighty L. monocytogenes isolates were screened for biofilm formation to determine if there is a robust relationship between biofilm formation, phylogenic division, and persistence in the environment. Statistically significant differences were detected between phylogenetic divisions. Increased biofilm formation was observed in Division II strains (serotypes 1/2a and 1/2c), which are not normally associated with food-borne outbreaks. Differences in biofilm formation were also detected between persistent and nonpersistent strains isolated from bulk milk samples, with persistent strains showing increased biofilm formation relative to nonpersistent strains. There were no significant differences detected among serotypes. Exopolysaccharide production correlated with cell adherence for high-biofilm-producing strains. Scanning electron microscopy showed that a high-biofilm-forming strain produced a dense...

Esp-Independent Biofilm Formation by Enterococcus faecalis

Kristich, Christopher J.; Li, Yung-Hua; Cvitkovitch, Dennis G.; Dunny, Gary M.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/2004 EN
Relevância na Pesquisa
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Enterococcus faecalis is a gram-positive opportunistic pathogen known to form biofilms in vitro. In addition, this organism is often isolated from biofilms on the surfaces of various indwelling medical devices. However, the molecular mechanisms regulating biofilm formation in these clinical isolates are largely unknown. Recent work has suggested that a specific cell surface protein (Esp) of E. faecalis is critical for biofilm formation by this organism. However, in the same study, esp-deficient strains of E. faecalis were found to be capable of biofilm formation. To test the hypothesis that Esp is dispensable for biofilm formation by E. faecalis, we used microtiter plate assays and a chemostat-based biofilm fermentor assay to examine biofilm formation by genetically well-defined, non-Esp-expressing strains. Our results demonstrate that in vitro biofilm formation occurs, not only in the absence of esp, but also in the absence of the entire pathogenicity island that harbors the esp coding sequence. Using scanning electron microscopy to evaluate biofilms of E. faecalis OG1RF grown in the fermentor system, biofilm development was observed to progress through multiple stages, including attachment of individual cells to the substratum, microcolony formation...

Nontypeable Haemophilus influenzae Strain 2019 Produces a Biofilm Containing N-Acetylneuraminic Acid That May Mimic Sialylated O-Linked Glycans

Greiner, L. L.; Watanabe, H.; Phillips, N. J.; Shao, J.; Morgan, A.; Zaleski, A.; Gibson, B. W.; Apicella, M. A.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/2004 EN
Relevância na Pesquisa
26.95%
Previous studies suggested that nontypeable Haemophilus influenzae (NTHI) can form biofilms during human and chinchilla middle ear infections. Microscopic analysis of a 5-day biofilm of NTHI strain 2019 grown in a continuous-flow chamber revealed that the biofilm had a diffuse matrix interlaced with multiple water channels. Our studies showed that biofilm production was significantly decreased when a chemically defined medium lacking N-acetylneuraminic acid (sialic acid) was used. Based on these observations, we examined mutations in seven NTHI strain 2019 genes involved in carbohydrate and lipooligosaccharide biosynthesis. NTHI strain 2019 with mutations in the genes encoding CMP-N-acetylneuraminic acid synthetase (siaB), one of the three NTHI sialyltransferases (siaA), and the undecaprenyl-phosphate α-N-acetylglucosaminyltransferase homolog (wecA) produced significantly smaller amounts of biofilm. NTHI strain 2019 with mutations in genes encoding phosphoglucomutase (pgm), UDP-galactose-4-epimerase, and two other NTHI sialyltransferases (lic3A and lsgB) produced biofilms that were equivalent to or larger than the biofilms produced by the parent strain. The biofilm formed by the NTHI strain 2019pgm mutant was studied with Maackia amurensis fluorescein isothiocyanate (FITC)-conjugated and Sambucus nigra tetramethyl rhodamine isocyanate (TRITC)-conjugated lectins. S. nigra TRITC-conjugated lectin bound to this biofilm...

Regulatory Role of Glycerol in Candida albicans Biofilm Formation

Desai, Jigar V.; Bruno, Vincent M.; Ganguly, Shantanu; Stamper, Ronald J.; Mitchell, Kaitlin F.; Solis, Norma; Hill, Elizabeth M.; Xu, Wenjie; Filler, Scott G.; Andes, David R.; Fanning, Saranna; Lanni, Frederick; Mitchell, Aaron P.
Fonte: American Society of Microbiology Publicador: American Society of Microbiology
Tipo: Artigo de Revista Científica
Publicado em 09/04/2013 EN
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26.96%
Biofilm formation by Candida albicans on medically implanted devices poses a significant clinical challenge. Here, we compared biofilm-associated gene expression in two clinical C. albicans isolates, SC5314 and WO-1, to identify shared gene regulatory responses that may be functionally relevant. Among the 62 genes most highly expressed in biofilms relative to planktonic (suspension-grown) cells, we were able to recover insertion mutations in 25 genes. Twenty mutants had altered biofilm-related properties, including cell substrate adherence, cell-cell signaling, and azole susceptibility. We focused on one of the most highly upregulated genes in our biofilm proles, RHR2, which specifies the glycerol biosynthetic enzyme glycerol-3-phosphatase. Glycerol is 5-fold-more abundant in biofilm cells than in planktonic cells, and an rhr2Δ/Δ strain accumulates 2-fold-less biofilm glycerol than does the wild type. Under in vitro conditions, the rhr2Δ/Δ mutant has reduced biofilm biomass and reduced adherence to silicone. The rhr2Δ/Δ mutant is also severely defective in biofilm formation in vivo in a rat catheter infection model. Expression profiling indicates that the rhr2Δ/Δ mutant has reduced expression of cell surface adhesin genes ALS1...

Biophysics of Biofilm Infection

Stewart, Philip S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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This article examines a likely basis of the tenacity of biofilm infections that has received relatively little attention: the resistance of biofilms to mechanical clearance. One way that a biofilm infection persists is by withstanding the flow of fluid or other mechanical forces that work to wash or sweep microorganisms out of the body. The fundamental criterion for mechanical persistence is that the biofilm failure strength exceeds the external applied stress. Mechanical failure of the biofilm and release of planktonic microbial cells is also important in vivo because it can result in dissemination of infection. The fundamental criterion for detachment and dissemination is that the applied stress exceeds the biofilm failure strength. The apparent contradiction for a biofilm to both persist and disseminate is resolved by recognizing that biofilm material properties are inherently heterogeneous. There are also mechanical aspects to the ways that infectious biofilms evade leukocyte phagocytosis. The possibility of alternative therapies for treating biofilm infections that work by reducing biofilm cohesion could: 1) allow prevailing hydrodynamic shear to remove biofilm, 2) increase the efficacy of designed interventions for removing biofilms...

Fluorescence-Based Quasicontinuous and In Situ Monitoring of Biofilm Formation Dynamics in Natural Marine Environments

Fischer, M.; Friedrichs, G.; Lachnit, T.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2014 EN
Relevância na Pesquisa
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Analyzing the dynamics of biofilm formation helps to deepen our understanding of surface colonization in natural environments. While methods for screening biofilm formation in the laboratory are well established, studies in marine environments have so far been based upon destructive analysis of individual samples and provide only discontinuous snapshots of biofilm establishment. In order to explore the development of biofilm over time and under various biotic and abiotic conditions, we applied a recently developed optical biofilm sensor to quasicontinuously analyze marine biofilm dynamics in situ. Using this technique in combination with microscope-assisted imaging, we investigated biofilm formation from its beginning to mature multispecies biofilms. In contrast to laboratory studies on biofilm formation, a smooth transition from initial attachment to colony formation and exponential growth could not be observed in the marine environment. Instead, initial attachment was followed by an adaptation phase of low growth and homogeneously distributed solitary bacterial cells. Moreover, we observed a diurnal variation of biofilm signal intensity, suggesting a transient state of biofilm formation of bacteria. Overall, the biofilm formation dynamics could be modeled by three consecutive development stages attributed to initial bacterial attachment...

Involvement of Stress-Related Genes polB and PA14_46880 in Biofilm Formation of Pseudomonas aeruginosa

Alshalchi, Sahar A.; Anderson, Gregory G.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2014 EN
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Chronic infections of Pseudomonas aeruginosa are generally established through production of biofilm. During biofilm formation, production of an extracellular matrix and establishment of a distinct bacterial phenotype make these infections difficult to eradicate. However, biofilm studies have been hampered by the fact that most assays utilize nonliving surfaces as biofilm attachment substrates. In an attempt to better understand the mechanisms behind P. aeruginosa biofilm formation, we performed a genetic screen to identify novel factors involved in biofilm formation on biotic and abiotic surfaces. We found that deletion of genes polB and PA14_46880 reduced biofilm formation significantly compared to that in the wild-type strain PA14 in an abiotic biofilm system. In a biotic biofilm model, wherein biofilms form on cultured airway cells, the ΔpolB and ΔPA14_46880 strains showed increased cytotoxic killing of the airway cells independent of the total number of bacteria bound. Notably, deletion mutant strains were more resistant to ciprofloxacin treatment. This phenotype was linked to decreased expression of algR, an alginate transcriptional regulatory gene, under ciprofloxacin pressure. Moreover, we found that pyocyanin production was increased in planktonic cells of mutant strains. These results indicate that inactivation of polB and PA14_46880 may inhibit transition of P. aeruginosa from a more acute infection lifestyle to the biofilm phenotype. Future investigation of these genes may lead to a better understanding of P. aeruginosa biofilm formation and chronic biofilm infections.

Biofilm growth mode promotes maximum carrying capacity and community stability during product inhibition syntrophy

Brileya, Kristen A.; Camilleri, Laura B.; Zane, Grant M.; Wall, Judy D.; Fields, Matthew W.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 15/12/2014 EN
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26.96%
Sulfate-reducing bacteria (SRB) can interact syntrophically with other community members in the absence of sulfate, and interactions with hydrogen-consuming methanogens are beneficial when these archaea consume potentially inhibitory H2 produced by the SRB. A dual continuous culture approach was used to characterize population structure within a syntrophic biofilm formed by the SRB Desulfovibrio vulgaris Hildenborough and the methanogenic archaeum Methanococcus maripaludis. Under the tested conditions, monocultures of D. vulgaris formed thin, stable biofilms, but monoculture M. maripaludis did not. Microscopy of intact syntrophic biofilm confirmed that D. vulgaris formed a scaffold for the biofilm, while intermediate and steady-state images revealed that M. maripaludis joined the biofilm later, likely in response to H2 produced by the SRB. Close interactions in structured biofilm allowed efficient transfer of H2 to M. maripaludis, and H2 was only detected in cocultures with a mutant SRB that was deficient in biofilm formation (ΔpilA). M. maripaludis produced more carbohydrate (uronic acid, hexose, and pentose) as a monoculture compared to total coculture biofilm, and this suggested an altered carbon flux during syntrophy. The syntrophic biofilm was structured into ridges (∼300 × 50 μm) and models predicted lactate limitation at ∼50 μm biofilm depth. The biofilm had structure that likely facilitated mass transfer of H2 and lactate...

A sigma factor and anti-sigma factor that control swarming motility and biofilm formation in Pseudomonas aeruginosa

McGuffie, Bryan A.
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
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Pseudomonas aeruginosa is an environmental bacterium and opportunistic human pathogen of major clinical significance. It is the principal cause of morbidity and mortality in patients with cystic fibrosis (CF) and a leading cause of nosocomial infections. Although the organism is unicellular, P. aeruginosa exhibits two forms of multicellular behaviors when associated with a surface under the right conditions: swarming motility and biofilm formation. Swarming motility is a multicellular cooperative form of flagella-dependent surface motility, while biofilm formation produces a sessile community of bacteria enclosed by a self-produced extracellular polymeric matrix. P. aeruginosa is thought to grow as a biofilm in the lungs of CF patients and the growth of P. aeruginosa biofilms on indwelling medical devices, such as endotracheal tubes and catheters, is a significant source of nosocomial infection. By growing as a biofilm, P. aeruginosa resists clearance by the immune system and increases its resistance to antimicrobial therapy. In this thesis, I describe the characterization of a sigma factor and anti-sigma factor implicated in P. aeruginosa virulence and cell envelope stress that control the expression of a novel regulator of swarming motility and biofilm formation. In addition...

Quantifying diffusion in biofilms : from model hydrogels to living biofilms

Golmohamadi, Mahmood
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
EN
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Les biofilms sont des communautés de microorganismes incorporés dans une matrice exo-polymérique complexe. Ils sont reconnus pour jouer un rôle important comme barrière de diffusion dans les systèmes environnementaux et la santé humaine, donnant lieu à une résistance accrue aux antibiotiques et aux désinfectants. Comme le transfert de masse dans un biofilm est principalement dû à la diffusion moléculaire, il est primordial de comprendre les principaux paramètres influençant les flux de diffusion. Dans ce travail, nous avons étudié un biofilm de Pseudomonas fluorescens et deux hydrogels modèles (agarose et alginate) pour lesquels l’autodiffusion (mouvement Brownien) et les coefficients de diffusion mutuels ont été quantifiés. La spectroscopie par corrélation de fluorescence a été utilisée pour mesurer les coefficients d'autodiffusion dans une volume confocal de ca. 1 m3 dans les gels ou les biofilms, tandis que les mesures de diffusion mutuelle ont été faites par cellule de diffusion. En outre, la voltamétrie sur microélectrode a été utilisée pour évaluer le potentiel de Donnan des gels afin de déterminer son impact sur la diffusion. Pour l'hydrogel d'agarose, les observations combinées d'une diminution du coefficient d’autodiffusion et de l’augmentation de la diffusion mutuelle pour une force ionique décroissante ont été attribuées au potentiel de Donnan du gel. Des mesures de l'effet Donnan (différence de -30 mV entre des forces ioniques de 10-4 et 10-1 M) et l'accumulation correspondante d’ions dans l'hydrogel (augmentation d’un facteur de 13 par rapport à la solution) ont indiqué que les interactions électrostatiques peuvent fortement influencer le flux de diffusion de cations...

Essential Role for the Major Autolysin in the Fibronectin-Binding Protein-Mediated Staphylococcus aureus Biofilm Phenotype▿

Houston, Patrick; Rowe, Sarah E.; Pozzi, Clarissa; Waters, Elaine M.; O'Gara, James P.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
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Staphylococcus aureus clinical isolates are capable of producing at least two distinct types of biofilm mediated by the fibronectin-binding proteins (FnBPs) or the icaADBC-encoded polysaccharide intercellular adhesin (PIA). Deletion of the major autolysin gene atl reduced primary attachment rates and impaired FnBP-dependent biofilm production on hydrophilic polystyrene in 12 clinical methicillin-resistant S. aureus (MRSA) isolates but had no effect on PIA-dependent biofilm production by 9 methicillin-susceptible S. aureus (MSSA) isolates. In contrast, Atl was required for both FnBP- and PIA-mediated biofilm development on hydrophobic polystyrene. Here we investigated the role of Atl in biofilm production on hydrophilic polystyrene. The alternative sigma factor σB, which represses RNAIII expression and extracellular protease production, was required for FnBP- but not PIA-dependent biofilm development. Furthermore, mutation of the agr locus enhanced FnBP-dependent biofilm development, whereas a sarA mutation, which increases protease production, blocked FnBP-mediated biofilm development. Mutation of sigB in MRSA isolate BH1CC lowered primary attachment rates, in part via reduced atl transcription. Posttranslational activation or inhibition of Atl activity with phenylmethylsulfonyl fluoride and polyanethole sodium sulfonate or mutation of the Atl amidase active site interfered with lytic activity and biofilm development. Consistent with these observations...