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The antibacterial effect of photodynamic therapy in dental plaque-derived biofilms

Fontana, C. R.; Abernethy, A. D.; Som, S.; Ruggiero, K.; Doucette, S.; Marcantonio, Rosemary Adriana Chierici; Boussios, C. I.; Kent, R.; Goodson, J. M.; Tanner, A. C. R.; Soukos, N. S.
Fonte: Wiley-Blackwell Publishing, Inc Publicador: Wiley-Blackwell Publishing, Inc
Tipo: Outros Formato: 751-759
ENG
Relevância na Pesquisa
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Background and Objective: Photodynamic therapy has been advocated as an alternative to antimicrobial agents to suppress subgingival species and to treat periodontitis. Bacteria located within dense biofilms, such as those encountered in dental plaque, have been found to be relatively resistant to antimicrobial therapy. In the present study, we investigated the ability of photodynamic therapy to reduce the number of bacteria in biofilms by comparing the photodynamic effects of methylene blue on human dental plaque microorganisms in the planktonic phase and in biofilms.Material and Methods: Dental plaque samples were obtained from 10 subjects with chronic periodontitis. Suspensions of plaque microorganisms from five subjects were sensitized with methylene blue (25 mu g/mL) for 5 min then exposed to red light. Multispecies microbial biofilms developed from the same plaque samples were also exposed to methylene blue (25 mu g/mL) and the same light conditions as their planktonic counterparts. In a second set of experiments, biofilms were developed with plaque bacteria from five subjects, sensitized with 25 or 50 mu g/mL of methylene blue and then exposed to red light. After photodynamic therapy...

Ação antibacteriana da cetramida associada às solucões irrigadoras sobre Enterococcus Faecalis

Nascimento, Camila Almeida
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 83 f. : il. color
POR
Relevância na Pesquisa
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Pós-graduação em Odontologia - FOAR; The aim of this study was to evaluate the action of conventional endodontic solutions such as sodium hypochlorite and chlorhexidine associated with cetrimide and QMiX, a commercial product composed by chlorhexidine, EDTA and cetrimide, on biofilm and planktonic phase of Enterococcus faecalis (ATCC 29212). The evaluated solutions were: G1: 2.5% Sodium Hypochlorite (NaOCl); G2: 2.5% NaOCl + 0.2% cetrimide (CTR); G3: 2% Chlorhexidine (CLX) 2%; G4: 2% CLX + 0.2% CTR; G5: 0.2% CTR; G6: QMiX. Saline solution was used as negative control. The study was divided into two chapters. In Chapter 1, the antibacterial activity of the solutions on microorganisms in planktonic phase and biofilm was evaluated. For direct contact with E. faecalis in planktonic phase, 50 μL of bacterial suspension were placed in tubes containing 1.45 mL of each irrigation solution or associations and after 1 and 3 minutes, neutralizing solutions were used to stop of the antimicrobial action of endodontic solutions. Decimal serial dilutions were performed and the suspensions were plated in Tryptic Soy agar medium (TSa). Dentin bovine blocks were used as substrate for induction of biofilms for 14 days. The biofilms were placed in contact with the solutions evaluated and transferred to test tubes containing neutralizing solution. After agitation for 60 seconds to suspend the remaining cells...

Susceptibility of staphylococcus epidermidis planktonic cells and biofilms to the lytic action of staphylococcus bacteriophage K

Cerca, Nuno; Oliveira, Rosário; Azeredo, Joana
Fonte: The Society for Applied Microbiology Publicador: The Society for Applied Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2007 ENG
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Aims: To evaluate differences in biofilm or planktonic bacteria susceptibility to be killed by the polyvalent antistaphylococcus bacteriophage K. Methods and Results: In this study, the ability of phage K to infect and kill several clinical isolates of Staphylococcus epidermidis was tested. Strains were grown in suspension or as biofilms to compare the susceptibility of both phenotypes to the phage lytic action. Most strains (10/11) were susceptible to phage K, and phage K was also effective in reducing biofilm biomass after 24 h of challenging. Biofilm cells were killed at a lower rate than the log-phase planktonic bacteria but at similar rate as stationary phase planktonic bacteria. Conclusions: Staphylococcus epidermidis biofilms and stationary growth phase planktonic bacteria are more resistant to phage K lysis than the exponential phase planktonic bacteria. Significance of study: This study shows the differences in Staph. epidermidis susceptibility to be killed by bacteriophage K, when grown in biofilm or planktonic phenotypes.; Fundação para a Ciência e a Tecnologia (FCT)

Morphogenesis control in Candida albicans and Candida dubliniensis through signaling molecules produced by planktonic and biofilm cells

Martins, Margarida; Henriques, Mariana; Azeredo, Joana; Rocha, Sílvia M.; Coimbra, Manuel A.; Oliveira, Rosário
Fonte: American Society for Microbiology. Publicador: American Society for Microbiology.
Tipo: Artigo de Revista Científica
Publicado em /12/2007 ENG
Relevância na Pesquisa
27.569822%
Morphogenesis control by chemical signaling molecules is beginning to be highlighted in Candida biology. The present study focuses on morphogenic compounds produced in situ by Candida albicans and Candida dubliniensis during planktonic and biofilm growth that may at least partially substantiate the effect promoted by supernatants in morphogenesis. For both species, planktonic versus biofilm supernatants were analyzed by headspace-solid-phase microextraction and gas chromatography-mass spectrometry. Both planktonic cells and biofilm supernatants of C. albicans and C. dubliniensis contained isoamyl alcohol, 2-phenylethanol, 1-dodecanol, E-nerolidol, and E,E-farnesol. Alcohol secretion profiles were species, culture mode, and growth time specific. The addition of exogenous alcohols to the cultures of both species inhibited the morphological transition from the yeast to the filamentous form by up to 50%. The physiological role of these alcohols was put to evidence by comparing the effects of a 96-h cultured supernatant with synthetic mixtures containing isoamyl alcohol, 2-phenylethanol, E-nerolidol, and E,E-farnesol at concentrations determined herein. All synthetic mixtures elicited a morphological effect similar to that observed for the corresponding supernatants when used to treat C. albicans and C. dubliniensis cultures...

Use of bacteriophages to control biofilms

Sillankorva, Sanna
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 19/02/2009 ENG
Relevância na Pesquisa
27.622173%
Tese de doutoramento em Engenharia Química e Biológica; After several years of abandonment, the use of bacteriophages (phages) for killing bacteria has withdrawn recent attention and reappraisal. This has led to a vast phage research, in varied fields, with impressive outcomes and currently several studies are ongoing with animals, horticulture and agriculture products, and even with humans. Despite this enthusiasm, there is a lack of research conserning phage utilization to reduce bacteria living on surfaces in a lifeform known as biofilms. This work explores the potential of phages in controlling bacteria present in single and dual species biofilms. Gram-negative Pseudomonas fluorescens and Gram-positive Staphylococcus lentus, widespread inhabitants of dairy plant surfaces and products were the studied bacterial hosts. P. fluorescens is the dominant microorganism present in the microflora of raw or pasteurized milk at the time of spoilage and commonly isolated from contaminated fresh meats and refrigerated products. S. lentus is coagulase-negative staphylococci (CoNS) and a member of the S. sciuri group. CoNS are the bacteria most frequently recovered from infected bovine and caprine mammary glands. Before performing biofilm studies...

Estudo das interações bacterianas do microbioma da pneumonia associada à ventilação sujeito a antibioterapia; Study of bacterial interactions in the microbiome of ventilator associated pneumonia subjected to antibiotherapy

Rodrigues, Tânia Alexandra Ferreira
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2014 POR
Relevância na Pesquisa
27.569822%
Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Engenharia Clínica); A ventilação assistida é um método de suporte à vida que surge na necessidade de assegurar a respiração pulmonar e/ou como forma medicamentosa. Mas tal como em qualquer outra prática clínica, a ventilação assistida não está isenta de riscos e complicações, surgindo frequentemente a pneumonia associada à ventilação (PAV). No que respeita ao tratamento da PAV bacteriana, atualmente os fármacos mais prescritos ainda são antibióticos, que contribuem também como importantes agentes profiláticos. Contudo, a emergência da resistência aos antibacterianos tem levantado sérios e preocupantes paradigmas no que respeita ao sucesso do tratamento da PAV. Por conseguinte, só recentemente a prevalência de biofilmes mistos e o seu envolvimento nas formas mais graves da infeção têm sido considerados, pelo que as certezas sobre a influência de diferentes espécies microbianas na evolução e resolução clínica da PAV são ainda muito escassas e insuficientemente compreendidas. Em virtude disso, é clara a necessidade de explorar de forma mais criteriosa a associação polimicrobiana e a resposta a fatores de stresse. Nesse sentido...

Feeding strategy assessment through fatty acid profiles in muscle of adults sea lamprey from the Western Iberian Coast

Lança, Maria João; Machado, Maria; Ferreira, Rui; Alves-Pereira, Isabel; Quintella, Bernardo Ruivo; Almeida, Pedro Raposo
Fonte: Scientia marina Publicador: Scientia marina
Tipo: Artigo de Revista Científica
ENG
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27.45453%
Fatty acid signature of sea lamprey Petromyzon marinus (L.) muscle were used as a tool to detect feeding strategies used during the species parasitic marine trophic phase. Adult sea lampreys were collected near the river mouth of six Portuguese river basins (i.e. Minho, Lima, Douro, Vouga, Mondego and Tagus) and muscle fatty acid profile characterized. The analysis on fatty acid composition of muscle neutral lipids showed the formation of two groups which pointed out that two feeding strategies may have been used by sea lampreys during the parasitic phase, based on the availability of ω-3 and ω-6 PUFA and on phytoplankton/zooplankton and bacterial detritus contribution in the sea lamprey host preferences. Two distinct lipid profiles were observed, probably related with two different trophic approaches, one typical of a top predator of a marine food web with a planktonic support, and the other much more diverse, including the same planktonic markers, together with biochemical clues that probably resulted from a parasitic phase that targeted directly fish consumers of detritus and benthic algae, and/or the predation of fish from a food web with a detritivorous base.

Resistance of oxidative stress in biofilm and planktonic cells

Jakubowski,Witold; Walkowiak,Bogdan
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 EN
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This work studied the susceptibility of biofilm produced by E. coli to oxidative stress, and compared the components of free radicals defences: level of glutathione, catalase and dismutase activities in planktonic and biofilm located cells. Results showed the diversity of responses to oxidative stress in bacterial cells in log or stationary phases in both planktonic and biofilm forms. The bacteria were exposed to free-radical donors (H2O2, tBOOH, menadione, SIN-1 or peroxynitrite) in a wide range of final concentrations, from 0.5 to 10mM. Different level of toxicity of individual donors, independence of cell type (planktonic forms or biofilm) and phases of growth were observed. The highest oxidative stress resistance was observed for the cells in logarithmic phase of growth treated with H2O2, both in planktonic and biofilm forms, whereas for the cells in stationary phase, the highest resistance was observed for menadione. These results showed higher efficiency of agents based on superoxide anion donors in combating bacteria colonizing abiotic surfaces stainless steel (AISI 316L).

Biofilms and Planktonic Cells of Pseudomonas aeruginosa Have Similar Resistance to Killing by Antimicrobials

Spoering, Amy L.; Lewis, Kim
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2001 EN
Relevância na Pesquisa
28.125286%
Biofilms are considered to be highly resistant to antimicrobial agents. Strictly speaking, this is not the case—biofilms do not grow in the presence of antimicrobials any better than do planktonic cells. Biofilms are indeed highly resistant to killing by bactericidal antimicrobials, compared to logarithmic-phase planktonic cells, and therefore exhibit tolerance. It is assumed that biofilms are also significantly more tolerant than stationary-phase planktonic cells. A detailed comparative examination of tolerance of biofilms versus stationary- and logarithmic-phase planktonic cells with four different antimicrobial agents was performed in this study. Carbenicillin appeared to be completely ineffective against both stationary-phase cells and biofilms. Killing by this β-lactam antibiotic depends on rapid growth, and this result confirms the notion of slow-growing biofilms resembling the stationary state. Ofloxacin is a fluoroquinolone antibiotic that kills nongrowing cells, and biofilms and stationary-phase cells were comparably tolerant to this antibiotic. The majority of cells in both populations were eradicated at low levels of ofloxacin, leaving a fraction of essentially invulnerable persisters. The bulk of the population in both biofilm and stationary-phase cultures was tolerant to tobramycin. At very high tobramycin concentrations...

Role of Fusobacterium nucleatum and Coaggregation in Anaerobe Survival in Planktonic and Biofilm Oral Microbial Communities during Aeration

Bradshaw, David J.; Marsh, Philip D.; Watson, G. Keith; Allison, Clive
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/1998 EN
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Coaggregation is a well-characterized phenomenon by which specific pairs of oral bacteria interact physically. The aim of this study was to examine the patterns of coaggregation between obligately anaerobic and oxygen-tolerant species that coexist in a model oral microbial community. Obligate anaerobes other than Fusobacterium nucleatum coaggregated only poorly with oxygen-tolerant species. In contrast, F. nucleatum was able to coaggregate not only with both oxygen-tolerant and other obligately anaerobic species but also with otherwise-noncoaggregating obligate anaerobe–oxygen-tolerant species pairs. The effects of the presence or absence of F. nucleatum on anaerobe survival in both the biofilm and planktonic phases of a complex community of oral bacteria grown in an aerated (gas phase, 200 ml of 5% CO2 in air · min−1) chemostat system were then investigated. In the presence of F. nucleatum, anaerobes persisted in high numbers (>107 · ml−1 in the planktonic phase and >107 · cm−2 in 4-day biofilms). In an equivalent culture in the absence of F. nucleatum, the numbers of black-pigmented anaerobes (Porphyromonas gingivalis and Prevotella nigrescens) were significantly reduced (P ≤ 0.001) in both the planktonic phase and in 4-day biofilms...

Role of Nutrient Limitation and Stationary-Phase Existence in Klebsiella pneumoniae Biofilm Resistance to Ampicillin and Ciprofloxacin

Anderl, Jeff N.; Zahller, Jeff; Roe, Frank; Stewart, Philip S.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2003 EN
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Biofilms formed by Klebsiella pneumoniae resisted killing during prolonged exposure to ampicillin or ciprofloxacin even though these agents have been shown to penetrate bacterial aggregates. Bacteria dispersed from biofilms into medium quickly regained most of their susceptibility. Experiments with free-floating bacteria showed that stationary-phase bacteria were protected from killing by either antibiotic, especially when the test was performed in medium lacking carbon and nitrogen sources. These results suggested that the antibiotic tolerance of biofilm bacteria could be explained by nutrient limitation in the biofilm leading to stationary-phase existence of at least some of the cells in the biofilm. This mechanism was supported by experimental characterization of nutrient availability and growth status in biofilms. The average specific growth rate of bacteria in biofilms was only 0.032 h−1 compared to the specific growth rate of planktonic bacteria of 0.59 h−1 measured in the same medium. Glucose did not penetrate all the way through the biofilm, and oxygen was shown to penetrate only into the upper 100 μm. The specific catalase activity was elevated in biofilm bacteria to a level similar to that of stationary-phase planktonic cells. Transmission electron microscopy revealed that bacteria were affected by ampicillin near the periphery of the biofilm but were not affected in the interior. Taken together...

Heavy Metal Resistance of Biofilm and Planktonic Pseudomonas aeruginosa

Teitzel, Gail M.; Parsek, Matthew R.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /04/2003 EN
Relevância na Pesquisa
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A study was undertaken to examine the effects of the heavy metals copper, lead, and zinc on biofilm and planktonic Pseudomonas aeruginosa. A rotating-disk biofilm reactor was used to generate biofilm and free-swimming cultures to test their relative levels of resistance to heavy metals. It was determined that biofilms were anywhere from 2 to 600 times more resistant to heavy metal stress than free-swimming cells. When planktonic cells at different stages of growth were examined, it was found that logarithmically growing cells were more resistant to copper and lead stress than stationary-phase cells. However, biofilms were observed to be more resistant to heavy metals than either stationary-phase or logarithmically growing planktonic cells. Microscopy was used to evaluate the effect of copper stress on a mature P. aeruginosa biofilm. The exterior of the biofilm was preferentially killed after exposure to elevated concentrations of copper, and the majority of living cells were near the substratum. A potential explanation for this is that the extracellular polymeric substances that encase a biofilm may be responsible for protecting cells from heavy metal stress by binding the heavy metals and retarding their diffusion within the biofilm.

Transcriptome Analysis of Pseudomonas aeruginosa Growth: Comparison of Gene Expression in Planktonic Cultures and Developing and Mature Biofilms†

Waite, Richard D.; Papakonstantinopoulou, Anastasia; Littler, Eddie; Curtis, Michael A.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2005 EN
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The transcriptomes of logarithmic- and stationary-phase Pseudomonas aeruginosa planktonic cultures and static biofilms of different stages of development were compared. Developing and confluent biofilm transcriptomes were found to be related to those of logarithmic- and stationary-phase planktonic cultures, respectively. In addition, a number of novel genes were up-regulated in developing and confluent biofilms, including genes encoding putative solute transport proteins and transcriptional regulators, respectively.

Interrelationships between Colonies, Biofilms, and Planktonic Cells of Pseudomonas aeruginosa▿ †

Mikkelsen, H.; Duck, Z.; Lilley, K. S.; Welch, M.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /03/2007 EN
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Pseudomonas aeruginosa is a gram-negative bacterium and an opportunistic human pathogen that causes chronic infections in immunocompromised individuals. These infections are hard to treat, partly due to the high intrinsic resistance of the bacterium to clinically used antibiotics and partly due to the formation of antibiotic-tolerant biofilms. The three most common ways of growing bacteria in vitro are as planktonic cultures, colonies on agar plates, and biofilms in continuous-flow systems. Biofilms are known to express genes different from those of planktonic cells, and biofilm cells are generally believed to closely resemble planktonic cells in stationary phase. However, few, if any, studies have examined global gene expression in colonies. We used a proteomic approach to investigate the interrelationships between planktonic cells, colonies, and biofilms under comparable conditions. Our results show that protein profiles in colonies resemble those of planktonic cells. Furthermore, contrary to what has been reported previously, the protein profiles of biofilms were found to more closely resemble those of exponentially growing planktonic cells than those of planktonic cells in the stationary phase. These findings raise some intriguing questions about the true nature of biofilms.

Morphogenesis Control in Candida albicans and Candida dubliniensis through Signaling Molecules Produced by Planktonic and Biofilm Cells▿

Martins, Margarida; Henriques, Mariana; Azeredo, Joana; Rocha, Sílvia M.; Coimbra, Manuel A.; Oliveira, Rosário
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.569822%
Morphogenesis control by chemical signaling molecules is beginning to be highlighted in Candida biology. The present study focuses on morphogenic compounds produced in situ by Candida albicans and Candida dubliniensis during planktonic and biofilm growth that may at least partially substantiate the effect promoted by supernatants in morphogenesis. For both species, planktonic versus biofilm supernatants were analyzed by headspace-solid-phase microextraction and gas chromatography-mass spectrometry. Both planktonic cells and biofilm supernatants of C. albicans and C. dubliniensis contained isoamyl alcohol, 2-phenylethanol, 1-dodecanol, E-nerolidol, and E,E-farnesol. Alcohol secretion profiles were species, culture mode, and growth time specific. The addition of exogenous alcohols to the cultures of both species inhibited the morphological transition from the yeast to the filamentous form by up to 50%. The physiological role of these alcohols was put to evidence by comparing the effects of a 96-h cultured supernatant with synthetic mixtures containing isoamyl alcohol, 2-phenylethanol, E-nerolidol, and E,E-farnesol at concentrations determined herein. All synthetic mixtures elicited a morphological effect similar to that observed for the corresponding supernatants when used to treat C. albicans and C. dubliniensis cultures...

Comparison of Planktonic and Biofilm Cultures of Pseudomonas fluorescens DSM 8341 Cells Grown on Fluoroacetate▿

Heffernan, Barry; Murphy, Cormac D.; Casey, Eoin
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.569822%
Comparisons between the physiological properties of Pseudomonas fluorescens biofilm cells grown in a tubular biofilm reactor and planktonic cells grown in a chemostat were performed. Fluoroacetate was the sole carbon source for all experiments. The performance of cells was assessed using cell cycle kinetics and by determining specific fluoroacetate utilization rates. Cell cycle kinetics were studied by flow cytometry in conjunction with the fluorescent stain propidium iodide. Determination of the DNA content of planktonic and biofilm cultures showed little difference between the two modes of growth. Cultures with comparable specific glycolate utilization rates had similar percentages of cells in the B phase of the cell cycle, indicating similar growth rates. Specific fluoroacetate utilization rates showed the performance of planktonic cells to be superior to that of biofilm cells, with more fluoroacetate utilized per cell at similar specific fluoroacetate loading rates. A consequence of this decreased biofilm performance was the accumulation of glycolate in the effluent of biofilm cultures. This accumulation of glycolate was not observed in the effluent of planktonic cultures. Spatial stratification of oxygen within the biofilm was identified as a possible explanation for the overflow metabolism of glycolate and the decreased performance of the biofilm cells.

Lipidomics of Candida albicans biofilms reveals phase-dependent production of phospholipid molecular classes and role for lipid rafts in biofilm formation

Lattif, Ali Abdul; Mukherjee, Pranab K.; Chandra, Jyotsna; Roth, Mary R.; Welti, Ruth; Rouabhia, Mahmoud; Ghannoum, Mahmoud A.
Fonte: Society for General Microbiology Publicador: Society for General Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2011 EN
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27.759065%
Candida albicans-associated bloodstream infections are linked to the ability of this yeast to form biofilms. In this study, we used lipidomics to compare the lipid profiles of C. albicans biofilms and planktonic cells, in early and mature developmental phases. Our results showed that significant differences exist in lipid composition in both developmental phases. Biofilms contained higher levels of phospholipid and sphingolipids than planktonic cells (nmol per g biomass, P<0.05 for all comparisons). In the early phase, levels of lipid in most classes were significantly higher in biofilms compared to planktonic cells (P≤0.05). The ratio of phosphatidylcholine to phosphatidylethanolamine was lower in biofilms compared to planktonic cells in both early (1.17 vs 2.52, P≤0.001) and late (2.34 vs 3.81, P≤0.001) developmental phases. The unsaturation index of phospholipids decreased with time, with this effect being particularly strong for biofilms. Inhibition of the biosynthetic pathway for sphingolipid [mannosyl diinositolphosphoryl ceramide, M(IP)2C] by myriocin or aureobasidin A, and disruption of the gene encoding inositolphosphotransferase (Ipt1p), abrogated the ability of C. albicans to form biofilms. The differences in lipid profiles between biofilms and planktonic Candida cells may have important implications for the biology and antifungal resistance of biofilms.

Planktonic Aggregates of Staphylococcus aureus Protect against Common Antibiotics

Haaber, Jakob; Cohn, Marianne Thorup; Frees, Dorte; Andersen, Thorbjørn Joest; Ingmer, Hanne
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 18/07/2012 EN
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27.523047%
Bacterial cells are mostly studied during planktonic growth although in their natural habitats they are often found in communities such as biofilms with dramatically different physiological properties. We have examined another type of community namely cellular aggregates observed in strains of the human pathogen Staphylococcus aureus. By laser-diffraction particle–size analysis (LDA) we show, for strains forming visible aggregates, that the aggregation starts already in the early exponential growth phase and proceeds until post-exponential phase where more than 90% of the population is part of the aggregate community. Similar to some types of biofilm, the structural component of S. aureus aggregates is the polysaccharide intercellular adhesin (PIA). Importantly, PIA production correlates with the level of aggregation whether altered through mutations or exposure to sub-inhibitory concentrations of selected antibiotics. While some properties of aggregates resemble those of biofilms including increased mutation frequency and survival during antibiotic treatment, aggregated cells displayed higher metabolic activity than planktonic cells or cells in biofilm. Thus, our data indicate that the properties of cells in aggregates differ in some aspects from those in biofilms. It is generally accepted that the biofilm life style protects pathogens against antibiotics and the hostile environment of the host. We speculate that in aggregate communities S. aureus increases its tolerance to hazardous environments and that the combination of a biofilm-like environment with mobility has substantial practical and clinical importance.

Whole Transcriptome Analysis of Acinetobacter baumannii Assessed by RNA-Sequencing Reveals Different mRNA Expression Profiles in Biofilm Compared to Planktonic Cells

Rumbo-Feal, Soraya; Gómez, Manuel J.; Gayoso, Carmen; Álvarez-Fraga, Laura; Cabral, María P.; Aransay, Ana M.; Rodríguez-Ezpeleta, Naiara; Fullaondo, Ane; Valle, Jaione; Tomás, María; Bou, Germán; Poza, Margarita
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 30/08/2013 EN
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Acinetobacterbaumannii has emerged as a dangerous opportunistic pathogen, with many strains able to form biofilms and thus cause persistent infections. The aim of the present study was to use high-throughput sequencing techniques to establish complete transcriptome profiles of planktonic (free-living) and sessile (biofilm) forms of A. baumannii ATCC 17978 and thereby identify differences in their gene expression patterns. Collections of mRNA from planktonic (both exponential and stationary phase cultures) and sessile (biofilm) cells were sequenced. Six mRNA libraries were prepared following the mRNA-Seq protocols from Illumina. Reads were obtained in a HiScanSQ platform and mapped against the complete genome to describe the complete mRNA transcriptomes of planktonic and sessile cells. The results showed that the gene expression pattern of A. baumannii biofilm cells was distinct from that of planktonic cells, including 1621 genes over-expressed in biofilms relative to stationary phase cells and 55 genes expressed only in biofilms. These differences suggested important changes in amino acid and fatty acid metabolism, motility, active transport, DNA-methylation, iron acquisition, transcriptional regulation, and quorum sensing, among other processes. Disruption or deletion of five of these genes caused a significant decrease in biofilm formation ability in the corresponding mutant strains. Among the genes over-expressed in biofilm cells were those in an operon involved in quorum sensing. One of them...

The importance of the pelagic larval phase of the wedge shell Donax trunculus (L.)

Pereira, Alexandre Miguel Moura
Fonte: Universidade do Algarve Publicador: Universidade do Algarve
Tipo: Tese de Doutorado
Publicado em //2013 ENG
Relevância na Pesquisa
36.957026%
The wedge shell, Donax trunculus, inhabits high energy environment of exposed sandy beaches from the Atlantic coast of France to Senegal. Like all Donacidae, it is relative small, flat-shaped with elongated solid shells. It is a highly demanded and valuable species mainly in Algarve, with the dredge fleet increasing the pressure on species stocks. In 1986 the Portuguese Institute for the Ocean and Atmosphere (IPMA) initiated a bivalve survey program to evaluate the stock status of species with economical valuable but always on the adult population. Since then, several managing measures were implemented to guarantee bivalves’ sustainable exploitation. Despite the available information on the abundance and distribution of the wedge shell along the Algarve coast, no information on the larval planktonic phase is available. To fill in this gap, the present study aimed at obtaining, for the first time information on the broodstock condition and on the pelagic phase of the wedge shell in the Algarve coast.; A conquilha, Donax trunculus, habita em sedimentos arenosos de praias com algum hidrodinamismo desde a costa atlântica de França até ao Senegal. Tal como outros Donacidae, é relativamente pequena, achatada com uma concha sólida e alongada. É uma espécie com elevado valor económico e muito procurada especialmente no Algarve...