Biofilm dispersal and exacerbations of cystic fibrosis lung disease.
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
S Kjelleberg
Publications and source records attributed to S Kjelleberg.
Furanones.
The red alga Delisea pulchra has been a model organism for understanding the ecological role of secondary metabolites as natural antifoulants. Furanones are produced by the plant and delivered to the surface at a concentration where they regulate bacterial colonisation and the settlement of epibiota. This biological understanding has led to the application of furanones as inhibitors of bacterial- and macro-fouling. Furanones inhibit bacterial colonisation and biofilm development through interference with a key bacterial quorum-sensing pathway, the acylated homoserine lactone regulatory system in Gram-negative bacteria. They also interfere with the alternative AI-2 signalling system in Gram-negative and Gram-positive bacteria. Synthetic programs have developed a library of more than 200 furanone and furanone-analogues including surface attached-furanones. These furanone analogues are potent anti-infectives and inhibit pathogenic phenotypes in Gram-negative and Gram-positive bacteria as demonstrated in-vitro using gene microarrays, and in-vivo using mouse models. Additionally, furanones inhibit the expression of bacterial exo-enzymes that actively degrade components of the immune system thereby enhancing the immune response. Surface-attached furanones immobilised on catheters also inhibit bacterial attachment and retain activity for extended periods. Furanones are strong deterrents of the settlement and growth of macrofouling organisms and as such have potential application as a marine antifouling technology. Laboratory antifouling assays have been used to identify effective and safe furanone-analogues while field trials of furanones incorporated into coatings and polymers demonstrate efficacies similar to commercial biocides. Further development is required to control the release of compounds from suitable carriers to extend coating/polymer lifespans. This review summarises the extensive work on furanones focusing on their natural and applied antifouling activities.
Anti-Infective Agents↗
Inhibition of fungal colonization by Pseudoalteromonas tunicata provides a competitive advantage during surface colonization.
The marine epiphytic bacterium Pseudoalteromonas tunicata produces a range of extracellular secondary metabolites that inhibit an array of common fouling organisms, including fungi. In this study, we test the hypothesis that the ability to inhibit fungi provides P. tunicata with an advantage during colonization of a surface. Studies on a transposon-generated antifungal-deficient mutant of P. tunicata, FM3, indicated that a long-chain fatty acid-coenzyme A ligase is involved in the production of a broad-range antifungal compound by P. tunicata. Flow cell experiments demonstrated that production of an antifungal compound provided P. tunicata with a competitive advantage against a marine yeast isolate during surface colonization. This compound enabled P. tunicata to disrupt an already established fungal biofilm by decreasing the number of yeast cells attached to the surface by 66% +/- 9%. For in vivo experiments, the wild-type and FM3 strains of P. tunicata were used to inoculate the surface of the green alga Ulva australis. Double-gradient denaturing gradient gel electrophoresis analysis revealed that after 48 h, the wild-type P. tunicata had outcompeted the surface-associated fungal community, whereas the antifungal-deficient mutant had no effect on the fungal community. Our data suggest that P. tunicata is an effective competitor against fungal surface communities in the marine environment.
Antifungal Agents↗
The LuxR receptor: the sites of interaction with quorum-sensing signals and inhibitors.
The function of LuxR homologues as quorum sensors is mediated by the binding of N-acyl-L-homoserine lactone (AHL) signal molecules to the N-terminal receptor site of the proteins. In this study, site-directed mutagenesis was carried out of the amino acid residues comprising the receptor site of LuxR from Vibrio fischeri, and the ability of the L42A, L42S, Y62F, W66F, D79N, W94D, V109D, V109T and M135A LuxR mutant proteins to activate green fluorescent protein expression from a P(luxI) promoter was measured. X-ray crystallographic studies of the LuxR homologue TraR indicated that residues Y53 and W57 form hydrogen bonds to the 1-carbonyl group and the ring carbonyl group, respectively, of the cognate AHL signal. Based on the activity and signal specificity of the LuxR mutant proteins, and on molecular modelling, a model is suggested in which Y62 (corresponding to Y53 in TraR) forms a hydrogen bond with the ring carbonyl group rather than the 1-carbonyl group, while W66 (corresponding to W57 in TraR) forms a hydrogen bond to the 1-carbonyl group. This flips the position of the acyl side chain in the LuxR/signal molecule complex compared to the TraR/signal molecule complex. Halogenated furanones from the marine alga Delisea pulchra and the synthetic signal analogue N-(sulfanylacetyl)-L-homoserine lactone can block quorum sensing. The LuxR mutant proteins were insensitive to inhibition by N-(propylsulfanylacetyl)-L-homoserine lactone. In contrast, the mutations had only a minor effect on the sensitivity of the proteins to halogenated furanones, and the data strongly suggest that these compounds do not compete in a 'classic' way with N-3-oxohexanoyl-L-homoserine lactone for the binding site. Based on modelling and experimental data it is suggested that these compounds bind in a non-agonist fashion.
4-Butyrolactone↗
Clinical significance of seeding dispersal in biofilms.
Explore the source record for details and available documents.
Biofilms↗
Biofilm formation and sloughing in Serratia marcescens are controlled by quorum sensing and nutrient cues.
We describe here a role for quorum sensing in the detachment, or sloughing, of Serratia marcescens filamentous biofilms, and we show that nutrient conditions affect the biofilm morphotype. Under reduced carbon or nitrogen conditions, S. marcescens formed a classical biofilm consisting of microcolonies. The filamentous biofilm could be converted to a microcolony-type biofilm by switching the medium after establishment of the biofilm. Similarly, when initially grown as a microcolony biofilm, S. marcescens could be converted back to a filamentous biofilm by increasing the nutrient composition. Under high-nutrient conditions, an N-acyl homoserine lactone quorum-sensing mutant formed biofilms that were indistinguishable from the wild-type biofilms. Similarly, other quorum-sensing-dependent behaviors, such as swarming motility, could be rendered quorum sensing independent by manipulating the growth medium. Quorum sensing was also found to be involved in the sloughing of the filamentous biofilm. The biofilm formed by the bacterium consistently sloughed from the substratum after approximately 75 to 80 h of development. The quorum-sensing mutant, when supplemented with exogenous signal, formed a wild-type filamentous biofilm and sloughed at the same time as the wild type, and this was independent of surfactant production. When we removed the signal from the quorum-sensing mutant prior to the time of sloughing, the biofilm did not undergo significant detachment. Together, the data suggest that biofilm formation by S. marcescens is a dynamic process that is controlled by both nutrient cues and the quorum-sensing system.
Biofilms↗
The control of Staphylococcus epidermidis biofilm formation and in vivo infection rates by covalently bound furanones.
In order to overcome the continuing infection rate associated with biomaterials, the use of covalently bound furanones as an antibiofilm coating for biomaterials has been investigated. Furanones have previously been shown to inhibit growth of Gram-positive and Gram-negative bacteria. The aim of these studies were to covalently bind furanones to polymers and to test their efficacy for inhibiting biofilm formation of Staphylococcus epidermidis and in vivo infection rate. Two methods of covalent attachment of furanones were used. The first, a co-polymerisation with a styrene polymer, and second, a plasma-1-ethyl-3-(dimethylaminopropyl) carbodiimide (EDC) reaction to produce furanone-coated catheters. Biofilm formation by S. epidermidis in vitro was inhibited by 89% for polystryene-furanone disks and by 78% by furanone-coated catheters (p<0.01). In an in vivo sheep model we found furanones were effective at controlling infection for up to 65 days. Furanones have potential to be used as a coating for biomaterials to control infection caused by S. epidermidis.
Animals↗
Influence of petroleum contamination and biostimulation treatment on the diversity of Pseudomonas spp. in soil microcosms as evaluated by 16S rRNA based-PCR and DGGE.
AIMS: The aim of this study was to apply a group specific PCR system followed by denaturing gradient gel electrophoresis (DGGE) analysis to evaluate the effect of oil contamination and the biostimulation process on the diversity of Pseudomonas populations in soil ecosystems. METHODS AND RESULTS: Direct DNA extraction from biostimulated- and oil-contaminated soil samples was performed. Primers specific for the genus Pseudomonas spp. were used to amplify 16S rRNA genes and then a semi-nested PCR reaction was applied to obtain smaller fragments for comparing the PCR products by DGGE. Whether in bulk, oil-contaminated or biostimulated soils, the DGGE profiles revealed little change in Pseudomonas community throughout the 270 days of experiment. The presence of a few additional bands observed only in treated samples indicated that a bacterial shift occurred with the addition of nutrients and with oil contamination. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of semi-nested PCR and DGGE was found to be a rapid and sensitive technique to study the diversity within the genus Pseudomonas and may be suitable for further studies concerning the role of this bacterial group in large-scale oil-contaminated areas.
Ammonium Sulfate↗
Defences against oxidative stress during starvation in bacteria.
It now seems clear that starvation adaptation is important for cells to initiate long-term survival under conditions of not only nutrient depletion but to develop resistance to other stresses, most notably oxidative stress. Clearly, oxidative stress is a condition likely to be perceived by many bacteria, for example, in the form of reactive oxygen species derived from metabolic processes or from near-UV exposure. We have found evidence for a large degree of overlap in the cell's use of global regulators to deal with both starvation and oxidative stress. Both SpoT and AI-2 signalling pathways are important regulators of starvation and stress adaptation as well as the alternative sigma factor, RpoE. We also present evidence that suggests that AI-2 signalling can mediate starvation adaptation at the molecular level by increasing the stability of the mRNAs so that cells are prepared for rapid response to nutrient addition. Moreover, such extracellular signals mediate intraspecies communication to enable enhanced survival and stress resistance of neighbouring bacterial cells. It is likely that bacteria rely on a suite of effects between cells and on transcription, translation and post-translationalprocesses, mediated by global regulators and signalling molecules, to meet their needs for growth and survival.
Bacterial Proteins↗
Halogenated furanones from the red alga, Delisea pulchra, inhibit carbapenem antibiotic synthesis and exoenzyme virulence factor production in the phytopathogen Erwinia carotovora.
The plant pathogen Erwinia carotovora regulates expression of virulence factors and antibiotic production via an N-3-oxohexanoyl-L-homoserine lactone (3-oxo-C6-HSL) dependent quorum sensing mechanism. The marine alga Delisea pulchra produces halogenated furanones known to antagonise 3-oxo-C6-HSL activity. We have tested the effects of a halogenated furanone on the production of carbapenem, cellulase and protease in E. carotovora. Despite differences in the regulatory mechanisms controlling carbapenem and exoenzyme production each was inhibited by the algal metabolite. We present evidence to suggest that the furanone dependent inhibition of carbapenem production is a result of the disruption of the 3-oxo-C6-HSL dependent expression of the carABCDEFGH operon.
4-Butyrolactone↗
Kinetics of the AHL regulatory system in a model biofilm system: how many bacteria constitute a "quorum"?
Acylated homoserine lactones (AHLs) regulate a wide variety of phenotypes in Gram-negative bacteria. Most research suggests that AHL-mediated phenotypes are not expressed in populations until late logarithmic phase or stationary phase. Here, we model how the concentration of AHLs inside bacterial cells and in a biofilm changes over time as a function of population growth rate, diffusion of AHLs and the rate of autoinduction. Our theoretical results show that the concentration of AHLs inside a single bacterium (and by implication induction of a phenotype) has a non-trivial behaviour over time, and often exhibits a rapid increase early in population growth. This rapid increase is followed by a plateau, followed by another rise in the concentration of AHLs, to a second plateau. High concentrations of AHLs inside the bacterial cell early in population growth are positively affected by slow diffusion rates out of the cell and the biofilm, slow bacterial growth rates and fast autoinduction. In contrast, fast growth rates, slow autoinduction rates and high diffusion rates result in a high concentration plateau in stationary phase. More generally, the density-dependent nature of AHL regulation can be viewed as a trade-off between factors that dilute intracellular concentrations of AHLs (diffusion out of the cell, cell division), and those that increase concentrations (a slowing or restriction of diffusion or growth, or autoinduction). These results suggest that expression of AHL-mediated phenotypes can occur at relatively low cell densities and low external/environmental AHL concentrations.
4-Butyrolactone↗
Genetic and chemical tools for investigating signaling processes in biofilms.
Explore the source record for details and available documents.
4-Butyrolactone↗
A new metabolite from the marine bacterium Vibrio angustum S14.
The new metabolite [1-(2'-methylpropoxy)-2-hydroxy-2-methylpropoxy]butane was isolated from the cell-free culture supernatant of the marine bacterium Vibrio angustum S14 as part of studies investigating the role of chemical signals in prokaryote--prokaryote and prokaryote--eukaryote interactions. The structure was elucidated by interpretation of its high-field NMR and mass spectrometric data. [1-(2'-Methylpropoxy)-2-hydroxy-2-methylpropoxy]butane induced the acylated homoserine lactone (AHL) reporter system in Agrobacterium tumefaciens and bioluminescence in Vibrio harveyi.
Butanes↗
Pseudoalteromonas ulvae sp. nov., a bacterium with antifouling activities isolated from the surface of a marine alga.
A dark-purple marine bacterium that inhibits the germination of marine algal spores and the settlement of invertebrate larvae has been characterized and assessed for taxonomic assignment. Two strains, designated UL12T and UL13, were isolated from the surface of the common marine alga Ulva lactuca. Based on 16S rDNA sequencing, UL12T and UL13 were found to show the highest similarity (97%) to members of the genus Pseudoalteromonas. DNA-DNA hybridization studies demonstrated less than 28% genomic DNA relatedness between these isolates and closely related Pseudoalteromonas species and greater than 65% homology between UL12T and UL13. The two isolates were found to display identical characteristics and are strict aerobes, motile by means of single polar flagella, exhibit non-fermentative metabolism and require sodium ions for growth. The isolates hydrolyse gelatin and can utilize citrate, maltose, mannose and glucose but not trehalose, sucrose, fructose, lactose or glycerol as sole carbon sources. The molecular evidence together with the phenotypic characteristics show that this bacterium constitutes a new species within the genus Pseudoalteromonas. The name Pseudoalteromonas ulvae sp. nov. is proposed for this bacterium and the type strain is UL12T (= UNSW 095600T = NCIMB 13762T).
Animals↗
Inhibition of algal spore germination by the marine bacterium Pseudoalteromonas tunicata.
A collection of 56 bacteria isolated from different surfaces in the marine environment were assayed for their effects on the germination of spores from the common green alga Ulva lactuca. Thirteen bacterial isolates were shown to inhibit spore germination. Of these bacteria, Pseudoalteromonas tunicata displayed the most pronounced effects against algal spores. Further characterisation of the anti-algal activity of P. tunicata was performed and it was found that this bacterium produces an extracellular component with specific activity toward algal spores that is heat-sensitive, polar and between 3 and 10 kDa in size. This biologically active compound was also found to prevent the germination of spores from the red alga Polysiphonia sp. and, given the widespread occurrence of P. tunicata in a range of marine habitats, this may suggest that it is effective against a variety of marine algae.
Journal Article↗
SmcR-dependent regulation of adaptive phenotypes in Vibrio vulnificus.
Vibrio vulnificus contains homologues of the V. harveyi luxR and luxS genes. A null mutation in smcR (luxR) resulted in a defect in starvation survival, inhibition of starvation-induced maintenance of culturability that occurs when V. vulnificus is starved prior to low-temperature incubation, and increased expression of stationary-phase phenotypes.
Adaptation, Biological↗
The marine pathogen Vibrio vulnificus encodes a putative homologue of the Vibrio harveyi regulatory gene, luxR: a genetic and phylogenetic comparison.
Vibrio vulnificus is an opportunistic pathogen that exhibits numerous virulence factors, including the secretion of a zinc metalloprotease and the production of a capsule. We have cloned and sequenced a gene from V. vulnificus that is a homologue of the positive transcriptional regulator, luxR, of the lux operon in Vibrio harveyi. This gene encodes a putative, single complete open reading frame designated smcR, which shares greater than 75% nucleotide identity with luxR of V. harveyi. The deduced amino acid sequence of the putative SmcR protein is more than 90% identical and 95% similar to that of LuxR of V. harveyi, suggesting that V. vulnificus possesses a member of the family of signal-response genes recently described in Vibrio cholerae and in Vibrio parahaemolyticus. Our data also demonstrate that, in addition to V. vulnificus, all six Vibrio spp. tested contained genes that hybridized with the luxR probe. We also present evidence that this regulatory protein was inherited from a common ancestor, and that the gene is ancient and widespread in marine Vibrio spp.
Amino Acid Sequence↗
Luminescence control in the marine bacterium Vibrio fischeri: An analysis of the dynamics of lux regulation.
A mathematical model has been developed based on the fundamental properties of the control system formed by the lux genes and their products in Vibrio fischeri. The model clearly demonstrates how the components of this system work together to create two, stable metabolic states corresponding to the expression of the luminescent and non-luminescent phenotypes. It is demonstrated how the cell can "switch" between these steady states due to changes in parameters describing metabolic processes and the extracellular concentration of the signal molecule N-3-oxohexanoyl-l-homoserine lactone. In addition, it is shown how these parameters influence how sensitive the switch mechanism is to cellular LuxR and N-3-oxohexanoyl-l-homoserine lactone and complex concentration. While these properties could lead to the collective phenomenon known as quorum sensing, the model also predicts that under certain metabolic circumstances, basal expression of the lux genes could cause a cell to luminesce in the absence of extracellular signal molecule. Finally, the model developed in this study provides a basis for analysing the impact of other levels of control upon lux regulation.
4-Butyrolactone↗