Showing papers on "Biofilm matrix published in 2001"

Biofilm penetration and disinfection efficacy of alkaline hypochlorite and chlorosulfamates

Abstract: Aims: The purpose of this study was to compare the efficacy, in terms of bacterial biofilm penetration and killing, of alkaline hypochlorite (pH 11) and chlorosulfamate (pH 5·5) formulations. Methods and Results: Two species biofilms of Pseudomonas aeruginosa and Klebsiella pneumoniae were grown by flowing a dilute medium over inclined stainless steel slides for 6 d. Microelectrode technology was used to measure concentration profiles of active chlorine species within the biofilms in response to treatment at a concentration of 1000 mg total chlorine l–1. Chlorosulfamate formulations penetrated biofilms faster than did hypochlorite. The mean penetration time into ~1 mm-thick biofilms for chlorosulfamate (6 min) was only one-eighth as long as for the same concentration of hypochlorite (48 min). Chloride ion penetrated biofilms rapidly (5 min) with an effective diffusion coefficient in the biofilm that was close to the value for chloride in water. Biofilm bacteria were highly resistant to killing by both antimicrobial agents. Biofilms challenged with 1000 mg l–1 alkaline hypochlorite or chlorosulfamate for 1 h experienced 0·85 and 1·3 log reductions in viable cell numbers, respectively. Similar treatment reduced viable numbers of planktonic bacteria to non-detectable levels (log reduction greater than 6) within 60 s. Aged planktonic and resuspended laboratory biofilm bacteria were just as susceptible to hypochlorite as fresh planktonic cells. Conclusions: Chlorosulfamate transport into biofilm was not retarded whereas hypochlorite transport clearly was retarded. Superior penetration by chlorosulfamate was hypothesized to be due to its lower capacity for reaction with constituents of the biofilm. Poor biofilm killing despite direct measurement of effective physical penetration of the antimicrobial agent into the biofilm demonstrates that bacteria in the biofilm are protected by some mechanism other than simple physical shielding by the biofilm matrix. Significance and Impact of the Study: This study lends support to the theory that the penetration of antimicrobial agents into microbial biofilms is controlled by the reactivity of the antimicrobial agent with biofilm components. The finding that chlorine-based biocides can penetrate, but fail to kill, bacteria in biofilms should motivate the search for other mechanisms of protection from killing by antimicrobial agents in biofilms.

Assessment of lectin-binding analysis for in situ detection of glycoconjugates in biofilm systems.

Abstract: An assessment of lectin-binding analysis for the characterization of extracellular glycoconjugates as part of the extracellular polymeric substances in environmental microbial communities was performed using fully hydrated river biofilms. The applicability of the method was evaluated for single, dual and triple staining with a panel of fluor-conjugated lectins. It was shown that lectin-binding analysis was able to stain glycoconjugates within biofilm communities. Lectin staining also demonstrated spatial heterogeneity within the biofilm matrix. Furthermore, the application of two or even three lectins was possible if suitable combinations were selected. The lectin-binding analysis can be combined with general nucleic acid stains to collect both nucleic acid and glycoconjugate signals. The effects of incubation time, lectin concentration, fluor labelling, carbohydrate inhibition, order of addition and lectin interactions were studied. An incubation time of 20 min was found to be sufficient for completion of lectin binding. It was not possible to ascertain saturating concentration for individual lectins, therefore a standard concentration was used for the assay. Carbohydrate inhibition tests indicated that fluorescein isothiocyanate (FITC)-conjugated lectins had more specific binding characteristics than tetramethyl rhodamine isothiocyanate (TRITC)- or cyanine dye (CY5)-labelled lectins. The order of addition and the nature of the fluor conjugate were also found to influence the binding pattern of the lectins. Therefore the selection of a panel of lectins for investigating the EPS matrix must be based on a full evaluation of their behaviour in the biofilm system to be studied. Despite this necessity, lectin-binding analysis represents a valuable tool to examine the glycoconjugate distribution in fully hydrated biofilms. Thereby, chemical heterogeneities within extracellular biofilm locations can be identified in order to examine the role (e.g. sorption properties, microenvironments, cell–extracellular polymeric subtance interactions) of the extracellular polymeric substances in environmental biofilm systems.

Phylogenetic and Functional Heterogeneity of Sediment Biofilms along Environmental Gradients in a Glacial Stream

Abstract: We used in situ hybridization with fluorescently labeled rRNA-targeted oligonucleotide probes concurrently with measurements of bacterial carbon production, biomass, and extracellular polymeric substances (EPS) to describe the bacterial community in sediments along a glacial stream. The abundance of sediment-associated Archaea, as detected with the ARCH915 probe, decreased downstream of the glacier snout, and a major storm increased their relative abundance by a factor of 5.5 to 7.9. Bacteria of the Cytophaga-Flavobacterium group were also sixfold to eightfold more abundant in the storm aftermath. Furthermore, elevated numbers of Archaea and members of the Cytophaga-Flavobacterium group characterized the phylogenetic composition of the supraglacial ice community. We postulate that glacial meltwaters constitute a possible source of allochthonous bacteria to the stream biofilms. Although stream water temperature increased dramatically from the glacier snout along the stream (3.5 km), sediment chlorophyll a was the best predictor for bacterial carbon production and specific growth rates along the stream. Concomitant with an increase in sediment chlorophyll a, the EPS carbohydrate-to-bacterial-cell ratio declined 11- to 15-fold along the stream prior to the storm, which is indicative of a larger biofilm matrix in upstream reaches. We assume that a larger biofilm matrix is required to assure prolonged transient storage and enzymatic processing of allochthonous macromolecules, which are likely the major substrate for microbial heterotrophs. Bacteria of the Cytophaga-Flavobacterium cluster, which are well known to degrade complex macromolecules, were most abundant in these stream reaches. Downstream, higher algal biomass continuously supplies heterotrophs with easily available exudates, therefore making a larger matrix unnecessary. As a result, bacterial carbon production and specific growth rates were higher in downstream reaches.

Influence of Algal Photosynthesis on Biofilm Bacterial Production and Associated Glucosidase and Xylosidase Activities.

Abstract: Natural photosynthetic biofilms were incubated under light (100 mmol m?2 s?1) and dark conditions to elucidate the impact of photosynthesis on bacterial production, abundance, biovolume, biomass, and enzyme activities over 24 h. Use of organic carbon-free media limited carbon sources to algal photosynthesis and possibly the polysaccharides of the biofilm matrix. Bacterial production of biofilm communities was significantly higher in light incubations (p < 0.001). The greatest differences in production rates between light and dark incubations occurred between 8 and 24 h. Biomass-specific a- and b-glucosidase and b-xylosidase activities were stimulated by photosynthesis, with significantly greater activities occurring at hours 16 and 24 in the light treatment (p < 0.01). The results indicate that algal photosynthesis can have a significant impact on bacterial productivity, biomass, biovolume, and enzyme production over longer time periods at low photon flux densities (?100 mmol m?2 s?1).

Effects of Photosynthesis on Bacterial Phosphatase Production in Biofilms.

Abstract: The fraction of bacteria displaying phosphatase activity within natural photosynthetic biofilms was examined in relation to phosphorus limitation and algal photosynthesis. An artificial substrate that forms a fluorescent precipitate was used in conjunction with the nucleic acid stain DAPI to enumerate extracellular phosphatase expression by biofilm bacteria exposed to different photosynthetic activities and phosphorus supplies. The proportion of bacteria displaying phosphatase activity changed in response to the presence or absence of algal photosynthesis. In general, phosphate-deprived biofilms had positive linear trends in bacterial phosphatase activity (p < 0.001), with greater proportions of bacteria displaying phosphatase under photosynthetic inhibition compared to active photosynthesis. Under sufficient phosphate supplies, biofilms had negative linear trends (p < 0.05) or were lower in the proportion of bacteria displaying phosphatase activity in the presence of algal photosynthesis, whereas bacterial phosphatase activity was generally maintained when photosynthesis was inhibited. It is suggested that the amount of extracellular organic carbon released within the biofilm matrix during photosynthesis indirectly affected bacterial phosphatase synthesis.

Laboratory evaluation of anti-biofilm agents for use in dental unit waterlines.

Abstract: Dental unit waterline biofilm has been recognized as a potential point of contamination and a risk to patients with any level of immunocompromise. Biofilm in dental unit waterlines, once established, has proven formidable to efforts in disinfection/disruption. This project compared standardized evaluation techniques by assessing the efficacy of a variety of agents that have been reported or suggested as useful in surface disinfection and/or antiseptic protocols. The zones of inhibition, minimum inhibitory/bactericidal concentrations and use-dilution with stainless steel carrier replicates tests assessed the disinfection of planktonic organisms using standardized microbial testing procedures. The disruption and/or disinfection of planktonic and biofilm organisms within naturally occurring dental unit waterlines were evaluated by culture and scanning electron microscopy. The six commercially available antimicrobial agents used to assess the techniques were bleach (sodium hypochlorite), Cavicide, glutaraldehyde, Listerine Antiseptic, Peridex and Sterilex Ultra. Comparisons between the results for each technique evaluated were determined for each product. All six agents demonstrated antimicrobial efficacy at the working concentrations designated by the manufacturers. Biofilm matrix elimination evaluated by scanning electron microscopy found virtually 0% elimination by glutaraldehyde to an estimated 90% elimination by Sterilex Ultra and bleach after one treatment. Treatment with Cavicide, Listerine Antiseptic and Peridex resulted in negligible elimination of the biofilm matrix. For comparability, the use of standardized testing techniques to evaluate a disinfection agent's efficacy against dental unit waterline contamination is essential. This project demonstrates a model system for evaluating disinfection agents potentially useful in the management of dental unit waterline biofilm, and should assist in educating the dental clinician in the appraisal of existing and future product claims.

Using dissolved and particulate carbon for the prediction

Abstract: Various investigations into soft sediment transport have shown recently that the growth of benthic microorganisms on cohesive sediments can influence the erosional behaviour of the bed material The formation of biofilms and microbial mats on mud banks has been reported to occur in estuaries and reservoirs Most benthic microorganisms produce and exudate extracellular polymeric substances (EPS) These exudates serve as connection between cells and sediment particles and form the amorphous biofilm matrix in which the organisms are embedded A variety of biological parameters (ie photopigment content, number of cells) has been used to correlate the biological status of the bed with the erodibility of the sediments This article deals with the utilization of dissolved and particulate organic carbon to perform this correlation Experiments were carried out in a small in-situ-device Biofilms (microbial mats respectively) consisting of pennate diatoms and filamentous cyanobacteria were established on a pure caolinite bed The shear stress was increased stepwise in order to ascertain the critical shear stress for erosion Particulate organic carbon (POC) was determined by means of a CHN-elemental analyzer Dissolved organic carbon (DOC) could be determined using phenol and sulfuric acid

Detection of streptococcal glucan-binding proteins in biofilms.

Abstract: Publisher Summary Extracellular and cell-bound glucosyltransferases (GTFs) produce α- 1,6 and/or α- 1,3 glucans from the sucrose. The glucans seem to be required for biofilm development because a-glucanases are able to suspend the adherent cells. Glucan-binding proteins contribute to the integrity of the biofilm matrix. The glucan-binding proteins (GBPs), including a glucan-binding lectin (GBL), appear to be both cell-associated and secreted. An enhanced chemiluminescence (ECL) method for GBPs developed by Galperin et al. is adapted to study sucrose-dependent biofilms of Streptococcus sobrinus. This chapter provides a schematic for the ECL method. Proteins were recovered from cells and supematants of planktonic cultures and biofilms, subjected to sodium dodecyl sulfate gel electrophoresis, and transferred onto polyvinylidene difluofide for ECL analysis. Biofilm cells contain numerous GBPs ranging in molecular weight from 40,000 to > 150,000. Supernatants of biofilm cultures had only one major protein, suggesting that most of the GBPs are involved in biofilm formation. The ECL technique allows for the detection of multiple GBPs and permits a rapid comparison between planktonic and biofilm conditions.

The role of exopolymers in Sphingomonas paucimobilis attachment and biofilm formation

Abstract: Eropolymers hm•e a11 importa111 IVIe ill biofilm formatioll, bei11g i11vo/ved i11 tire i11itial adhesio11 el'tiiiS and ilrflue11ci11g the biofilm characteristics. The results of a study with a strai11 of Sphingomonas paucimobilis that excretes a polysaccharide gum (gella11) has bee11 used to exemplify the role of exopo/ymers in cell attachme111 a11d biofilm formatioll . The attachment results were i11terpreted tluvugh the XDLVO theory a11d they revealed that exopolymers have a dual role i11 cell attachme111 by both coati11g the srcbstratum maki11g adhesiollfavourable a11d by stre11gthe11i11g adhesio11tluvuglr the establishme11t of polymeric bridges. Exopolymers \\"ere also esse11tialto the fomratioll of Spllingomonas paucimobilis biofilms acting as scaffolds for bacterialp1VIiferatimr. 11re plrysinwhemicalpmperties, tire nJI/IfWsititm of tl1e biofilm matrix cmcl tire colresimr fon:es ll"itlri11 tire /Jiojilm 1rere also ccmditio11ed by tl1e prese11ce of C'.l'llf'CJ{_I'JIIe/"S.