Influence of protein conditioning films on binding of a bacterial polysaccharide adhesin from Hyphomonas MHS-3

Biochemical composition of the marine conditioning film: implications for bacterial adhesion

The conditioning film formed on glass panels was analysed for total carbohydrates (CFCHO), total proteins (CFP) and total uronic acids (CFURA). The influence of these compounds on the adhesion of three marine bacterial cultures, Pseudomonas sp. CE-2, Pseudomonas sp. CE-10 and Bacillus sp. SS-10 was also evaluated. One-way analysis of variance suggested a significant increase in the attachment of all three cultures to conditioned glass panels. Moreover, CE-2 (r = 0.874) and CE-10 (r = 0.879) showed a significant positive correlation with CFCHO. Conversely, SS-10 (r = -0.69) showed a significant negative correlation with CFCHO. Backward multiple linear regression analysis indicated that CFCHO were the most predictive component of the conditioning film in explaining bacterial adhesion to the conditioned glass panels.

Action of chlorhexidine digluconate against yeast and filamentous forms in an early-stage Candida albicans biofilm

An in situ method for sensitive detection of differences in the action of chlorhexidine against subpopulations of cells in Candida albicans biofilms is described. Detection relies on monitoring the kinetics of propidium iodide (PI) penetration into the cytoplasm of individual cells during dosing with chlorhexidine. Accurate estimation of the time for delivery of the dosing concentration to the substratum was facilitated by using a flow cell system for which transport to the interfacial region was previously characterized. A model was developed to quantify rates of PI penetration based on the shape of the kinetic data curves. Yeast were seeded onto the substratum, and biofilm formation was monitored microscopically for 3 h. During this period a portion of the yeast germinated, producing filamentous forms (both hyphae and pseudohyphae). When the population was subdivided on the basis of cell morphology, rates of PI penetration into filamentous forms appeared to be substantially higher than for yeast forms. Based on the model, rates of penetration were assigned to individual cells. These data indicated that the difference in rates between the two subpopulations was statistically significant (unpaired t test, P < 0.0001). A histogram of rates and analysis of variance indicated that rates were approximately equally distributed among different filamentous forms and between apical and subapical segments of filamentous forms.

Time-of-flight secondary ion mass spectrometry: characterisation of stainless steel surfaces immersed in natural seawater

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been employed to study the biofouling of stainless steel samples immersed in seawater. The aim of these characterisations was to understand the initial mechanisms of biomolecule adsorption for relatively short immersion times (from 0 to 24 h). The results show that: (i) there were unavoidable sample "precontaminations" on the surfaces, despite precaution during their preparation and manipulation (washing, drying and storing); (ii) the major peaks detected were the substrate ones whatever the immersion time [However, some organic (nitrogen and oxygen containing) and inorganic secondary ions appeared and grew with the immersion time.]; (iii) the surface contaminations, the nonuniformity of the adsorbed material so as and bacteria have been clearly observed by high-lateral resolution molecular ToF-SIMS mapping.

Integration of Raman microscopy, differential interference contrast microscopy, and attenuated total reflection Fourier transform infrared spectroscopy to investigate chlorhexidine spatial and temporal distribution in Candida albicans biofilms

Two spectroscopic techniques, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and Raman microscopy (RM), were used to characterize transport of chlorhexidine digluconate (CHG) in Candida albicans (CA) biofilms. Different (volumetric) regions of the biofilm are sampled by these two vibrational spectroscopies making them complementary techniques. Simple mathematical models were developed to analyze ATR-FTIR and RM data to obtain an effective diffusion coefficient describing transport through CA biofilms. CA biofilms were composed primarily of yeast and hyphal forms, with some pseudohyphae. Upper regions of biofilms that had become confluent, (i.e., biofilms that completely covered the germanium (Ge) substratum) were composed primarily of a tangled mass of hyphae with openings between germtubes about 10 to 50 microm across. Quantitative analysis of ATR-FTIR kinetic data curves indicated that the effective diffusion coefficient for transport of CHG through confluent biofilms about 200-microm thick was reduced 0.1 to 0.3 times compared to the diffusion coefficient for CHG in water. Effective diffusion coefficients obtained from analysis of RM data were consistently higher than those indicated by ATR-FTIR data suggesting that transport is more hindered in regions near the base of the biofilm than in the outer layers. Analysis of both ATR-FTIR and RM data obtained from thicker films indicated that adsorption of CHG to biofilm components was responsible for a substantial portion of the transport limitation imposed by the biofilm. Comparison of ATR-FTIR and RM data for both types of biofilms indicated that sites of CHG adsorption were more concentrated in the interfacial region than in the bulk biofilm. Comparison of results for ATR-FTIR and RM measurements suggests that these relatively thick CA biofilms can be modeled, for purposes of predicting transport, approximately as a homogeneous thin planar sheet. Thus, these biofilms offer a relatively tractable model system for initial investigations of the relation between antimicrobial transport and kinetics of antimicrobial action.

Influence of calcium and other cations on surface adhesion of bacteria and diatoms: A review

Association with a surface is an important aspect of survival for microorganisms in natural and manmade environments/Both bacteria and diatoms are involved in such associations. In many cases, this leads to surface fouling, which often results in surface deterioration and mechanical failure in industrial systems. We now know that microorganisms exploit many strategies to establish associations with surfaces. As in the case of other cellular processes, calcium ions seem to play an important role in adhesion of cells to surfaces. Calcium is involved in non-specific interactions such as neutralization of the electrical double layer between cell and substratum surface as well as specific adhesive interactions that cannot be replaced by other cations. The unique properties of calcium ions promote both specific and non-specific interactions with protein and polysaccha-ride adhesin molecules at the cell surface. As important, but less well understood, calcium ions also influence the way microbial cells interact with different substrata.

Influence of Divalent Cations and pH on Adsorption of a Bacterial Polysaccharide Adhesin

Hyphomonas MHS-3 (MHS-3) elaborates a diffuse capsular material, primarily composed of polysaccharide, which has been implicated to serve as the holdfast of this prosthecate marine bacterium. A purified polysaccharide (fr2ps) from this capsular material exhibits a relatively large affinity for (Ge), or more precisely for the Ge oxide surface film. In its natural habitat MHS-3 attaches to marine sediments. This suggests that molecular properties of fr2ps have evolved to render it adhesive toward mineral oxides. In order to characterize these molecular interactions, the effect of divalent cations and pH on the adsorption of fr2ps to Ge has been measured using attenuated total internal reflection Fourier transform infrared (ATR/FT-IR) spectroscopy. The effect of adsorption of fr2ps on the Ge oxide film has been investigated using X-ray photoelectron spectroscopy (XPS). The results indicate that divalent cations participate in binding of fr2ps to Ge oxide and that atomic size of the cation is important. Evidence for significant participation of hydrogen bonding to the oxide surface is lacking. Copyright 1998 Academic Press.

Combined light microscopy and attenuated total reflection fourier transform infrared spectroscopy for integration of biofilm structure, distribution, and chemistry at solid-liquid interfaces

Reflected differential interference contrast microscopy and attenuated total reflection Fourier transform infrared spectroscopy were used to obtain complementary data on the structural and chemical properties of a biofilm. This information was obtained nondestructively, quasisimultaneously, and in real time, thereby permitting the verification of time-dependent relationships between the biofilm's population structure, distribution, and interfacial chemistry. The approach offers opportunities to examine these relationships on a variety of substrata in the presence of a bulk aqueous phase under controlled hydrodynamic conditions.

Adhesion of biofilms to inert surfaces: A molecular level approach directed at the marine environment

Protein/ligand interactions involved in mediating adhesion between microorganisms and biological surfaces have been well-characterized in some cases (e.g. pathogen/host interactions). The strategies microorganisms employ for attachment to inert surfaces have not been so clearly elucidated. An experimental approach is presented which addresses the issues from the point of view of molecular interactions occurring at the interface.