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An oxalate-fermenting brown rot fungus, Fomilopsis palustris, secretes large amounts of oxalic acid during wood decay. Secretion of oxalic acid is indispensable for the degradation of wood cell walls, but almost nothing is known about the transport mechanism by which oxalic acid is secreted from F. palustris hyphal cells. We characterized the mechanism for oxalate transport using membrane vesicles off", palustris. Oxalate transport in F. palustris was ATP dependent and was strongly inhibited by several inhibitors, such as valinomycin and NH4+, suggesting the presence of a secondary oxalate transporter in this fungus. We then isolated a cDNA, FpOAR (Fomitopsis palustris oxalic acid resistance), from F. palustris by functional screening of yeast transformants with cDNAs grown on oxalic acid-containing plates. FpOAK is predicted to be a membrane protein that possesses six transmembrane domains but shows no similarity with known oxalate transporters. The yeast transformant possessing FpOAR (fpO/lif-transformant) acquired resistance to oxalic acid and contained less oxalate than the control transformant. Biochemical analyses using membrane vesicles of the FpOAR-trans-formant showed that the oxalate transport property of FpOAR was consistent with that observed in membrane vesicles off. palustris. The quantity of FpOAR transcripts was correlated with increasing oxalic acid accumulation in the culture medium and was induced when exogenous oxalate was added to the medium. These results strongly suggest that FpOAR plays an important role in wood decay by acting as a secondary transporter responsible for secretion of oxalate by F. palustris. [ABSTRACT FROM AUTHOR]

Shear-enhanced adhesion, although not observed for fimbria-mediated adhesion of oral Actinomyces spp., was noted for Hsa-mediated adhesion of Streptococcus gordonii to sialic acid-containing receptors, an interaction implicated in the pathogenesis of infective endocarditis. [ABSTRACT FROM AUTHOR]

Bacterial bioflims cause numerous problems in health care and industry; notably, biofllms are associated with a large number of infections. Biofilm-dwelling bacteria are particularly resistant to antibiotics, making it hard to eradicate biofilm-associated infections. Bacteria rely on efflux pumps to get rid of toxic substances. We discovered that efflux pumps are highly active in bacterial bioflims, thus making efflux pumps attractive targets for antibiofllm measures. A number of efflux pump inhibitors (EPIs) are known. EPIs were shown to reduce biofllm formation, and in combination they could abolish biofllm formation completely. Also, EPIs were able to block the antibiotic tolerance of biofllms. The results of this feasibility study might pave the way for new treatments for biofllm-related infections and may be exploited for prevention of biofllms in general. [ABSTRACT FROM AUTHOR]

Spores from four Geobacillus spp. were isolated from a milk powder manufacturing line in New Zealand. Liquid sporulation media produced spore yields of ∼107 spores ml-1; spores were purified using a two-phase system created with polyethylene glycol 4000 and 3 M phosphate buffer. The zeta potentials of the spores from the four isolates ranged from -10 to -20 mV at neutral pH, with an isoelectric point between pH 3 and 4. Through contact angle measurements, spores were found to be hydrophilic and had relative hydrophobicity values of 10 to 40%, as measured by the microbial adhesion to hexadecane assay. The most hydrophilic spore isolate with the smallest negative charge attached in the highest numbers to Thermanox and stainless steel (1 × 104 spores cm-2), with fewer spores attaching to glass (3 × 10³ spores cm-2). However, spores produced by the other three strains attached in similar numbers (P > 0.05) to all substrata (∼1 × 10³ spores cm-2), indicating that there was no simple relationship between individual physicochemical interactions and spore adherence. Therefore, surface modifications which limit the attachment of one strain may not be effective for all stains, and control regimens need to be devised with reference to the characteristics of the particular strains of concern. [ABSTRACT FROM AUTHOR]

Previous studies have described both surface morphology and adhesive properties of fungal spores, but little information is currently available on their mechanical properties. In this study, atomic force microscopy (AFM) was used to investigate both surface topography and micromechanical properties of Aspergillus nidulans spores. To assess the influence of proteins covering the spore surface, wild-type spores were compared with spores from isogenic rodA+ and rodA- strains. Tapping-mode AFM images of wild-type and rodA+ spores in air showed characteristic "rodlet" protein structures covering a granular spore surface. In comparison, rodA- spores were rodlet free but showed a granular surface structure similar to that of the wild-type and rodA+ spores. Rodlets were removed from rodA+ spores by sonication, uncovering the underlying granular layer. Both rodlet-covered and rodlet-free spores were subjected to nanoindentation measurements, conducted in air, which showed the stiffnesses to be 110 ± 10, 120 ± 10, and 300 ± 20 N/m and the elastic moduli to be 6.6 ± 0.4, 7.0 ± 0.7, and 22 ± 2 GPa for wild-type, rodA+ and rodA- spores, respectively. These results imply the rodlet layer is significantly softer than the underlying portion of the cell wall. [ABSTRACT FROM AUTHOR]

Viral inactivation and adhesion-aggregation in water are often studied as separate phenomena. When the focus is placed on viral adhesion-aggregation, inactivation is neglected because the phenomena under investigation occur over a short period measured in days. When viral inactivation is studied, adhesion-aggregation phenomena are considered to be negligible because viral survival is traced over several days or months. In the present work, we took a global approach, examining the relative contributions of each of these processes in a complex system composed of groundwater, Poliovirus 1, and a hydrophobic container (polypropylene) maintained in a dark environment at 20°C. We demonstrated that infectious viral load fell off 2.8 log10 during the first 20 days. During this time, adhesion was far from negligible because it accounted for most of the decline, 1.5 log10. Adhesion was undoubtedly favored by the presence of divalent ions in the groundwater. After 20 days, aggregation may also have been the cause of 0.66 to 0.92 log10 of viral loss. Finally, viral inactivation was quantitatively the lowest phenomena because it only explained 0.38 to 0.64 log10 of the viral loss. This study thus clearly demonstrated that estimates of viral survival in a given system must always take into account adhesion-aggregation phenomena which may be responsible for the majority of viral loss in the aqueous phase. Adhesion and aggregation are reversible processes which may lead to an underestimation of viral load in certain studies. [ABSTRACT FROM AUTHOR]

Microbial infections of medical implants occur in more than 2 million surgical cases each year in the United States alone. These increase patient morbidity and mortality, as well as patient cost and recovery time. Many treatments are available, but none are guaranteed to remove the infection. In many cases, the device infections are caused by the adhesion of microbes to the implant, ensuing growth, pathogenesis, and dissemination. The purpose of this work is to examine the initial events in microbial adhesion by simulating the approach and contact between a planktonic cell, immobilized on an atomic force microscope (AFM) cantilever, and a biomaterial or biofilm substrate. The two model microbes used in this study, Candida parapsilosis (ATCC 90018) and Pseudomonas aeruginosa (ATCC 10145), were chosen for both their clinical relevance and their ease of acquisition and handling in the laboratory setting. Attractive interactions exist between C. parapsilosis and both unmodified silicone rubber and P. aeruginosa biofilms. Using C. parapsilosis cells immobilized on AFM cantilevers with a silicone substrate, we have measured attractive forces of 4.3 ± 0.25 nN in the approach portion of the force cycle. On P. aeruginosa biofilms, the magnitude of the attractive force decreases to 2.0 ± 0.40 nN and is preceded by a 2.0-nN repulsion at approximately 75 nm from the cell surface. These data suggest that C. parapsilosis may adhere to both silicone rubber and P. aeruginosa biofilms, possibly contributing to patient morbidity and mortality. Characterization of cell-biomaterial and cell-cell interactions allows for a quantitative link between the physicomechanical and physicochemical properties of implant materials and the nanoscale interactions leading to microbial colonization and infection. [ABSTRACT FROM AUTHOR]

The adhesion of nonflagellated Escherichia coli strain K-12 to polystyrene (PS) latex spheres or glass capillaries has been observed by using several techniques. Attention was focused on the orientation of the rod-shaped bacteria as they adhered to the surfaces in 100 mM phosphate-buffered saline. Data show that PS particles adhered to the ends of the bacteria more than 90% of the time. Moreover, the PS particles adhered to one end only, never to both. Similarly, for experiments with bacteria adhering to glass, the bacteria adhered on their ends. In order to determine whether the end of a bacterium had a different charge density from that of the middle, rotational electrophoresis experiments were used. These experiments indicated no measurable charge nonuniformity. In order to examine how strongly adhered the bacteria were to the PS particles, differential electrophoresis was used. Almost always, bacteria were found to be irreversibly adhered to the PS spheres. The cause of the oriented adhesion is not likely due to surface lipopolysaccharides (LPS), since the three strains of K-12 that were used, each having a different length of LPS, showed similar behavior. The results are discussed in terms of bacterial cell polarity. The data indicate that nanodomains on the bacterial ends are important for adhesion and that the time scale for irreversible adhesion is short. [ABSTRACT FROM AUTHOR]

Flow chambers are commonly used to study microbial adhesion to surfaces under environmentally relevant hydrodynamic conditions. The parallel plate flow chamber (PPFC) is the most common design, and mass transport occurs through slow convective diffusion. In this study, we analyzed four different PPFCs to determine whether the expected hydrodynamic conditions, which control both mass transport and detachment forces, are actually achieved. Furthermore, the different PPFCs were critically evaluated based on the size of the area where the velocity profile was established and constant with a range of flow rates, indicating that valid observations could be made. Velocity profiles in the different chambers were calculated by using a numerical simulation model based on the finite element method and were found to coincide with the profiles measured by particle image velocimetry. Environmentally relevant shear rates between 0 and 10,000 s[sup -1] could be measured over a sizeable proportion of the substratum surface for only two of the four PPFCs. Two models appeared to be flawed in the design of their inlets and outlets and allowed development of a stable velocity profile only for shear rates up to 0.5 and 500 s[sup -1]. For these PPFCs the inlet and outlet were curved, and the modeled shear rates deviated from the calculated shear rates by up to 75%. We concluded that PPFCs used for studies of microbial adhesion to surfaces should be designed so that their inlets and outlets are in line with the flow channel. Alternatively, the channel length should be increased to allow a greater length for the establishment of the desired hydrodynamic conditions. [ABSTRACT FROM AUTHOR]

Discusses the plasticizers increase adhesion of the deteriogenic fungus Aureobasidium pullulans to polyvinyl chloride. Effect of substratum hydrophobicity on adhesion; Influence of electrolyte concentration on adhesion to pPVC and uPVC; Influence of pH on blastospore cell surface charge.

Assesses cell surface charge and hydrophobicity and adhesion to polystyrene, glass, and barley for wild-type Rhodosporidium toruloides and attachment-minus mutants. Decrease in hydrophobicity and adhesiveness of wild-type R. toruloides from mid-log to late stationary phase; Role of localized, positive charge in mediating attachment.

Studies the adhesion of Acinetobacter venetianus VE-C3 to diesel fuel and n-hexadecane and compares it to that of Acinetobacter sp. strain RAG-1, which is known to excrete the emulsifying lipopolysaccharide, emulsan. Production of capsular polysaccharides; Type types of adhesion of VE-C3; Average signal frequency and film formation times.

Presents a study on adhesion mutant that had decreased adhesion ability and increased transport potential compared with the wild-type using a trichlorethylene (TCE)-degrading strain of Burkholderia cepacia. Cell surface characteristics responsible for the altered transport properties; Materials and methods of the study; Results of the study.