The ability of Candida albicans and Candida spp. to adhere to inert polymeric surfaces may allow these organisms direct ingress into the human host. Biophysical characterization of this adherence shows that the forces responsible for such adherence are attractive London-van der Waals forces (or hydrophobic forces) and electrostatic forces. The hydrophobic affinity of yeasts was determined by (i) a water-hydrocarbon two-phase assay and by (ii) measurement of the contact angle (theta) of a liquid droplet on a monolayer of yeast cells. The hydrophobicity of the yeasts correlated with the tendency of yeasts to adhere to polystyrene and was reduced in the presence of Tween 20. The adherence of yeasts to polymers of increasing hydrophobicity (determined by the contact angle method) was directly proportional to theta. Yeast surface charges were altered by selectively blocking amino and carboxyl groups. The more positively charged yeasts adhered in greater numbers. Increasing the molarity of NaCl increased yeast adherence. These forces probably contribute to the negative cooperativity (determined by Scatchard and Hill plot) that characterizes the adherence of yeasts to polymers.

No abstract

No abstract

An enrichment culture procedure has been used to isolate mixed culture systems which grow upon “Bunker C” fuel oil. When inoculated into a mineral salts aqueous medium containing Bunker C oil, the mixed cultures initiate oil emulsification. Emulsification usually is observed in 24–48 hr. The role of microbes in this emulsification will be discussed. It appears that certain metabolic products produced by the microbe possess properties of surfactants. Bacteria and fungi have been isolated which possess the ability to cause emulsification. Freeze‐dried biomass is also capable of emulsifying oil. Chromatographic analyses of biodegraded Bunker C fuel oil show that microorganisms selectively metabolize the n‐paraffin fraction.

An extracellular polymer was produced by continuous fermentation of Corynebacterium hydrocarboclastus on kerosene in a 24 liter reactor. This polymer was composed of protein, lipid, and carbohydrates. The polymer possessed surface active properties, and had two critical micelle concentrations. Its effectiveness was quite comparable to the effectiveness of synthetic surface active agents such as Tween 80 and Span 20; however, its efficiency was much lower. The polymer also had emulsifying properties. Maximum emulsification was obtained at pH 6. The emulsifying properties were unaffected by high salt concentration [up to 5% (w/v) in Na+], and tolerated a water hardness up to 5,000 ppm. A 2 hr treatment of the polymer at temperatures higher than 65 degrees C resulted in a loss of its emulsifying properties. Two microorganisms, named SLYS and Y, isolated from soil, were able to grow on the polymer as sole carbon and energy source, thus proving its biodegradability. SLYS was tentatively identified as Flavobacterium breve and Y as Flavobacterium devorans.