Fundamental Study of Adhesion Mechanisms of Bacteria from Different Environments.

The purpose of this project was to quantitatively and qualitatively evaluate the adhesion of microbes from different environments. This project is based on the hypothesis that microbes from different environments exhibit varied and unique adhesion behavior, due to differences in cell surface characteristics and cellular constituency. The objective and main goal of this project was to investigate the adhesion of four strains of bacteria from different environments, using a Parallel-Plate Flow chamber. The microbial strains utilized in this study included: Escherichia coli HB101, a non-infectious bacillus-shaped enteric bacterium; Pseudomonas aeruginosa PA01, a pathogenic (opportunistic) bacillus-shaped nosocomial bacterium; Shewanella putrefaciens CN38, a non-infectious bacillus-shaped metal-reducing bacterium, and , Candida parapsilosis ATC90018, a pathogenic (opportunistic) coccus-shaped biomedical fungus. Each microbial strain was diluted in 0.01 M Phosphate Buffer Solution (PBS), and was pulsed through the Parallel-Plate Flow Chamber in silicon tubing, using a peristaltic pump. The flow cell reservoir was pulsed through the Flow Chamber at an average rate of 17 mL/min at pH=7.4, under laminar flow conditions at room temperature. The adhesion of microbes to the biomaterial glass slide of the flow cell was determined for each strain using fluorescence microscopy at 100X magnification, a SPOT imaging computer program and hand-counting techniques. All data pertaining to adhesion within the flow cell was normalized to that of data obtained by studying adhesion to porous filter slides. It was determined that the fungal strain, Candida parapsilosis ATCC90018, possessed the greatest adhesion affinity towards the biomaterial sample within the flow cell. This may be due to the fact that the Candida strain is the largest in size, with a relatively uniform surface area, and possesses substantial attractive forces, allowing for a greater probability of adhesion. In addition, the Candida strain possessed the lowest diffusivity coefficient, perhaps allowing the fungal strain to remain in contact with the biomaterial slide throughout experimentation, in addition to causing settling phenomena. Escherichia coli HB101 and Pseudomonas aeruginosa PA01 displayed the lowest adhesion affinities of this study. This may be due to the fact that both of these strains possess much smaller cellular diameters than the Candida strain, in addition to the fact that they possess bacillus-like shape, high diffusivity coefficients, and hydrophilic properties. Shewanella putrefaciens CN38 displayed a medial or intermediate adhesion affinity as compared to the other strains. It is believed that this type of adhesion behavior is a direct result of the medial diffusivity coefficient, intermediate size, and metal-reducing qualities, possessed by the Shewanella strain. Thus, based on data analysis, the underlying hypothesis has been verified: bacteria from different environments do exhibit varied adhesion characteristics due to differences in size, diffusive and hydrophobic properties, and cellular constituencies