This work is concerned with investigating the effect of substrate hydrophobicity and surface potential on the dynamics of initial phases of bacterial adhesion. To this end, the foodborne bacterial pathogens Staphylococcus aureus and Escherichia coli O157:H7 as model Gram-positive coccoid and Gram-negative bacilli microbes were applied to molecularly smooth self-assembled monolayer surfaces with precisely controlled surface coverage and chemistry. The resultant substrates had a static water contract angles in the range of ~50-110° and zeta potential of -48 to +10 mV. While interfacial properties of substrates and microorganisms were extensively characterized using laser Doppler electrophoresis, streaming potential technique, and contact angle goniometry, the numbers and distributions of adherent bacteria were quantified through high-resolution scanning electron microscopy. Bacterial adhesion was greatest on hydrophilic surfaces with positive zeta potential, followed by hydrophobic surfaces with increasing hydrophobicity, and the smallest on hydrophilic surfaces with negative zeta potential. The time constant of adhesion was about two to four times greater for E. coli O157:H7 compared to S. aureus, indicating a lower number attached per unit time for E. coli O157:H7 but a comparable mass attached per unit time due to the difference in size of these species. A transition from a power-law to exponential time-dependency was observed upon changing surfaces from hydrophilic surfaces with positive zeta potential to hydrophobic surfaces and hydrophilic surfaces with negative zeta potentials.

New insights into kinetics and dynamics of initial stages of bacterial adhesion onto surfaces mimicking food crops

255th National Meeting (2018)

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