The role of the pH conditions of growth on the bioadhesion of individual and lawns of pathogenic Listeria monocytogenes cells

The work of adhesion that governs the interactions between pathogenic Listeria monocytogenes and silicon nitride in water was probed for individual cells using atomic force microscopy and for lawns of cells using contact angle measurements combined with a thermodynamic-based harmonic mean model. The work of adhesion was probed for cells cultured under variable pH conditions of growth that ranged from pH 5 to pH 9. Our results indicated that L. monocytogenes cells survived and adapted well to the chemical stresses applied. For all pH conditions investigated, a transition was observed in the generation time, physiochemical properties, biopolymer grafting density and bioadhesion for cells cultured in media adjusted to pH 7 of growth. In media with pH 7, the generation time for the bacterial cells was lowest, the specific growth rate constant was highest, the cells were the most polar, cells displayed the highest grafting density of surface biopolymers and the highest bioadhesion to silicon nitride in water represented in terms of the work of adhesion. When compared, the work of adhesion values quantified between silicon nitride and lawns of L. monocytogenes cells were linearly correlated with the work of adhesion values quantified between silicon nitride and individual L. monocytogenes cells.

The AFM and macroscale work of adhesion quantified between individual or lawns of L. monocytogenes cells and Si3Ni4, respectively as a function of the pH of growth.Figure optionsDownload high-quality image (70 K)Download as PowerPoint slideHighlights
► The work of adhesion for individual bacterial cells was measured using AFM.
► The work of adhesion for lawns of bacteria was quantified based on contact angles.
► The two types of work of adhesion were found to be linearly correlated.
► All bacterial cells adapted to chemical stress.