Cultivation in different growth media affects the expression of the cell surface hydrophobicity of bacteria

Abstract

Environmental factors may greatly influence the expression of cell surface components of bacterial pathogens. Few studies have described the effect of growth conditions on the cell surface hydrophobicity of bacterial isolates of certain Gramnegative and Gram-positive bacteria. The present study describes the effects of CUltivation in four common liquid growth media on the cell surface hydrophobicity of non-clinical Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus using the microbial adhesion to hydrocarbon (MATH) test which assesses the partition of bacterial cells into a hydrocarbon phase. It was observed that growth in all the test media yielded cells with varying surface hydrophobicity increasing in the order: nutrient broth<tryptic soy broth<brain heart infusion broth<MacConkey broth, irrespective of the test strain. The changes were however, more pronounced in the Gram-positive strain. It was also observed that the surface of Staphylococcus aureus was more hydrophobic than that of Escherichia coli, irrespective of the cultivation media. The outcome of this work further point to the fact that environmental changes can influence cell surface hydrophobicity of bacteria which in turn can affect their adhesion to certain kinds of host targets through hydrophobic interactions.

Key words: Hydrophobicity; Escherichia coli; Staphylococcus aureus; Growth media