Abstract
The attachment of Staphylococcus epidermidis to the surface of carbon paste electrode (CPE) by applying positive potentials (50 - 600 mV) with regard of various buffer pH, cultivation time and solid-medium type was studied. The attachment process was analyzed by measuring the electric current derived from the dye (amido black) adsorbed on the vacant areas of CPE after attachment of microbial cells. The pH was not identified as a single main factor affecting the attachment (p > 0.05), however further insight revealed that the potentials applied had different effects on the microbial cells attachment. Both cultivation time and solid-medium type significantly affected the microbial attachment. Generally, increase of cultivation time up to 168 h resulted in increase of adhesion. Applying potentials 300, 400 and 200 mV resulted in the highest attachment process for bacteria cultivated for 24, 48 and 168 h, respectively. S. epidermidis cultivated on the blood agar and Baird-Parker agar plates showed the higher extent of attachment.
Highlights
The surface characteristics of bacterial cells including hydrophobicity, surface charge and electron donor/acceptor properties play an important role in their attachment to various surfaces
In acidic environment, the attachment of bacterial cells to the surface of the carbon paste electrode (CPE) was slightly en hanced at 50 and 100 mV in comparison with that occurred during free attachment process (p < 0.05) in our study
It has to be noticed that bacteria were still viable at the end of the attachment process in all the buffer solutions and the cells concentration did not differ from the initial count (p < 0.05)
Summary
The surface characteristics of bacterial cells including hydrophobicity, surface charge and electron donor/acceptor properties play an important role in their attachment to various surfaces. Microorganisms acquire a surface electric charge in aqueous environment due to the ionization of their surface chemical groups, such as amino, carboxyl and phosphoryl groups. While hydrophobic interactions between hydrophobic molecules on the surface of the microorganism cells and the inert surface predominate at long distance (cca 10 nm), the electric surface charge acted at shorter distances [4]. Physiological state of the bacterial cells and the pH of the surrounding environment play a crucial role in attachment process [5,6,7,8,9,10]
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