Introduction: The impact of biofilms could be seen everywhere. Adhesion is the first phase of the development of biofilm. The properties of the surface, bacteria and medium (to whom they are exposed) affect the adhesion. The properties of the bacteria are: hydrophobicity, surface charge and physiological state of growth. The attached bacteria could be removed from surface also by changing the shear stress – hydrodynamic conditions. Purpose: The purpose of this study was to determine the optimal growth phase of the bacteria in which the adhesion of Bacillus subtilis is most effective. The aim was also to find out if the attached bacteria could be removed with the help of laminar flow regime. Methods: First we determined the quantity of the bacteria cells that were attached to copper coins in static conditions. After that we determined the impact of the shear stress on the adhered bacteria. The experiments were carried out using a flow chamber which created a laminar flow regime. The bacterial cells were observed by fluorescence microscopy. We also made a growth curve. Results: The adhesion of Bacillus subtilis was highest in the stationary physiological growth phase. Statistically, the physiological phase of the growth of bacterial culture significantly affects the attachment of the bacteria. We also found that there was a statistically significant difference between exposure to static conditions and the laminar flow regime. Discussion and conclusion: With our results, we did not confirm the hypothesis that the attachment of Bacillus subtilis is greatest in the exponential growth phase, as we have found that the most intense adhesion is in the stationary phase. On the basis of our findings, we can confirm the second hypothesis, because the laminar flow did remove the majority of the fixed cells. The difference between the static conditions and the maximum laminar flow regime was statistically significant.
|
