Factors influencing the detachment of a polymer-associated Acinetobacter sp. from stainless steel

The role of an extracellular polymer secreted by an Acinetobacter sp. attached to stainless steel was investigated. Parameters expected to influence polymer conformation, viz. temperature, pH, ionic strength and the concentration of calcium and magnesium ions, were altered and the resulting detached bacteria enumerated. Increasing both the temperature and pH resulted in increased numbers of bacteria detached. The effects of increasing the concentration of sodium chloride up to 100 mM and magnesium or calcium chloride up to 30 mM were small and, although statistically significant, were considered unlikely to have had major influence on the association of the bacteria with the stainless steel surfaces. Treatments including ultraviolet irradiation of surface-associated bacteria always resulted in removal of greater numbers of bacteria when compared to treatments where irradiation was not employed. The results indicate that an adhesive extracellular acidic polysaccharide may mediate the attachment of the Acinetobacter sp. to stainless steel.