You are here:
Microbial cell surface characteristics: Elucidating attachment/detachment using hydrophobicity and electrokinetic measurements
Citation:
White, C., J. Popovicic, AND D. Lytle. Microbial cell surface characteristics: Elucidating attachment/detachment using hydrophobicity and electrokinetic measurements. Presented at 2013 AWWA ACE, Denver, CO, June 09 - 12, 2013.
Impact/Purpose:
The addition of chemical coagulants destabilizes suspended cells by disrupting their surface charge and causing them to aggregate and leave the water phase. In order to describe the potential interactions of several microorganisms during the process of drinking water treatment, the surface hydrophobicity and electrophoretic mobility of pure cultures was measured under different water chemistry conditions.
Description:
The surface properties of microorganisms play an important role in their behavior within the environment. Electrophoretic mobility and cell surface hydrophobicity of bacterial cells influence their initial interaction with surfaces and mediate their stability within an aqueous suspension. The effectiveness of a number of commonly used drinking water techniques are directly related to these surface properties. Most drinking water treatment methods rely on either the physical removal of bacterial cells through filtration, or the destabilization of the suspended cells through the addition of an inorganic cationic chemical coagulant. The initial interaction of bacterial cells with the filter media is dependent on both the surface hydrophobicity of the cells and the magnitude of their surface charge. The addition of chemical coagulants destabilizes suspended cells by disrupting their surface charge and causing them to aggregate and leave the water phase. In order to describe the potential interactions of several microorganisms during the process of drinking water treatment, the surface hydrophobicity and electrophoretic mobility of pure cultures was measured under different water chemistry conditions. In this study electrophoretic light scattering and microbial adhesion to hydrocarbon was used to measure the electrophoretic mobility and hydrophobicity of endospores of 6 Bacillus species and vegetative cells of V. cholarae, E. coli, Mycobacterium, Cryptosporidium, and B. cereus. Cells were measured in aqueous solution across a range of pH and ionic strengths. For the microbial adhesion to hydrocarbon (MATH) assay, Octane and Hexadecane were used as the hydrocarbon phase. Results suggest that surface charge is a unique trait among the species tested. Electrophoretic mobilities formed patterns supporting 16S rRNA gene phylogeny. The data show pH dependence of spore electrophoretic mobility below pH 6. The point zero charge of all spores tested generally fell below pH 3. Electrophoretic mobilities were less negative in high ionic strength solutions compared to low ionic strength solutions. Vegetative cell electrophoretic mobility was negative at pH 8 across ionic strength. Hydrophobicity of spores did not trend with electrophoretic mobility or 16S rRNA phylogeny at pH 8 in the buffer tested. Vegetative cell hydrophobicity generally correlated to electrophoretic mobility. Specifically, high hydrophobicity was typically consistent with a near neutral charge. Further research is needed to elucidate the effect of natural organic matter on EPM as well as matrix interaction studies to evaluate the data presented here. The data will be presented in the context of microbial surface characteristics’ influence on drinking water treatment processes.
URLs/Downloads:
http://www.awwa.org/conferences-education/conferences/ace13-annual-conference/hotel-travel/ace13-conference-program.aspx