15A-20 |
Quantitative characterization of cell surface properties of bioluminescent E. coli |
Y. F. CHU, Dept. of Animal & Food Sciences, Univ. of Delaware, 040 Townsend Hall, 531 S. College Ave., Newark, DE 19717-1303 and Y. M. Lo, University of Delaware. Bioluminescent E. coli, as intended, is capable of emitting bioluminescence in response to hazardous inducers such as toxins and alcohols and hence could be used as the sensing element in detecting the presence of those detrimental substances. To leverage their applicability, it is vital to establish effective immobilization mechanism such as covalent bonding or adsorption, which keeps the contact between the supporting matrixes with cell surfaces to the minimal and hence sustains cell viability without sacrificing its sensitivity. Crucial to the selection of crosslinking agents or adsorption matrixes for effective cell immobilization, cell surface properties have to be determined. The objective of this study was to characterize the surface charge and hydrophobicity of bioluminescent E. coli as compared to their parental strain. Two bioluminescent strains, E. coli DPD-2224 and 2234, obtained from DuPont Microbial Genetics Lab (Wilmington, DE) were used. Their parental strain, E. coli mm28, was obtained from the E. coli Genetic Stock Center (New Haven, CT). Zeta potential, which measures the electrophoretic mobility of cells, was used to characterize their surface charge. The microbial adhesion to hydrocarbon (MATH) method was used to assess cell surface hydrophobicity. The values of zeta potential of E. coli mm28, DPD-2224, and 2234 at exponential/stationary phase were -41.11/-45.08, -30.58/-35.69, and -32.54/-31.73, respectively. Both DPD-2224 and 2234 retained negative surface charges yet at absolute values less than that of their parental strain. No significant difference between the two growth periods was observed, nor was at environmental pH of 6, 7, and 8. The MATH experiments showed minimum degrees of hydrophobicity in all three strains, indicating that a mechanism stronger than adsorption (van der Waal force or hydrogen bond) is needed, such as positively charged crosslinking agents. This study establishes the selection criteria of potential cell immobilization mechanisms, which are crucial for biosensor development.
Session 15A, Biotechnology
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