Capillary electrophoresis of Escherichia coli: a first attempt

In the last few years, capillary electrophoresis have been used to characterize and separate microorganisms on the bases of their electrophoretic mobility [1]. Indeed microorganisms have an external structure, the “cell wall”, with a characteristic molecular composition which distinguishes microbial species and strains from each other (yeasts, bacteria, viruses). More importantly, the cell wall contains several ionizable groups that in particular conditions give rise to a superficial charge causing them to migrate with a typical migration time under an applied electric field [2,3]. Our previous works on backer’s yeast [4] have demonstrated that the characteristic electropherogram of this species shows two peaks ascribed to neutral and negative charged cells. Relevant microscopic studies have further pointed out that the electrophoretic profile also reflects the dimensional distribution of cells in the analyzed sample. In the following work, our interest has been focused on the electrophoretic behavior of Escherichia coli, a microorganism of significant interest for its role in several infectious diseases and its importance in biotechnological industries. As a first attempt, it was necessary to optimize the electrophoretic conditions for the identification and efficient separation of this microorganism by capillary electrophoresis; accordingly, the effects of the running buffer, pH, the separation voltage and the microbial aggregation on the electrophoretic profile of Escherichia coli were studied. Once typical electropherogram of that bacteria was identified, a sample containing Saccharomyces cerevisiae and Escherichia coli was analyzed using capillary electrophoresis and the experimental results have demonstrated the power of the technique in detecting the bacterial contamination of fungal sample. Thus capillary electrophoresis is able to replace traditional method of microbial identification because it permits rapid, easy and highly sensitive microbial analysis and diagnoses at low costs on several biological samples. [1] E.Kłodzińska, B.Buszewski, Analytical Chemistry, 81, 2009, 8-15. [2] A.T.Poortinga, R.Bos, W.Norde, H.J.Busscher, Surface Science Report. 47, 2002, 1-32. [3] S.P.Radko, A.Chrambach, Electrophoresis, 23, 2002, 1957-1972. [4] F.Crispo, A.Capece, R.Ciriello, P.Romano, A.Guerrieri, paper under submission.