Characterization of cellulose, an extracellular polysaccharide produced by shiga toxin producing Escherichia coli
Yoo, Byong Kwon
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Shiga toxin producing Escherichia coli (STEC) are known to have several defense mechanisms, one of which is the production of protective, extracellular substances such as the production of cellulose, a long-chain polysaccharide of glucose with β-1, 4 glycosidic bonds. This study was undertaken to determine the physiological conditions favoring the production of cellulose and to prepare pairs of STEC strains, comprising of a cellulose producing parent and a spontaneous cellulose deficient mutant, useful for research studies designed to address the roles of cellulose in protecting the cell of STEC under stress. It was found that the cultural conditions that favored the production of cellulose by STEC included a 28oC incubation temperature, aerobic atmosphere and presence of 2% of ethanol on Luria Bertani no salt agar with a pH value of 6.0 and a water activity of 0.99. Two pairs of STEC strains were prepared and characterized. The two members within each pair shared the same serotypes and similar PFGE profiles. Profound morphological differences were however, found between the two types of cells. The two members of each STEC pair shared similar growth characteristics except under extreme stress in the phenotypic microarray study. All these STEC strains were subjected to oxidative (10, 20 and 30 mM H2O2), osmotic (1, 2 and 3 M NaCl) and acidic (pH 3.0, 3.5 and 4.5) stress as well as chlorine treatment (25, 50 and 100 µg/ml NaOCl). Cells of cellulose producing strains were found to be relatively more resistant than those of the cellulose deficient strains.