The effects of hypochlorite on bacterial capsular material

Abstract

The uptake of chlorine by mixed bacterial cultures of varying polysaccharide content was studied in a homogeneous reaction system. The destructive effects of hypochlorite oxidation were noted by measuring decreases in solids concentrations of bacterial cultures and by measuring changes in molecular size distributions of polysaccharides extracted from those cultures. The bactericidal effects of a given concentration of chlorine were observed for bacteria with and bacteria without polysaccharide capsules. The uptake of chlorine by bacterial cultures was found to be significantly faster and greater for cultures grown at a higher carbon-to-nitrogen ratios (larger production of polysaccharides) as opposed to cultures grown at a lower carbon-to-nitrogen ratios, (smaller production of polysaccharides) . Greater destruction of solids occurred in bacterial cultures with a higher polysaccharide-to-totalsolids-ratio for equal chlorine concentration applied. The molecular size distribution of bacterial polysaccharide molecules was shifted to a smaller average molecular size by the hypochlorite oxidation reactions. At the chlorine concentration used (50 mg/1), no added bactericidal protection was observed in bacteria with larger capsules.