Resistance to chlorine of freshwater bacterial strains.

The disinfectant properties of chlorine have been known for centuries but in the last few years water chlorination has attracted some criticism due to its secondary effects and the increased resistance of bacterial strains to chlorine inactivation. In this paper the kinetics of inactivation by chlorine of different Gram-positive and Gram-negative bacterial strains isolated from chlorinated water is studied. The Gram-positive strains were more resistant to chlorine and the behaviour of some of them in the presence of chloramphenicol suggests either the synthesis of unique proteins or aggregation of the bacteria as mechanisms of resistance to inactivation. The concept of Ki, the inactivation rate constant, by comparison with Ks in Michaelis-Menten enzyme kinetics (considering enzymic saturation), or with Ks in Monod growth kinetics (considering limiting rates of transport and metabolism of substrates), may be an interesting parameter to define microbial resistance to disinfectants and toxics.