Cobalt and bacterial growth, with special reference to Proteus vulgaris.

For the past five years we have been engaged in an investigation of the effect of cobalt on the growth and metabolism of bacteria, especially of Proteus vulgaris. The emphasis on Proteus followed requests for aid in the control of growth of this penicillinand sulfa-resistant organism in cases of peritonitis, cystitis, and eye infections. Interest in cobalt as a growth inhibitor of microorganisms has been extremely limited. Such studies as have been made deal primarily with the concentrations of the metal necessary to kill the cells of bacteria, yeast, or paramecia after a given period of exposure (Bokorny, 1905, 1913; Krauss and Collier, 1931; Johnson, Carver, and Harryman, 1942). Apart from observations on the therapeutic use of cobalt in the treatment of tuberculosis (Renon, 1915; Rondoni, 1920; Mascherpa, 1929), no attempt, so far as we are aware, has been made to study in detail the nature of the action of cobalt on bacteria. In this paper we shall consider only those aspects of the growth-inhibitory effect of cobalt on bacteria, particularly P. vulgaris, which are of a cultural rather than of a metabolic nature. The results of our metabolic studies will appear subsequently.