The Inhibitory Effect of Lipase on Bacterial Growth in Media Containing Fatty Acid Esters

Abstract

It has been reported from this laboratory that serum albumin is essential for the initiation of growth by small inocula of tubercle bacilli in a liquid medium containing "tween 80"2 which promotes submerged growth of these orgtmsms (Dubos, 1945; Dubos and Davis, 1946). The albumin acts as a protective rather than a nutritive growth factor, binding traces of unesterified fatty acid which inhibit growth of small inocula (Davis and Dubos, 1947). The commercial bovine serum albumin, however, also makes the medium somewhat unstable, which is particularly important because tubercle bacilli grow so slowly. Inocula containing only small numbers of bacilli (ca. 10 to 20) require a period of cultivation of 2 weeks to attain visible growth, yet after sterile incubation of the tween-albumin medium at 37 C for 2 weeks, it was unable to support growth of even large inocula. It appeared possible that in the race between bacterial multiplication and spontaneous deterioration of the medium even smaller inocula might be prevented from surviving. This prediction could be confirmed after the deterioration was traced to hydrolysis of tween 80 by