Perméation du glycérol et sporulation chez Bacillus subtilis

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Abstract
Glycerol permeation was studied in B. subtilis 168 trp− gl+ and its two mutants gl−1 and gl−2. The mutant gl−1 has all the enzymes required for the degradation of endocellular glycerol. The mutant gl−2 is impaired in the enzyme glycerol kinase. In the presence of increasing concentrations of glycerol-14C, incorporation of radioactivity by the wild strain obeys Michaelis law while it is linear in the case of the mutant gl−1. Thus the mutant gl−1 is cryptic towards glycerol. No evidence was found as to the formation of an intracellular pool of glycerol in any of the three strains (gl+, gl−1, gl−2) studied. This result suggests that permeation of glycerol in B. subtilis is probably facilitated by diffusion. Sporulation of the mutant gl−1 in presence of glycerol is explained by a mutation affecting the permeation system. Thus glycerol enters in the mutant cells by simple diffusion. As a consequence, the metabolism is greatly reduced and the sporulation mechanism is triggered.

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