Stability of solvent production by Clostridium acetobutylicum in continuous culture: strain differences

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Abstract
Woolley, R.C. & Morris, J.G. 1990. Stability of solvent production by Clostridium acetobutylicum in continuous culture: strain differences. Journal of Applied Bacteriology69, 718–728.Several strains of Clostridium acetobutylicum, including strains ATCC 824 and DSM 1731, continue to produce solvents during prolonged periods of chemostat culture. In such cultures, dominance is established by asporogenous mutant(s) that retain the ability to produce solvents. Strain NCIB 8052 (which is not identical with ATCC 824) behaved differently in that its chemostat cultures invariably became acidogenic due to ultimate selection of asporogenous mutant(s) unable to produce solvents, incapable of synthesizing granulose, and demonstrating enhanced sensitivity to environmental stresses of various types. These mutants spontaneously reverted, at a low but measurable frequency, to the parental phenotype, indicating thai their multiple loss of capacities was the pleiotropic consequence of a lesion in some global regulatory gene. Their resemblance to previously described cls mutants of strain P262 and the possible nature of the affected regulatory gene are discussed. A simple tetrazolium blue plate assay procedure is described which allows visual discrimination between solvent‐producing and non‐solventogenic colonies of Cl. ocetobutylicum.