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Abstract
Clostridium pasteurianum forms acetic and butyric acids in an initial growth phase, which is a typical feature of clostridial acetone-butanol fermentation where an initial accumulation of acids is followed by production of solvents 1-butanol, acetone and ethanol. The initiation of the solvent production coupled with endospore formation leads to decrease of cell-wall thickness; thinner cell wall is more resistant against solvents and dyes. These changes can be observed by the method based on adaptation of Gram staining. The cell wall of G^sup +^ bacteria allows the entry of hexidium iodide and rhodamine 123, whereas the outer membrane of G^sup -^ bacteria does not allow the uptake and therefore G^sup +^ bacteria are stained with higher fluorescence intensity than G^sup -^ bacteria. The ratio of fluorescence intensity (FI) to forward scatter (FSC) was determined to correspond to G^sup +^ bacteria when clostridia were producing less solvents. The significant drop of the ratio FI to FSC to the level corresponding to G^sup -^ bacteria is detected after initiation of solvent production.[PUBLICATION ABSTRACT]