TOXICITY OF HOMOLOGOUS SERIES OF ORGANIC-SOLVENTS FOR THE GRAM-POSITIVE BACTERIA ARTHROBACTER AND NOCARDIA SP AND THE GRAM-NEGATIVE BACTERIA ACINETOBACTER AND PSEUDOMONAS SP

The toxicity of homologous series of organic solvents has been investi gated for the gram-positive bacteria, Arthrobacter sp. and Nocardia sp ., and the gram-negative bacteria, Acinetobacter sp. and Pseudomonas s p. The hydrophobicity of the solvent, expressed by its logP(octanol), proves to be a good measure for the toxicity of solvents in a two-phas e system. The transition from toxic to nontoxic solvents occurs betwee n logP(octanol) 3 and 5 and depends on the homologous series. No corre lation has been found between the hydrophobicity of the substituent on the alkyl backbone of the solvent and the location of the transition point in toxicity. The logP(octanol), above which all solvents are non toxic, is used to express the solvent tolerance of the bacteria. In ge neral, the solvent tolerance of gram-negative bacteria is found to be slightly higher than that of gram-positive bacteria, but this does not hold for all homologous series of organic solvents investigated. Beca use the toxicity effects of organic solvents in a two-phase system can be ascribed to molecular as well as phase toxicity effects, molecular toxicity effects were investigated separately in a one-phase system w ith subsaturating amounts of organic solvent. The solvent concentratio n in the aqueous phase, at which 50% of the metabolic activity of the bacteria is lost, is used to express solvent toxicity. This concentrat ion is found to be similar for the gram-positive Arthrobacter and the gram-negative Acinetobacter. Assuming the critical membrane concentrat ion theory (S.J. Osborne et al. Enzyme Microb. Technol. 1990, 12: 281- 291) to be valid, it can be concluded that differences in solvent tole rance between these two bacteria, cannot be ascribed to differences in response to molecular toxicity. Prediction of the toxicity of any sol vent, using the critical membrane theory, appears to be possible in th e case of alkanols or alkyl acetates. However, prediction of the toxic ity of ethers appears to be impossible. (C) 1993 John Wiley & Sons, In c.