The growth behavior of Gram-negative bacteria when exposed to high concentrations (50% v/v) of water-insoluble organic solvents was investigated. The solvents were chosen according to their polarity values as denoted by a logarithmically expressed parameter log P, where P is the partition coefficient of a given solvent in an equimolar mixture of octanol and water. The cell growth was measured by the number of colonies developed on a solid agar medium in direct contact with the solvents. All 31 strains tested showed characteristic growth patterns. The survival and subsequent growth of bacteria increased with the increase in the log P value and was found to be strain specific. For all the strains, 100% cell growth was reached from 0% within 0.1-0.4 log P units. Log P50 values, defined as the log P values at which 50% of the cells form colonies, were determined for each bacterial strain. On the whole, Pseudomonas strains were found to be more resistant to apolar solvents than all other bacteria tested. This resistance was dependent not only on the polarities but also on the toxic nature of different organic solvents, the cell membrane components, and to a limited extent, the growth medium. A tenfold increase in the Mg2+ concentration in the growth medium enhanced the solvent resistance of E. coli but had no such effect on Pseudomonads. In general, different growth temperatures had no impact on the solvent resistance of the Gram-negative bacteria tested.
Bibliographical noteFunding Information:
I would like to thank Prof. P. A. Williams for the gift of P. putida strain mt-2; Dr. D. B. Janssen, Prof. P. J. M. van Haastert, Dr. L. A. Huisman, and Dr. H. J. P. Marvin for providing the strains used in this study; and Dr. H. Preusting for critically reading this manuscript.T he major part of the work described in this paper was performed at the Department of Biochemistry, University of Groningen, The Netherlands. I am deeply indebted to Prof. B. Witholt for his invaluable support and encouragementd uring the course of this work. I gratefully acknowledge the fellowship granted by the Netherlands Universities Foundation For Intema-tional Cooperation (NUFFIC).
Copyright 2004 Elsevier Science B.V., Amsterdam. All rights reserved.
- Log P
- Solvent resistance
- Two-phase systems