Abstract
The effect of methanol, ethanol, acetone, N,N-dimethylformamide (DMF), dimethyl sulfoxide and Nujol on the growth of Escherichia coli DH5α, Bacillus subtilis and Saccharomyces cerevisiae D273 was investigated. All of the tested cultures appeared susceptible to the organic media they were treated with, which evinced in apparent hindering of cell development. The observed diverse solvent tolerance, except from their different biochemical activity, may also be related to the changes in cell membrane fluidity induced by the solvent species. Parallel electron paramagnetic resonance investigations using egg yolk lecithin model liposomes revealed that the fluidity of the phospholipid system in cell membranes may either be considerably decreased (Nujol, DMF, ethanol) or increased (acetone), thus rendering difficult the intracellular nutrient supply. Hence, even the chemically neutral Nujol produced a distinct cell-growth inhibitory effect. These results are fairly consistent with the outcome of the survival tests, particularly for the bacteria strains.
Highlights
IntroductionOrganic solvents, such as dimethyl sulfoxide (DMSO), N,NDimethylformamide (DMF) or alcohols are frequently used in deactivation of microorganisms [1,2,3,4,5,6,7]
Keywords Organic solvents · Bacteria · Yeast · Liposomes · Electron paramagnetic resonance (EPR). Organic solvents, such as dimethyl sulfoxide (DMSO), N,NDimethylformamide (DMF) or alcohols are frequently used in deactivation of microorganisms [1,2,3,4,5,6,7]
Two effects are important here, a chemical one, which follows from the biochemical activity of solvent species, and a physical one resulting from the non-chemical intermolecular interactions involving the cell membrane system and solvent molecules
Summary
Organic solvents, such as dimethyl sulfoxide (DMSO), N,NDimethylformamide (DMF) or alcohols are frequently used in deactivation of microorganisms [1,2,3,4,5,6,7] They usually serve as a liquid medium when introducing a specified dopant (drug), they may themself prove toxic for a number of bacteria or fungi. Samples (0.1 ml) were taken periodically and plated on a solid medium, and the number of living cells in the culture was determined by the viable count method [37, 38] In this work it was assessed for the solvent concentration of 4.8% v/v, at which practically all of the tested microorganisms were still able to grow. In the discussion of results, normalized (relative) values F/F0 and τ/τo have been used (F0 and τo apply to the reference liposome sample containing no extra solvent)
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