Physiological and morphological effects of phenethyl alcohol upon a gram-negative marine pseudomonad.

Abstract

Phenethyl alcohol (PEA) at 0.15% (v/v) inhibited the growth of a gram-negative marine pseudomonad. After removal of the alcohol, the cells remained viable even when pre-exposed to PEA concentrations as high as 0.25% (v/v). Phenethyl alcohol inhibited uptake of α-aminoisobutyric acid (AIB) and also prevented amino acid exchange. At PEA concentrations of 0.25% or less, inhibition of AIB uptake was completely reversible and, provided K+ was added to the uptake medium, the treated cells could accumulate AIB to the same extent as control cells. If K+ was omitted from the medium, the capacity of the cells to accumulate AIB was found to be proportional to the length of time that the cells had been exposed to the alcohol. Phenethyl alcohol caused a rapid efflux of intracellular K+ and AIB-14C from previously loaded cells, and such cells were noticeably smaller than normal cells and had a plasmolyzed or irregular outline when observed by phase contrast. Thin section electron microscopy, and freeze-etch studies, showed that the plasmolyzed appearance of these cells was due to local invagination of the cytoplasmic membrane. After removal of the alcohol, the subsequent addition of K+ to the incubation medium caused the cells to become deplasmolyzed. It seems likely that the inhibition of cell growth by PEA is due to two major causes: (1) direct interference of the compound with the normal physiological functions of the cytoplasmic membrane and, (2) PEA induced structural changes occurring within the cell envelope.