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Physiology and Biochemistry

Effects of Pseudomonas syringae Phytotoxin, Syringomycin, on Plasma Membrane Functions of Rhodotorula pilimanae. Lei Zhang, Graduate Student, Department of Chemistry and Biochemistry, Utah State University, Logan 84322-0300; Jon Y. Takemoto, Professor, Department of Biology, Utah State University, Logan 84322-0300. Phytopathology 77:297-303. Accepted for publication 6 May 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-297.

The effects of purified syringomycin on whole cells and a plasma membrane-enriched fraction of the yeast Rhodotorula pilimanae were investigated. Syringomycin at concentrations between 0.25 and 3.0 ?g/ml inhibited growth and stimulated the cellular uptake of oxygen, tetraphenylphosphonium (TPP) cations, and dimethyloxazolidinedione (DMO). The effects of TPP and DMO uptake were reversed by energy uncouplers and anaerobiosis and were unaffected by KCl. Syringomycin at 25 ?g/ml stimulated the activity of the plasma membrane-associated ATPase. Results indicate that syringomycin inhibits cell growth by altering the electrical potential and pH difference across the plasma membrane and stimulation of the proton-pumping ATPase.