DODECYLGUANIDINE MONOACETATE (DODINE) CAUSES SEVERE MEMBRANE DAMAGE IN PSEUDOMONAS-SYRINGAE ABOVE THE CRITICAL MICELLE CONCENTRATION

The release of K+ from Pseudomonas syringae cells treated with dodecyl guanidine monoacetate (dodine) was followed with a K+-selective glass electrode. Treatment of the cells with 5 - 15 mumol/l dodine resulted in low levels of K+ release, but higher surfactant concentrations caus ed extensive and rapid K+ efflux. Dodine concentrations that caused hi gh K+ release also induced significant leakage of inorganic phosphate. The addition of 5 - 10 mumol/l dodine also caused an increase in the rate of oxygen consumption in the presence of glycerol or succinate, b ut an increase in concentration from 10 to 40 mumol/l resulted in a co ncomitant decrease in O2 consumption. The results from this and previo us work suggest that dodine inhibits respiration firstly by causing dr ainage of coenzymes, and then by a direct interaction with the compone nts of the respiratory chain. Previous work showed that above 25 mumol /l, dodine molecules aggregate to form micelles. The results therefore suggests that, in contrast with other cationic amphiphiles, the micel lar form of dodine is more damaging to the cytoplasmic membrane than t he free molecules.