Tris- and deoxycholate-induced lysis in colistin-treated Proteus strains

Strains of Proteus spp. were pretreated with colistin (polymyxin E) and resuspended in either Tris buffer or sodium deoxycholate. Leakage of potassium and materials with an absorption maxima at 260 nm increased on resuspension of two pretreated Proteus mirabilis strains in Tris buffer or sodium deoxycholate. The activity of Tris increased up to pH 9 and of sodium deoxycholate up to 1,000 micrograms/ml. Greater leakage occurred with resuspension in Tris buffer than in sodium deoxycholate. Other Proteus strains tested did not produce leakage following similar treatment.