Mode of action of a bacteriocin from Erwinia carotovora III. properties of phospholipase a of erwinia carotovora and its involvement in phospholipid degradation caused by carotovoricin.

Abstract

Phospholipase A in the outer membrane of E. carotovora 645ArT was activated by various detergents such as cholate, deoxycholate and Triton X-100 and methanol. The enzyme was inhibited by EDTA, and Ca2+ was required for the enzyme activity. The enzyme hydrolyzed phosphatidylethanolamine and phosphatidylglycerol to form nearly equimolar amounts of free fatty acids and lysophospholipids. Cardiolipin was not susceptible to the enzyme. In a mutant strain deficient in phospholipase A activity, the rate of degradation of membrane phospholipid caused by carotovoricin Er, a bacteriocin from E. carotovora strain Er, declined to about 1/10 of that of the parent strain under similar conditions. Lysis caused by carotovoricin Er also diminished in the phospholipase A-deficient mutant. Carotovoricin Er apparently provokes an activation of phospholipase A in sensitive cells, and subsequently, degradation of membrane phospholipid and cell lysis result. Phospholipase A-deficient mutants retained sensitivity to killing activity of carotovoricin Er. Activation of phospholipase A may not be related to the primary bactericidal action of the bacteriocin.