LYSIS OF CELL WALLS AND INTACT CELLS OF PSEUDOMONAS AERUGINOSA BY ETHYLENEDIAMINE TETRAACETIC ACID AND BY LYSOZYME

Abstract

It was shown that Pseudomonas aeruginosa strain 64 was extensively Iysed by EDTA alone and that destruction of cells was as complete as when lysozyme was used in combination with EDTA as evidenced by microscopic examinations and viability tests of the bacterial suspensions. Lysozyme alone caused no appreciable lysis. Lysozyme was not completely without effect. Cells that were preincubated with lysozyme, washed, and resuspended in the presence of EDTA lysed at the same rate and to the same extent as in a system containing both EDTA and lysozyme. Electron microscopy revealed that, after incubation with lysozyme, cells showed altered physical appearances manifested by "ballooning" and bulging of the cell walls. Incubation of cells with rhodamine-labelled lysozyme indicated that lysozyme is bound to the cellular surface and that it is readily removed by washing.There is evidence that EDTA acts through its chelation properties. Calcium was chelated in greatest quantity. EDTA was replaceable by structurally related polyacetic acid chelating agents but not by other chelating agents or by detergents. It is concluded that the binding of divalent metals, which may function to form cross-linkages, is essential for the integrity of the cell walls of P. aeruginosa.