Effect of saline on the releasability of alkaline phosphatase from cells of Serratia marcescens.

The effect of 0.9% sodium chloride solution on the release of alkaline phosphatases from cells of four strains of Serratia marcescens was studied. Saline had a greater action in the releasability of the enzyme on cells of the polymyxin B sensitive strains than those of the polymyxin B resistant strains. SDS-polyacrylamide gel electrophoresis of the released materials showed the presence of proteins and lipopolysaccharide components of the outer membrane as well as enzyme activity in all four strains. Cells from strains harvested under higher temperatures contained more releasable activity in the salin wash fraction than those harvested under refrigerated condition. Active components with molecular weights of 190,000 and 110,000 daltons were either absent or present to a lesser degree in the extracts released by the polymyxin B treatment of the washed cells. However, active components not released by saline were found in the polymyxin B extracts. Contrary to other reports, results of this study clearly showed the ubiquitous nature of alkaline phosphatase in S. marcescens. It appears that their releasability is related to the polymyxin B susceptibility as well as the instability of the outer membrane of the cell envelope.