Emulsan in <i>Acinetobacter calcoaceticus</i> RAG-1: Distribution of Cell-Free and Cell-Associated Cross-Reacting Material

Abstract

Emulsan is an extracellular polymeric bioemulsifier produced by Acinetobacter calcoaceticus RAG-1. Antibodies prepared against purified emulsan inhibited the activity of the polymer in a standard emulsification test. These antibodies were used to develop a sensitive enzyme-linked immunosorbent assay to monitor changes in cell-free emulsan throughout the growth cycle. This assay was also used to detect emulsan associated with the cell surface and to monitor changes in the distribution of cell-free and cell-associated emulsan throughout the growth cycle. Cells in the early exponential phase exhibited relatively large amounts of cell-associated emulsan which decreased rapidly between the midexponential and early stationary phases. This drop in cell-associated material was accompanied by a rise in the concentration of extracellular polymer. Moreover, in agreement with previous results (C. Rubinovitz, D. L. Gutnick, and E. Rosenberg, manuscript in press), production of cell-free emulsan was enhanced in the presence of chloramphenicol. The release of this material from the cell surface in the presence of chloramphenicol apparently involved the synthesis of cell-associated cross-reacting material since the relative amount of such cell-bound polymer remained constant during the treatment with the drug.