Specificity, induction, and absorption of pesticin

Abstract

Irradiation of pesticinogenic (Pst(+)) cells of Yersinia pestis with ultraviolet light resulted in a five- to eightfold increase in titer of intracellular pesticin. Extracellular activity in irradiated or control cultures never approached that found within the bacteria. Upon chromatography of crude extracts of Pst(+) cells on columns of diethylaminoethyl-cellulose, Sephadex G200, and calcium hydroxyapatite, fractions were recovered which inhibited the growth of indicator cells of Escherichia coli, Y. pseudotuberculosis, Y. enterocolitica, and Pst(-)Y. pestis. By means of these methods, in conjuntion with fractional precipitation with ammonium sulfate, the antibacterial activity was purified to homogeneity (as judged by disc gel electrophoresis and analysis by double diffusion in agar). The relative sensitivity of each cell type was constant and not affected by the state of purification. These findings indicate that the pesticin molecule alone accounts for lethality. Cells of E. coli and Y. pseudotuberculosis were about 100 and 10 times more sensitive to pesticin, respectively, than were those of Pst(-)Y. pestis. Activity directed against sensitive cells of these three species was enhanced by 0.1% ethylenediaminetetraacetate (EDTA) and completely inhibited by 0.01 m hemin or 0.001 m Fe(3+). The response of Y. enterocolitica to pesticin was variable in the presence of EDTA and was not influenced by Fe(3+). Attempts to detect common surface structures responsible for absorption of pesticin by the four cell types were not successful.