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Characterization of enterobacteria by starch-gel electrophoresis of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase.

Specific activities and electrophoretic mobilities of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase were determined in 38 isolates of the family Enterobacteriaceae and in 10 isolates of the related Pasteurella. The deficiency of glucose-6-phosphate dehydrogenase in P. pestis was verified. Enzymes obtained from different strains of the same species exhibited an unexpected degree of heterogeneity. For example, 8 and 11 apparent variants of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase, respectively, were found in 14 strains of Escherichia coli. Although similar frequencies of heterogeneity were noted in 7 strains of P. pseudotuberculosis, 5 species of Shigella, and 8 species of Salmonella, differences in mobility were generally small in comparison with those observed between strains of E. coli. Values obtained for the pasteurellae, shigellae, and salmonellae, thus fell within narrow ranges that may prove typical for the genera. However, most of these ranges, as well as many values observed for single species of other genera, were overlapped by the wide range recorded for E. coli. The significance of this observation was discussed with respect to the relative age and taxonomic position of the organisms in question. The method could be used to distinguish between most wild-type strains of the same species and should thus facilitate investigations of genetic transfer and epidemiology.

Electrophoresis↗

Growth of male-specific bacteriophage in Pasteurella harboring F-genotes derived from Escherichia coli.

When either the F' lac or the F'Cm plasmid was transferred from Escherichia coli into Pasteurella pseudotuberculosis, the P. pseudotuberculosis (F') strains isolated formed plaques with both ribonucleic acid (RNA)-containing and deoxyribonucleic acid-containing male-specific phages. In contrast, strains of P. pestis harboring E. coli (F') plasmids did not form plaques with male-specific phages, although such strains permitted limited multiplication of phage MS2. The adsorption and burst size of MS2 were approximately the same in both species of Pasteurella, but the per cent of adsorbed MS2 that produced infective centers was much lower in P. pestis than it was in P. pseudotuberculosis. By use of a sib-selection technique of P. pestis (F') cells, we isolated a single clone that could form MS2 plaques. (32)P-labeled MS2 adsorbed equally to and its RNA penetrated equally into both the typical MS2-nonpermissive P. pestis cells and the MS2-permissive P. pestis cells. No host modification occurred after growth of MS2 in Pasteurella. Our data suggest that typical strains of P. pestis inhibit the intracellular development of phage MS2.

Adsorption↗

Mode of action of pesticin.

The mode of action of pesticin, a bacteriocin produced by many strains of Pasturella pestis, was studied. Pesticin action on macromolecular synthesis of a sensitive strain of Escherichia coli, strain phi, was found to have features similar to those of colicin E2-317 acting on the same strain. After exposure to pesticin, deoxyribonucleic acid synthesis was arrested and ribonucleic acid was degraded, but little effect was observed on protein synthesis. Pesticin, like colicin E2-317, induced lysogenic E. coli phi (P1), but, unlike the colicin, was active in the presence of dinitrophenol. Trypsin was found to reverse pesticin action up to 15 min after its addition at 40 C to E. coli phi. Pesticin action was studied on three sensitive bacterial strains, P. pestis 2C, P. pseudotuberculosis, and E. coli strain phi, which vary widely in their optimal growth temperature. P. pestis grows best at 29 C, P. pseudotuberculosis at 37 C, and E. coli phi at 40 C. It was found that pesticin action on all three strains was optimal at 40 C. Whereas the titer of pesticin was the same on all three strains when determined on agar, E. coli phi was the most sensitive to pesticin action in broth. No action of pesticin in broth on P. pseudotuberculosis was observed unless Ca ions were added. The effect was not immediate; that is, the cells had to be grown in a medium containing Ca(++) before they displayed sensitivity to pesticin.

Bacterial Proteins↗

Specificity, induction, and absorption of pesticin.

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.

Absorption↗