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E M JOHNSON

Publications and source records attributed to E M JOHNSON.

12 recordsLinked to original sources
PubMed1965

GENETIC MAPPING OF VI AND SOMATIC ANTIGENIC DETERMINANTS IN SALMONELLA.

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Barbara Krauskopf, and L. S. Baron. Genetic mapping of Vi and somatic antigenic determinants in Salmonella. J. Bacteriol. 90:302-308. 1965.-The Vi antigen and somatic antigen 9 were transferred to Salmonella typhimurium recipients by mating with S. typhosa Hfr TD-7, and the genetic determinants of these antigens were located. A gene responsible for Vi antigen expression, ViB was found to be associated with the inlpurA-pyrB linkage group, and the order ViB-inl-purA-pyrB was established. The determinant of somatic antigen 9 was found closely linked to the his gene, and cotransduction of these determinants was accomplished with phage PLT-22. Moreover, all conjugation and transduction hybrids which received the somatic antigen 9 determinant concurrently lost somatic antigen 4. Similarly, S. typhosa hybrids produced by transfer of his and the gene for somatic antigen 4 from S. typhimurium Hfr B2, or by cotransduction of these genes with PLT-22, also lost somatic antigen 9. These results indicated that the genetic determinants of the somatic antigen 9 and 4 are probably allelic. A second Vi antigen determinant, ViA, located near his, was discovered in matings of S. typhimurium Hfr B2 with a Vi-negative S. typhosa recipient. Vi-positive S. typhosa hybrids were obtained from this cross in which neither parent expressed the Vi antigen, indicating that this Vi determinant of S. typhosa is present also in S. typhimurium.

Agglutination↗
PubMed1964

RECIPIENT ABILITY OF SALMONELLA TYPHOSA IN GENETIC CROSSES WITH ESCHERICHIA COLI.

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Stanley Falkow, and L. S. Baron. Recipient ability of Salmonella typhosa in genetic crosses with Escherichia coli. J. Bacteriol. 87:54-60. 1964.-Salmonella typhosa strain 643WS(r) was mated with Escherichia coli Hfr strains W1895 and Hayes, with single marker selection for the E. coli genes lac(+) (lactose utilization) and ara(+) (arabinose utilization). Four classes of Salmonella hybrids were obtained, each class possessing one marker derived from one E. coli parent. In a series of eight genetic crosses, in which each hybrid class was remated with each of the Hfr strains, recipient ability of the hybrids was increased only when their substituted E. coli genetic section matched the lead region of the Hfr chromosome. Data obtained from replica plating indicated that the S. typhosa 643WS(r) population is probably homogeneous with respect to its initial ability to mate with E. coli. Transfer of the F-lac element was found to occur only slightly less efficiently from an E. coli F' donor to S. typhosa than it did to an E. coli F(-) strain. This indicated that E. coli is able to conjugate almost as effectively with S. typhosa as it does intraspecifically. However, failure to detect beta-galactosidase production by merozygotes derived from an E. coli Hfr W1895 x S. typhosa mating indicated that transfer of chromosomal lac(+) may be impaired.

Arabinose↗
PubMed1964

CHROMOSOME TRANSFER KINETICS OF SALMONELLA HFR STRAINS.

Johnson, E. M. (Walter Reed Army Institute of Research, Washington, D.C.), Stanley Falkow, and L. S. Baron. Chromosome transfer kinetics of Salmonella Hfr strains. J. Bacteriol. 88:395-400. 1964.-The kinetics of chromosome transfer of an Hfr strain of Salmonella typhosa and an Hfr strain of S. typhimurium were examined in interrupted matings with multiply auxotrophic S. typhimurium recipients. The S. typhosa Hfr, TD-7, was found to transfer the pro-A, met-A, arg (A, C, F, or H), and ile markers at 8, 32, 36, and 51 min, respectively, after contact with the recipient strain. Comparison of these entry times with those of the analogous Escherichia coli Hfr P4X-6 for the same markers showed the gene order to be identical. However, the TD-7 entry times were considerably extended over those of P4X-6, which transfers these markers of E. coli F(-) strains at, respectively, 5, 20, 22.5, and 28 min. A similar extension of the entry times was noted with the S. typhimurium Hfr, SR-305, which transfers the markers in the reverse order, ile-met-A-pro-A, at 3 to 4, 18, and 46 min, respectively. Examination of P4X-6/Salmonella Hfr entry time ratios showed them to be constant at 0.63 for the earlier markers transferred by both TD-7 and SR-305. These data suggest that the physical length of the Salmonella chromosome is the same as that of E. coli, and that the rate of chromosome transfer of the Salmonella Hfr strains to S. typhimurium recipients is only 0.63 that of P4X-6 to E. coli F(-) strains under the same physical conditions.

Amino Acids↗