Transduction of chromosomal genes between enteric bacteria by bacteriophage P1.

We have used P1 transduction to create intergeneric hybrid strains of enteric bacteria by moving the genA and hut genes between Klebsiella aerogenes, Escherichia coli and Salmonella typhimurium. The use of E. coli as the recipient in such transductions permits the construction of episomes and specialized transducing phage containing non-E. coli material. The effect of host restriction modification and deoxyribonucleic acid homology on the frequency of intergeneric transduction of these loci has been examined.     

Comparison of radioimmunoassay and gas-liquid chromatography analyses of progesterone concentrations in cow's milk.

Progesterone concentrations in milk were not significantly different when quantitated by different methods (RIA vs. GLC). There was a significant day effect (P less than 0.05) on milk progesterone level due apparently to gradually decreasing values as pregnancy advanced over days 30, 120 and 210. The means for the percent fat content were different (P less than 0.05) for all comparisons among four times of collection (immediately premilking, milking pool, immediately postmilking, and 3 hr postmilking). For progesterone concentration, the main effect of time and the three-way interaction (time times antiserum times purification method) were significant (P less than 0.005); all other main effects and interactions were not significant. Within each of 4 assay groups (2 antisera times 2 purifications), the concentration of progesterone was greater (P less than 0.05) for the samples which were collected immediately postmilking than for any of the other times of collection. The three-way interaction seemed due primarily to difference in progesterone determinations among the four assay groups in the samples which were taken immediately postmilking. Over all milk samples within each assay group, the percent fat content and the concentration of progesterone were positively correlated (r = 0.71, P less than 0.01).     

Localization of kallikrein in the guinea-pig submandibular gland

The localization of kallikrein in the acinar and the ductal components of the guinea-pig submandibular gland was investigated by a microdissection technique and an esterase assay. The results indicated that a major portion of the kallikrein is located in the striated duct cells. These results disagree with previous studies in the guinea-pig but are consistent with findings in the rat and cat submandibular gland.     

Genetic analysis of succinate utilization in enzyme I mutants of the phosphoenolpyruvate: sugar phosphotransferase system in Escherichia coli.

Studies on the reversion characteristics of Escherichia coli strains carrying various mutations in the pts region have led to the recognition of a mutation, suc-1, with a previously undescribed phenotype. Strains carrying the suc-1 mutation grow normally on most sources of carbon but are unable to utilize succinate effectively. The suc-1 mutation can be separated genetically from the tightly linked ptsI6 mutation. Reversion of suc-1 mutants for growth on succinate yields interesting classes of suppressor mutations.