The virulence of Pasteurella multocida strains in experimental infections of mice has been shown to depend on the iron contents of the cultivation media. Frequent passages of bacteria on iron-deficient growth media result in drastic decrease of virulence. In the case of one strain also immunogenicity was lowered. The results with nutritional media differing in their iron contents show that iron probably exhibits a regulatory effect on the production of a not yet identified virulence.
In a methodical paper two analytical‐chemical procedures are described which concern the control of L‐lysine formation during fermentation processes. On one hand lysine is determined fluorimetrically with o‐phthalaldehyde at defined pH, on the other spectrophotometrically with ninhydrine in acidic medium. The analytical conditions are discussed with respect to specifity, interferences, accuracy and reproducibility. A comparison of values with Autoanalyzer technique and two other methods for lysine determination offers the possibility to decide in what manner and with which aim of desired accuracy, economy and rapidity a given specimen has to be analyzed.
The capacity of laidlomycin (I) and the new 26-deoxylaidlomycin (II) to facilitate passive fluxes of cations through a layer of organic solvent (CHCl3/n-heptane) was estimated in comparison to monensin A (III). While II displayed a 10fold higher transport rate for sodium as compared to calcium, laidlomycin (I) was distinguishable by mediating approx. 100 times lower conveyance of the divalent cations.
In strongly acidic medium (70% HClO4) streptothricins form a fluorophore (lambda ex = 312 nm; lambda em = 381 nm) with unknown structure. A fluorimetric determination of pure or crude products and cultures, respectively, was worked out based on this reaction. Concentrations for fluorescence measurements were in the range of 10(-8) - 2 X 10(-7) moles. Interferences of the assay are discussed, a statistical evaluation of results and a comparison between microbiological and fluorimetric findings are given.
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