Precipitate Formation by Metal Ions and Antibiotics, Particularly Tetracycline Substances

Many investigators have reported on the influence of various metal ions on antibiotics. The direct evidence for binding of metal ions with antibiotics is, however, very rare. The authors happened to find the precipitate formation by Mg⁺⁺ ion and aureomycin, and studied this phenomenon on various sorts of metal ions and antibiotics. The results are summarized as follows: 1) A marked yellow precipitate was formed by 10⁻² 10⁻³ M Mg⁺⁺ and 10⁻³-10⁻⁴M aureomycin. 2) A yellow precipitate was formed by 10⁻³M Mn⁺⁺ and 10⁻³-10⁻⁴M aureomycin, and was also formed by 10⁻⁴M Mn⁺⁺ and 10⁻³M aureomycin. 3) Just, like aureomycin, terramycin formed a yellow precipitate in the presence of Mg⁺⁺ or Mn⁺⁺. The degree of precipitate formation was, however, very weak as compared with aureomycin. 4) The precipitate formation between Mg⁺⁺ and aureomycin appeared at the pHs over 6.5 and became more marked with the rise of pH. 5) The acid solution of the yellow precipitate formed by Mg⁺⁺ and aureomycin showed a strong antibacterial action

A Physiological Aspect of the Citric Acid Cycle of Micrococcus pyogenes var. aureus (Terashima)

In 1957, Yabe reported that the combined administration of glutamate and glucose markedly accelerated the respiration of Micrococcus pyogenes var. aureus (Terashima) over the sum of those in each of the two substrates, and that this phenomenon was due to the important role of glutamate as a sole sparker or entering site of the citric acid cycle of M. pyogenes var. aureus (Terashima). In the present experiments, the authors investigated this phenomenon in regard to pH. In the presence of glutamate and glucose, oxygen consumption or carbon dioxide evolution was nearly the same at all pHs tested, whereas ammonia formation was the best at pH 6.2, which was the optimum for glutamate oxidation by M. pyogenes var. aureus (Terashima); this result seems to sustain the conclusion given by Yabe. For all of glutamate, aspartate and alanine, the oxidation optimum pHs were lower in M. pyogenes var. aureus (Terashima) than in pyogenes var. albus and citreus. From thsee results, it is easily inferred that the cytoplasmic membrane of M. pyogenes var. aureus (Terashima) is a pretty peculiar one compared with those of the other two micrococci, and that these peculiar physiological properties of the cytoplasmic membrane have something to do with the previously reported peculiar aspect of the citric acid cycle of M. pyogenes var. aureus (Terashima)

A Comparative Study on the Action of Aureomycin and Terramycin

Both of aureomycin and terramycin belong to the tetracycline, and their action has been considered to be nearly the same. The authors made a comparative study on the action of aureomycin and terramycin and obtained the following results: 1) The respiration of Escherichia coli in the presence of glucose, pyruvate, aspartate and glutamate is markedly inhibited by both of aureomycin and terramycin. The respiration inhibitory action of aureomycin is quantitatively about 3 times higher than that of terramycin. 2) The respiration of Micrococcus pyogenes var. aureus (Terashima) in the presence of glutamate, alanine, pyruvate and lactate is inhibited by both of aureomycin and terramycin. As for the respiration inhibitory action, aureomycin is quantitatively about 3 times stronger than terramycin. 3) The respiration of M. pyogenes var. sureus (Terashima) in the presence of glucose is not inhibited by aureomycin or terramycin, but is rather accelerated by these, particularly by terramycin. 4) As for the growth inhibitory action, aureomycin is somewnat stronger than terramycin

Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu

International audienceC-type asteroids1 are considered to be primitive small Solar System bodies enriched in water and organics, providing clues to the origin and evolution of the Solar System and the building blocks of life. C-type asteroid 162173 Ryugu has been characterized by remote sensing2-7 and on-asteroid measurements8,9 with Hayabusa2 (ref. 10). However, the ground truth provided by laboratory analysis of returned samples is invaluable to determine the fine properties of asteroids and other planetary bodies. We report preliminary results of analyses on returned samples from Ryugu of the particle size distribution, density and porosity, spectral properties and textural properties, and the results of a search for Ca-Al-rich inclusions (CAIs) and chondrules. The bulk sample mainly consists of rugged and smooth particles of millimetre to submillimetre size, confirming that the physical and chemical properties were not altered during the return from the asteroid. The power index of its size distribution is shallower than that of the surface boulder observed on Ryugu11, indicating differences in the returned Ryugu samples. The average of the estimated bulk densities of Ryugu sample particles is 1,282 ± 231 kg m−3, which is lower than that of meteorites12, suggesting a high microporosity down to the millimetre scale, extending centimetre-scale estimates from thermal measurements5,9. The extremely dark optical to near-infrared reflectance and spectral profile with weak absorptions at 2.7 and 3.4 μm imply a carbonaceous composition with indigenous aqueous alteration, matching the global average of Ryugu3,4 and confirming that the sample is representative of the asteroid. Together with the absence of submillimetre CAIs and chondrules, these features indicate that Ryugu is most similar to CI chondrites but has lower albedo, higher porosity and more fragile characteristics