Mycobacteriophage D29 has a head of uniform size (average diameter 65 nm) and regular shape and a tail of variable length. The stability of the bacteriophage is optimal between pH 9 and 10. The virus contains double‐stranded DNA and six structural polypeptides, three major and three minor. The molecular weights of these six polypeptides, as determined by polyacrylamide gel electrophoresis in the presence of dodecylsulfate, are 150000, 138000, 13000, 66000 and 24000. The virus contains no lipids as shown by (a) the lack of structural changes after inactivation of the bacteriophage with chloroform, (b) the absence of lipids containing [32P]phosphate or [35S]sulfate in labeled virus, and (c) the absence of an electron paramagnetic resonance spectrum in bacteriophage which had been incubated with a nitroxide‐containing fatty acid.
Four hundred and thirty-five Staphylococcus aureus strains and 395 strains of gramnegative bacteria were tested for susceptibility to gentamicin, sisomicin, tobramycin, netilmicin and amikacin. None of the staphylococcal strains were resistant to the 5 drugs, except two strains that were resistant to amikacin. Eighteen percent of the gram-negative bacteria were resistant to gentamicin, 16% to tobramycin, 14% to sisomicin, 7 % to netilmicin and 2 % to amikacin. Tests from representative strains showed that these differences were mainly due to the production of aminoglycoside-modifying enzymes. The lower incidence of strains resistant to sisomicin compared to gentamicin was due to a slightly better antimicrobial activity of sisomicin.Results of experiments on the efficiency of enzymatic phosphorylation, acetylation and adenylylation, and the inactivation of aminoglycoside antibiotics were not always in concurrence with the degree of phenotypic expression of resistance. Thus, the aminoglycoside 3'-phosphotransferase of staphylococci modified amikacin, but the strains were susceptible to the drug. Similarly, the aminoglycoside 2"-nucleotidyltransferase from members of Enterobacteriaceae and Pseudomonas efficiently adenylylated and inactivated netilmicin, but the strains were susceptible to netilmicin. On the other hand, there can be factors, intrinsically inherent in some strains, contributing to their phenotypic expression of resistance level. It is inferred, therefore, that the contribution of enzymes to the degree of resistance to aminoglycoside antibiotics in a given strain can be evaluated only by comparative examination of resistance in the wild type strain and its corresponding enzyme-negative variant.
Escherichia coli SS142 has been found to adhere specifically to the human epithelioid tissue culture cell line Intestine 407, but not to other tissue culture cells. This paper describes an accurate, reproducible and objective method of assessing the rate of adhesion of radiolabelled bacteria to these cellular monolayers. Adhesion was found to be linear with time for 60 min and with bacterial concentrations up to 10(9) bacteria/ml. The binding appeared to be irreversible. Adhesion was not affected by changes in the composition of the medium, its pH or ionic strength, or by the assay temperature within physiological limits, but was diminished at very high ionic strength or low temperature. It increased with increasing cell density of the monolayers. Under appropriate conditions the assay could be used for comparative determinations of the rate of adhesion of different, or differently treated bacteria.
The seeds of Strophanthus kombé Oliv. are known to contain high levels of cardioactive compounds. However, the therapeutic use of Strophanthus in the treatment of cardiopathy requires more detailed knowledge of the compound profile to profit from the full potential of Strophanthus preparations. Therefore, the objective was to characterize the cardenolide profile and lipophilic constituents in S. kombé seeds using methods applicable in routine quality control. Freshly prepared S. kombé seed extracts were analyzed without previous sample clean-up using a novel HPLC-DAD-MSn method. In addition, seed oils were analyzed by GC-MS following derivatization of the lipids. More than 20 cardenolides were tentatively assigned in the seed extracts including strophanthidin, strophanthidol, periplogenin and strophanthidinic acid aglycones, carrying various saccharide moieties. The findings revealed the presence of eight novel cardenolides, which have not been described for S. kombé so far. The occurrence of strophanthidinic acid derivatives was verified by comparison with synthesized strophanthidinic acid-cymaropyranoside. GC-MS characterization of the oils mainly revealed the presence of fatty acids, especially oleic acid and linoleic acid, as well as phytosterols, the latter representing intermediates of cardenolide biosynthesis. In summary, these findings broaden our knowledge on the secondary metabolism of Strophanthus.
An unsaturated fatty acid auxotroph, strain UFA, isolated from the marine pseudomonad Pseudomonas BAL‐31, host cell of the lipid‐containing bacteriophage PM2, was grown in media supplemented with different unsaturated fatty acids. Under these conditions the fatty acid composition of the cell could be altered drastically. The phase transition in the native membrane and in the extracted lipids was analyzed by electron spin resonance using a nitroxide spin probe. Membranes prepared from strain UFA grown in cisl6: 1 or trans16:1 showed one transition at 9.4 °C and 12.4 °C respectively. Extracted lipids in both cases had almost the same transition temperature as that of the intact membrane. Membranes prepared from Pseudomonas BAL‐31 had one transition at ∼ 12 °C, on the other hand there was no clear cut phase transition using extracted lipids. Replication of bacteriophage PM 2 took place below the transition temperature of the membrane lipids in the case where strain UFA was grown in trans 16: 1. Other cases were not studied.
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