The taxonomic description of Streptomyces laurentii, a new species related to but distinguishable from the S. fradiae group, is presented. This new species produces thiostrepton but bears no taxonomic relationship to the known producers of the antibiotic: S. azureus, S. hawaiiensis, and Streptomyces X-14b.
Nucleic acids from Streptomyces griseus178 were isolated during cultivation. After their fractionation on a column of methylated serum albumin adsorbed on Kieselguhr, the 16 S and 23 S RNA were isolated. To characterize RNAs their sedimentation coefficients, Tm and nucleotide composition were determined. During cultivation of S. griseus 178 rRNA level reaches two maximum peaks and the production of streptomycin influences nucleic acids of the producer organism.
Streptomyces nogalater, UCR-2783, and Streptomyces peucetius var. caesius, IMRU-3920/UCR-5633, catalyze ketonic carbonyl reduction of steffimycinone (1, Scheme 1). Using cell-free preparations of S. nogalater, the process of ketonic carbonyl reduction has been shown to be TPNH linked. The product, steffimycinol (2), is reduced further by Aeronlonas hydrophila, 2C/UCR-6303, by the process of microaerophilic conversion of anthracyclinones previously reported1, 2) with the result being the formation of 7-deoxysteffimycinol (3). The products (2 and3) were isolated by extraction from the fermentations followed by chromatographic purification. Identification was by comparison of various physical properties and spectral data with those of authentic materials obtained by chemical means. Catalytic activity of the crude enzyme preparations of S. nogalater was lost by dialysis but restored by addition of TPNH although not by addition of DPNH demonstrating TPNH dependence. The reaction rate increased linearly with added crude enzyme protein up to 4mg/ml and was highest between pH 6.5 and 7.0.
Four hundred and thirty-five Staphylococcus aureus strains and 395 strains of gram-negative 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.
A wild strain of Staphylococcus aureus which inactivates a wide variety of antibiotics has been found to inactivate pristinamycin IIA, an antistaphylococcal antibiotic. This phenomenon has been demonstrated to be plasmid mediated. The plasmid directs the biosynthesis of an acetyltransferase which is able to O-acetylate the drug. We propose to call the new enzyme PAC (IIA): Pristinamycin acetyltransferase.