Biosynthesis of peptides containing α-aminoadipic acid and cysteine in extracts of a <i>Cephalosporium</i> sp

1. Three intracellular peptides found in small amount in a Cephalosporium sp. were rapidly labelled when dl-[14C]valine was added to a shaken suspension of the organism. More 14C was incorporated into peptide P3, δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine, than into peptide P2 (containing α-aminoadipic acid, cysteine, valine and glycine) or peptide P1 (containing β-hydroxyvaline in place of the valine in peptide P2). 2. Peptides P3 and P2, but not peptide P1 were formed in a broken-cell system from the Cephalosporium sp. in the presence of δ-(l-α-aminoadipyl)-l-cysteine and dl-[14C]valine. No synthesis was observed in the presence of δ-(d-α-aminoadipyl)-l-cysteine or of dl-α-amino[14C]adipic acid and l-cysteinyl-l-valine or l-cysteinyl-d-valine. 3. The biosynthesis of these peptides was catalysed by the particulate fraction of the broken-cell system, whereas that of glutathione was catalysed by the supernatant fraction. 4. These results are discussed in relation to penicillin N and cephalosporin C biosynthesis.</jats:p

Measurement of Three Antibiotics (Penicillin, Cephalothin, and Chloramphenicol) When Present Together in Mixtures

Benzylpenicillin, cephalothin, and chloramphenicol were measured individually and quantitatively when present together in mixtures at concentrations found in patients. The assay depended on the selective inactivation of two of the antibiotics, permitting the third to be assayed as if present alone. Agar seeded with a chloramphenicol-resistant, penicillinase-negative Staphylococcus aureus was used for a cylinder-plate assay of appropriately diluted fluid to determine the activity of either benzylpenicillin or cephalothin after either β-lactamase inactivation of the former or ultraviolet light inactivation of the latter. Chloramphenicol was assayed with Sarcina lutea after appropriate β-lactamase inactivation of both cephalothin and benzylpenicillin. Fluids containing various amounts of the three antibiotics were assayed by this method with less than 8% error. Procedures that fail to measure each antibiotic individually may give larger errors. </jats:p

Enhancing Effect of Alkalinization of the Medium on the Activity of Erythromycin Against Gram-negative Bacteria

The antibacterial activity of erythromycin was markedly enhanced by alkalinization of the culture medium or urine within the clinical range ( p H 6.0 to 8.2). This effect was demonstrated against recent isolates of Escherichia coli, Klebsiella pneumoniae, Enterobacter sp., and Pseudomonas aeruginosa , as well as against Staphylococcus aureus and Streptococcus faecalis . The urine of normal volunteers was made alkaline by ingestion of sodium bicarbonate or acetazolamide (Diamox) during administration of 1.0 g of erythromycin every 8 hr; such urine was capable of inhibiting E. coli and K. pneumoniae even when diluted up to (in one instance) 128 times with broth of the same p H as the urine. Undiluted urine of the same subjects, without alkalinization, was seldom capable of inhibiting these organisms. The range of p H (6.6 to 8.6) over which the antibacterial effect was enhanced coincided with that over which there was decreasing ionization of a basic group. </jats:p