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A sisomicin fermentation carried out in the presence of (methyl-14C)-L-methionine resulted in a crude mixture, composed of methyl-14C-labeled sisomicin as a major component; and two 4''-C-desmethylsisomicin (66-40B and 66-40D) isomer-like components, an unidentified component and a gentamicin A-like antibiotic as minor components. When (methyl-14C)-L-methionine was added in an early stage of the fermentation (24 hours), incorporation of methyl-14C-label into polar components (e.g., gentamicin A-like antibiotic) preceded that into sisomicin. Chromatographic evidence for the bioconversion of (methyl-14C)-gentamicin A to a radioactive sisomicin-like product (possibly (3''-N-methyl-14C)-sisomicin) was seen, when a Micromonospora blocked mutant was incubated in the presence of the former antibiotic.

Studies of the microbial conversion of progesterone to Δ1,4-androstadiene-3,17-dione by Streptomyces lavendulae and to 16α-hydroxyprogesterone by Streptomyces sp. ATCC 11,009 have shown that a lag in metabolism of the steroid occurs when the progesterone is added to washed cells of these organisms grown in a medium containing soybean meal, glucose, and calcium carbonate. No lag was observed when the cells were grown in this medium supplemented with a trace of progesterone. Addition to the cell suspensions of sufficient quantities of streptomycin sulphate, viomycin sulphate, dihydrostreptomycin sulphate, neomycin B sulphate, or tetracycline hydrochloride (to give a concentration of 10 μg. per ml.) coincident with the addition of the progesterone resulted in complete inhibition of steroid oxidation. When addition of the antibiotics was delayed until 12 hours after addition of the progesterone or the cells were grown in a medium containing a trace of progesterone, practically no inhibition was observed. These experiments suggest that the enzymes formed in these two streptomycetes which carry out the transformation of progesterone are adaptive in origin.