Biosynthesis of the Antibiotic Nisin by Whole Streptococcus lactis Organisms

Abstract

SUMMARYA reaction mixture is described consisting of a buffered solution of amino acids, salts, growth factors and glucose in which freshly harvested washed Streptococcus Zactis incorporated radioactive tracers and synthesized nisin. Rapid nisin synthesis started after a delay of 30-60 min. but bacteria pre-incubated in the reaction mixture synthesized nisin without delay although the rate of protein synthesis remained the same as that of freshly harvested bacteria. Although growing S . Zactis is sensitive to penicillin and mitomycin these antibiotics had no effect on nisin synthesis by washed organisms. Actinomycin D inhibited uptake of tritiated uridine immediately and inhibited nisin synthesis after a delay of about 60 min. Antibiotics which interfere with protein synthesis, e.g. chloramphenicol, puromycin and terramycin also interfered with nisin synthesis. The inhibition was immediate and occurred irrespective of whether the antibiotics were added a t the beginning of an experiment or after 50 min. Nisin synthesis was more sensitive than protein synthesis. The data suggest that nisin synthesis occurs by a mechanism similar to that of protein synthesis.

Biosynthesis of the Antibiotic Nisin and Other Basic Peptides by Streptococcus lactis Grown in Batch Culture

“…Washed suspensions of Streptococcus Eactis synthesized nisin by a mechanism which was similar to that of protein synthesis, in that i t was sensitive to inhibition by chloramphenicol and puromycin but differed by being more sensitive to these antibiotics and synthesis was always preceded by a delay (Hurst, 1966). Growing cultures also show a delay of synthesis of nisin since this did not start till the logarithmic phase of growth (Hirsch, 1951).…”

“…It was suggested (Hurst, 1966) that nisin synthesis resembles protein synthesis. Cheeseman & Berridge (1957) suggested that the molecular weight of nisin was 7000; this puts i t in the class of small proteins.…”

“…Organisms, media and culture conditions were described before (Hurst, 1966) For cultivation experiments the nisin producing Streptococcus lactis was subcultured twice a t 24 hr intervals and then used as inoculum for batch culture. Immediately before inoculation the culture was diluted with an equal volume of medium 22 prewarmed to 30" and incubated for 1 hr a t 30'; the volume was adjusted to give a 5 yo (v/v) inoculum.…”

“…Nisin (free and bound = total nisin) was estimated by the modified method of Berridge & Barrett as previously described (Hurst, 1966). For estimating nisin bound to the organisms (cellular nisin) the reaction was stopped by chilling, the organisms centrifuged down in the cold and the supernatant fluid replaced by an equal volume of 0.05 N-HC~ in which the cocci were resuspended.…”

Observations on the Action of Benzylpenicillin on a Strain of Streptococcus Lactis

“…light path, and by gravimetric determination of terminal organism dry weights. pH values were determined electrometrically and nisin by bioassay (Hurst, 1966). Most probable numbers.…”