RESUMO
The effects of adding chloramphenicol before inoculation and during exponential growth of Streptomyces venezuelae (3022a) in fermentors were studied. The responses of the organism during synthesis of chloramphenicol (in a glycerol-serine-lactate medium) were compared with those in media supporting less (glycerol-nutrient broth-yeast extract) or no synthesis (glucosemineral salts). In systems where little or no synthesis of the chloramphenicol occurred, addition of the antibiotic induced micromorphological and ultrastructural abnormalities similar to those reported for sensitive bacteria. There was also an increase in the frequency of mesosomes and electron-light areas. It was suggested that the former may be associated with activity of chloramphenicol hydrolase and the latter with storage and/or excretion of the breakdown product; N-acetyl p-nitro-phenylserinol. When chloramphenicol synthesis occurred, addition of the antibiotic had less effect on the micromorphology or ultrastructure of S. venezuelae as permeability barriers to external chloramphenicol had been established. Electron-light areas were frequent, possibly being associated with storage and excretion of precursors of chloramphenicol.
Assuntos
Cloranfenicol/farmacologia , Streptomyces/efeitos dos fármacos , Membrana Celular/ultraestrutura , Parede Celular/ultraestrutura , Cloranfenicol/biossíntese , Meios de Cultura , Streptomyces/crescimento & desenvolvimento , Streptomyces/ultraestruturaRESUMO
Streptomyces venezuelae (3022a) was grown in flask cultures and fermentors, using three media having differential effects on chloramphenicol production. Micromorphology, ultrastructure and chloramphenicol concentrations were studied during the growth cycle in each medium. Chloramphenicol production was greatest in the glycerol-serine-lactate (GSL) medium, less in the glycerol-nutrient broth-yeast extract (GNY) medium and very low in glucose-mineral salts (GA) medium. In GSL and GA, much growth was in the form of microcolonies, especially in flask cultures, while short hyphal fragments predominated in GNY. The major ultrastructural features were the high frequency of mesosomes in fragmenting hyphae in GNY, and electron-transparent zones which appeared during chloramphenicol synthesis in GSL. None of the structural abnormalities induced by chloramphenicol in sensitive organisms were observed in S. venezuelae despite high levels of the antibiotic in GSL medium.