Three proteases, namely chymotrypsin-like protease (CTP), trypsin-like protease (TLP) and metalloprotease (MTP), were identified in cultures of Streptomyces albidoflaws SMF301. The dynamics of protease production were determined and the roles of the proteases in morphological differentiation were deduced to be as follows: CTP is essential for hydrolysing the proteinaceous nitrogen source for mycelium growth; TLP plays a role in the formation of thickened mycelium in submerged culture and of aerial mycelium in solid culture; MTP may participate in the maturation of spores. The unique thickened mycelia in submerged culture are thought to be an intermediate form between mycelium and spores. TLP (molecular mass 32 kDa) and MTP (molecular mass 18 kDa) were purified and their enzymic properties were determined.
We report the first quantitative analysis of the relationship between environmental changes and sporulation of a streptomycete, Streptomyces albidoflavus SMF301, in submerged culture. A chemically defined medium was constructed for sporulation, over lo9 spores ml-l being formed in the submerged batch culture. Kinetic parameters calculated from batch and chemostat cultures showed that specific submerged spore formation rate (qSJ was inversely related to the specific mycelial growth rate (p). The optimum growth rate for submerged spore formation was 005 h-l, when the maximum value of qrpo was 1.0 x lo6 spores g-l h-l. The turnover rate of biomass at maximum growth yield was 0.029 h-I, when 5.6 x lo6 spores were formed from 1 g mycelium. The present quantitative analysis of submerged spore formation using a controlled system opens the way for biochemical and molecular biological studies related t o the morphological differentiation of Streptomyces spp.
Stveptomyces albidoflavus SMF301 produced abundant spores in submerged cultures (submerged spores) as well as on solid media (aerial spores). The content of carbon, hydrogen, nitrogen, and phosphorus in submerged and aerial spores was similar; however, the contents of metal ions (K+, Na+, Ca2+ and Mg2+) were very different. Glutamic acid, alanine, and glycine, all known to be cell-wall components, were the major amino acids in both types of spores. However, cysteine was more abundant in submerged spores than in aerial spores. The major fatty acid in aerial spores was n-C,, (61.74%), whereas in submerged spores it was ai-C,, (33.68%). The contents of ai-C,,, and ai-C,, in submerged spores were also very much higher than in aerial spores. Unsaturated fatty acids were found in both kinds of spores but not in mycelium; they were particularly abundant in submerged spores. The composition of menaquinones in the two kinds of spores also varied. The resistance of aerial spores to lysozyme digestion, mild acid treatment, heating and desiccation was higher than that of submerged spores, but the submerged spores were more resistant to sonication.
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