Hyphae Differentiation And Development Of Streptomyces Viridoeharongenes E-219

The Steptomyces has complex developmental cycle. It can produce secondary metabolites in the process of morphological differentiation. There is a close relationship between the complex developmental cycle and the secondary metabolism. Avilamycin is an oligosaccharide antibiotic which belongs to orthosomycin. It is produced by Streptomyces viridoehrongenes. Recently, considerable research efforts have been focused mainly on the screening of high avilamycin-producing strains, biosynthetic gene cluster and biosynthetic pathway of avilamycin; however, there is little information about the morphological differentiation, programmed cell death and the relationship between the developmental cycle and the secondary metabolism in Streptomyces viridoehrongenes.In this paper, the developmental cycle and programmed cell death of Streptomyces viridochromogenes E-219, which was a fusant which derived from Streptomyces viridochromogenes1315treated with60Coγ-rays irradiation and protoplast fusion, were studied on solid and in submerged culture. The relationship between the developmental cycle and the secondary metabolism of the Streptomyces viridoehrongenes E-219also were supposed.Morphological differentiation characters such colony, hyphae and conidiophores of original strain1315and mutant strain E-219were investigated by scanning electron microscope and fluorescence microscope. The results showed that the strain E-219presented a significant difference to the original strain1315. Cultured on solid surface, Strain1315had dense velvet, grayish-green colony, spiral sporotrichial and round conidiophore with spike, whereas strain E-219had umbilical boss, white colony, linear sporotrichial, smooth and cylindrical conidiophore.With the help of fluorescent probes, fluorescence microscope and electron microscopy, the morphology differention and development of Streptomyces viridochromogenes strain E-219were investigated on solid culture. The developmental and differentiatial cycle of longitudinal sections obtained from mutant strain E-219has six growing phases,(ⅰ) germination and formed variegated hyphae,(ⅱ) variegated hyphae development and the formation of a single colony,(ⅲ) profuse growth of the live segments derived from the variegated hyphae,(ⅳ) the apoptosis of the second mycelium,(v) profuse growth of live mycelium, and (vi) sporulation. The developmental and differentiatial cycle of transverse sections obtained from mutant strain E-219also has six growing phases,(i) germination and formed variegated hyphae,(ii) variegated hyphae development and the formation of mycelium layer in the solid substrate,(iii) profuse growth of the live segments derived from the variegated hyphae,(iv) the apoptosis of the second mycelium,(v) profuse growth of live mycelium, and (vi) sporulation. It is the fist time to states that cell apoptosis existed in the first hyphae in the Streptomyces viridochromogenes. Compared with the developmental and differentiatial cycle of original strain1315, strain E-219has the phase of the development of variegated hyphae and the phase of profuse growth of the live segments derived from the variegated hyphae.Streptomyces viridoehrongenes E-219would experience three growth phases in one complete developmental process in submerged culture. The first phase was germination and compartmentalized of first mycelium development. The second phase was growth arrest. The third phase was the development of second mycelium which developed as a syncytium with sporadic septa. Compared with original strain1315, mutant strain has distinct and temporary growth arrest phase. Furthermore, its pellets were smaller diameters than those of original strain1315.The morphological differentiation and the growth metabolism of Streptomyces viridoehrongenes were studied. Growth curves were obtained from Streptomyces viridoehrongenes E-219and1315. There are two distinct stages of exponential growth separated by a temporary growth arrest phase. The two waves of exponential growth correspond to the development of the first, compartmentalized, mycelium and the growth of the second, multinucleated, mycelium. The kinetics involved in the production of avilamycin was analyzed within the context of the developmental phases. Antibiotic production commences on the transient growth arrest phase, and antibiotic appearance correlates strongly with the development of the second, multinucleated, mycelium.The cell apoptosis during the process of morphological differentiation on solid culture and in submerged culture were studied. We report that the Streptomyces viridoehrongenes exists cell apoptosis. Several indicators, such plasma membrane disruption, DNA degradation and release of the cytoplasmic content into exocellular medium, support the occurrence of cell apoptosis.