Surface structures of new and lesser known species of thermobifida as revealed by scanning electron microscopy.

Surface structures of representatives of the genus Thermobifida were examined by scanning electron microscopy. Spores formed at the tips of multibranched sporophores initially resembled short sausages; then, upon maturation, they gradually built up their typical ovoid shape. Characteristic differences were observed between T. cellulolytica strain TB108 and T. fusca strains TM51. The spores of TB108 were larger (0.8x 1.3 microm) than those of TM51 (0.6 x 1.1 microm) in consequence of the more thickened outer squamous layer. When Thermobifida strains were grown on cellulose as sole carbon source, the mycelium was found to coil around the cellulose crystals and multiple protuberances emerged, resulting in a scabrous appearance to the mycelial surface. The presence of these cellulosome-like structures yielded a 24.5% surface enlargement of the scabrous mycelium as compared with the smooth one. The cellulosome emergence pattern paralleled the proportional increase in free endoglucanase activity measured during the culturing of these actinomycetes in the presence of cellulose.