Studies on the growth of Frankia isolates in relation to infectivity and nitrogen fixation (acetylene reduction)

Abstract

Several Frankia isolates were tested for their growth ability on a mineral medium containing glucose, succinic acid, or propionic acid as the sole carbon–energy source. Utilization of these nutrients allowed a preliminary discrimination between isolates. Propionic acid turned out to be a rather universal carbon source for the isolates involved in this study. In a system containing propionic acid as C–energy source and NH4Cl as N source, the development of infectivity on A. glutinosa with free-living cultures of CpI1 was followed during a growth period of 30 days. The growth pattern was compared with the development of both infective and viable units and the number of hyphal units and spores counted in mildly sonicated samples. On the same medium without NH4Cl several isolates were studied for the development of nitrogenase activity (acetylene reduction) in a growth experiment. The relation between growth and nitrogen fixation was also studied and compared in some experiments with the development of vesicles.