Comparison of the developmental cycles of some members of the genus Nocardia

Adams, James N. (University of Georgia, Athens) and Norvel M. McClung. Comparison of the developmental cycles of some members of the genus Nocardia. J. Bacteriol. 84:206-216. 1962.-A staining technique specific for cell walls was used to determine the characteristic development of Nocardia rubra, N. erythropolis, N. asteroides, and N. canicruria comb. nov. When inoculated on a fresh medium, these organisms were observed to germinate, with the production of one or more germ tubes from coccoid, ovoid, and short bacillary cells. Upon continued incubation, the germ tubes elongated to form filaments from which branches could be formed. Two other mechanisms of branching were noted. One was a result of multiple germination of cells and the other a result of single or multiple germination of short chains of cells. Both of these mechanisms could be readily differentiated from true branching. Mycelial formation varied in extent among the species studied and was governed, in part, by the types of branching which an organism exhibited. After the phase of branching development has been completed, fragmentation of the filaments and branches occurred as a result of the separation of the corresponding filament fragments following the random deposition of septa along the lengths of the cells. As the culture age increased, the separating filament fragments became shorter until they ultimately reached sizes like those of cells found in the inoculum. The observed developmental cycles of the genus Nocardia were compared to those which have been described for the genera Mycobacterium and Streptomyces, and the taxonomic implications of the differences between these developmental cycles was discussed.