Morphological Studies in the Genus Nocardia Ii

Abstract

Most of these investigations concerned organisms belonging to the genus Streptomyces. Such problems as the properties of the cell wall, septation of hyphae, the nature of the cytoplasm and its contents, and the manner of cell division and spore formation have been considered. The extreme narrowness of filaments (about 1 micron) renders internal structures difficult to study; thus decisions regarding their nature have in some cases been controversial and inconclusive. The present studies were undertaken to add to the information of the cytology of actinomycetes by means of both light and electron microscopy and by the use of microchemical tests. The organisms investigated belong to the genus Nocardia (Proactinomyces), and for the most part one strain, Proactinomyces ruber (Casab6) Baldacci,8 was used. This strain was selected for detailed study because it grows well and is intermediate in morphology between forms that are bacteriumlike and those that are Streptomyces-like. METHODS AND RESULTS Morphology of old cultures. Stained preparations of 6-month-old cultures of ' This organism would now be placed in the genus Nocardia; however, the old name Is retained here, as matters of redesignation are beyond the scope of the present work. 589

The Cytochemistry of Bacterial Nuclear Structures

“…They oonsidered, however, that the cortex rather than the medulla contains the desoxypentose nucleic acid. With the electron microscope, McClung (1950) found ring-formed intracellular bodies in Proactinomyces ruber which probably were the result of the same phenomenon of electronic disintegration observed by Knaysi, Hillier, and Fabricant (1950) with the "nuclear" organelles they studied.…”

Ultrastructure of Nocardia Cell Growth and Development on Defined and Complex Agar Media

“…The genus Nocardia is characterized by forming filamentous, branched cells which fragment to shorter rod or coccoid units (20; Bergey's Manual, 7th ed.). There have been several light microscope studies of this developmental process (1, 2, 3, 14,20,21), but there have been few ultrastructural studies of Nocardia. Hagedorn (8) studied thin sections of N. corallina, but was unable to demonstrate intracytoplasmic membranes within these cells.…”

II. REPRODUCTION OF Bacterionema matruchotii1

“…(c) Two types of growth apparently exist in Actinomyces and Nocardia. Species of both genera exhibit the "angular growth" described by Qrskov (10,11). Additionally, in filaments of Actinomyces and perhaps some Nocardia species, septa are formed immediately prior to fragmentation, which often yields zigzagged rows of bacillus-like bodies similar to those described here for Bacterionema matruchotii (8,10).…”

“…(a) The bacillus-like bodies resulting from filament fragmentation do not remain as discrete entities in Actinomyces and Nocardia, but either themselves elongate to yield new filaments, or are converted into more coccoidal elements which are eventually absorbed during subsequent germination (3, 8, 10-12). (b) Dichotomous branching is more frequently found in Bacterionema than in Nocardia or Actinomyces (10,11). (c) Two types of growth apparently exist in Actinomyces and Nocardia.…”

“…At 10 hr, 15 min, showing fragmentation of the filament on the left and development of two new germination tubes from the septum originally seen.…”