One hundred and sixty-seven pure cultures have been isolated from among 338 myxobacteria obtained from Essex county (Ontario) soil samples by various methods. The fruiting body characteristics used in the characterization of the Myxobacterales have been found to be variable and unstable. However, the order may be considered to consist of two broad groups based on vegetative cell morphology and the formation of microcysts. A proposal is made to divide the genus Chondromyces into Stigmatella and Chondromyces and to assign the latter to the family Sorangiaceae. A number of biochemical tests have been found useful in identification and some are correlated with morphological features.The paper includes 42 color photographs as an aid for other investigators in the identification of the Myxobacterales.

Of twenty-two strains of gliding prokaryotes examined, all but three were found to possess polar fimbriae. Fimbriae were not observed on two gliders, while Chloroflexus aurantiacus bore abundant peritrichous fimbriae. In some gliding bacteria, fimbriae were associated with 'holes' surrounded by an electron-transparent collar bearing 12 spike-like projections.

Electron microscopy of sectioned, chemically fixed Chondromyces crocatus revealed a microorganism with a typical gram-negative cell envelope. The cytoplasm contained, in addition to tubules and two types of granules, a membrane-associated structure (MAS) that, although less extensive, bears some resemblance to polar membranes observed in flagellated bacteria. Examination of swarming cells negatively stained in situ, as well as thin sections, established that cell division occurs by septum formation and that well-defined mesosomes are associated with the process. Polar pili and a compact, amorphous slime layer surrounding the cells were evident in shadowed preparations of in situ cells. The slime layer and pili, by providing cell-to-cell interconnections, may influence the organized gliding movement characteristic of C. crocatus and other myxobacteria.

The discovery (9) that the development of a new aquatic fungus, Blastocladiella emersonii, along either of two distinct morphogenetic pathways leading to ordinary colorless (OC) or resistant sporangial (RS) plants could be determined by a simple manipulation of the external environment, presented an excellent opportunity for studying the relationship between metabolism and morphogenesis. Even with this very simple, two-celled organism, however, almost a model system in fact, the relationship is a complex one, and the progress of our understanding inevitably slow. The comparatively recent finding (14) that light plays a role in development has added an interesting but complicating aspect to the story.Studies during the past decade have led us (11, 13, 18, 58) to postulate mechanisms for the morphogenetic and light phenomena in Blastocladiella. An integral part of these is the key role of an enzyme, isocitritase; its presence was implied but not explicitly demonstrated. In the work reported here, the presence of isocitritase in Blastocladiella has been confirmed, the enzyme partially purified, and its properties studied. A second enzyme, glycine-alanine trailisaminase, presumably involved in the in vivo role of isocitritase, has been similarly examined. After the development of new culture techniques, the relationship of these enzymes to differentiation was investigated in detail.

No abstract