Studies on the Genus Archangium (Myxobacterales) I. Morphology

SUMMARYTwo Archangium isolates, A. primigenium and A. gephyra, were secured from soil and elm tree bark. Pure cultures were established and maintained on a variety of media. Agar plates containing rabbit dung and rabbit dung decoction agar proved most useful. The cultures were incubated at 22–26 C.Vegetative rods of A. gephyra averaged 10.5 × 0.6 μ, while A. primigenium averaged 7 × 1.2 μ. Cells were needle-like, tapering slightly to blunt, rounded ends. Characteristic gliding and oscillating movements were observed for both species.Colonial morphology was similar for both species. A flat, thin sheet of cells with a microscopically irregular periphery was typical. The texture of the colonial mass varied in consistency.Fructification was observed in liquid and on solid media. In a liquid medium, atypical, star-like clusters culminated in a solid mass of shortened rods. On solid media, circular and wave-like masses of cells joined to form a mound of cells which matured into the typical, tubular, fruiting body mass.Fruiting bodies from soil or bark averaged 1 mm2 or smaller in size. When grown in pure culture, fruiting bodies coalesced to cover areas of over 20 mm2. Fruiting bodies were usually enveloped in a slime layer. Encysted rods of A. primigenium averaged 4.5 × 0.9 μ in size and A. gephyra 2.5 × 1.4 μ.Germination of fruiting bodies followed either of two patterns both resulting in normal, migrating colonies. Activated rods either pulsed forth from a germinating fruiting body or projected perpendicularly from the surface of the entire fruiting body as quills on a porcupine.Carotene as a component of Archangium pigmentation was ascertained by using conc. H2SO4. Loss of pigmentation by a fruiting body indicated loss of viability. Standard nuclear stains produced dense areas within vegetative cells and granulations. Granulations also occurred when 5% methylene blue was employed. All rods were gram-negative and non-acid fast.