Studies on the Genus Archangium (Myxobacterales) I. Morphology

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Abstract
Two 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.