SUMMARY: The organism Peshkoff, a very large, Gram-negative, peritrichously flagellated bacterium of unusual structural complexity, which Peshkoff (1940) found in cow dung near Moscow, has been isolated in pure culture from Cambridgeshire cow dung.

The organism grows only poorly on routine nutrient agar, but thrives on yeast-extract+meat-extract agar, especially if supplemented with small amounts of sodium acetate. In liquid media it does not multiply, but very small concentrations of agar are sufficient to enable it to grow.

Individual cells of have a diameter of 2·5-3·2 μ. and are 10-30 μ. long or longer. They divide by binary fission like ordinary bacteria but have in reality a chambered, many-celled structure which gives the organisms a superficial resemblance to filamentous Cyanophyceae. The cell units are either discoid or shortly cylindrical and contain configurations of Feulgen-positive chromatinic bodies, similar to, but more complex than, those found in ordinary bacteria. We regard them as nuclear structures.

The provisional name of is proposed for another very large, Gram-negative, filamentous bacterium of unusual morphology, very different from , also found in cow dung. The new organism is peritrichously flagellated and grows in filaments, 1·5 μ. wide and up to 200 μ. long. The component cells of the filaments are few in number and exceedingly long, often 20-50 μ. Fragmentation into smaller units, which is the usual fate of filamentous forms in ageing cultures of ordinary bacteria, was never observed in


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