SUMMARY: The morphological and cultural characteristics of seven recently isolated strains of closely resembled those given by previous authors. Fermentation reactions were unsatisfactory, owing to the production of acid in basal media without added carbohydrate. The growth of two strains studied in detail was greatly facilitated by X factor and to a much smaller extent by V factor; it was best on chocolate agar. The strains were non-pathogenic in mice. Serologically, they behaved alike in precipitin and complement-fixation tests. There was insufficient information to classify them into subtypes.

The black pigment, extracted by a new technique which avoids the use at any stage of alkalis, proved to be haematin (not melanin), united in the cells with a bacterial protein to form a parahaematin. Crystalline pyridine haemochromogen and haemin have been prepared from the isolated pigment. The haemin when coupled with renatured ox globin gave reconstituted methaemoglobin, oxy- and carboxy-haemoglobins. Ultra-violet and visible spectral absorption data support the identification of the pigments. In particular, the possible reduction of the vinyl groups of the porphyrin nucleus by the organism, leading to meso- or deuterohaematin, has been excluded.

It is suggested that the organism be assigned to the genus Rusiformis, and the specific name be altered from melaninogenicus to nigrescens, making Fusifomis nigrescens


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