The Role of Haems and Related Compounds in the Nutrition and Zoosporogenesis of the Rumen Chytridiomycete Neocallimastx frontalis H8

summary: The haem requirement for growth of the rumen chytridiomycete Neocallimastx Frontalis H8 was satisfied by haem, haemin, haematin, mesoporphyrin IX, coproporphyrins I and III, uroporphyrins I and III, but not deuteroporphyrin IX. Porphyrin degradation products and precursors of porphyrin synthesis did not support growth. Protoporphyrin IX and haemato-porphyrin IX supported growth, indicating that the organism contains ferrochetalase, but was unable to synthesize the porphyrin ring. Haem could be provided by catalase and peroxidase, but not by cytochrome C. Zoosporogenesis was induced in N. Frontalis H8 in rumen fluid principally by haem, haemin and haematin, and to a smaller extent by catalase, peroxidase and protoporphyrin IX. Haem precursors and degradation products were ineffective. Chlorophylls a and b and their ruminai degradation products, plant fraction 1 protein and chelated iron neither stimulated growth nor induced zoosporogenesis. Haem induced partial zoosporogenesis in haem-limited cultures and suspensions of sporangia grown In Vitro.