Specificity of the Heme Requirement for Growth of Bacteroides ruminicola

Abstract

Previous studies suggested that most strains of B. ruminicola subsp. ruminicola require heme for growth. Present studies with heme-re-quiring strain-23 showed that protoheme was replaced by various por-phyrins, uroporphyrinogen, coproporphyrinogen, certain iron-free metalloporphyrins, hemes, and certain heme-proteins containing readily removable hemes. Strain-23 utilized a wider range of tetrapyrroles than hemin-requiring bacteria previously studied. Inactive compounds included porphyrin biosynthesis intermediates preceding the tetrapyrrole stage and related compounds; uroporphyrin, chlorophyll, pheophytin, phycoerythrin, bilirubin, pyrrole, FeSO4 with or without chelating agents; and representative ferrichrome compounds. Strain-23, two other strains representing predominant biotypes of B. ruminicola subsp. ruminicola, and one closely related strain grew in media containing heme-free protoporphyrin, mesopor-phyrin, hematoporphyrin, or deuteroporphyrin, apparently inserting iron into several nonvinyl porphyrins. Porphobilinogen and porphyrin synthesis, apparently via the commonly known heme synthesis pathway, occured during growth of heme-independent B. ruminicola subsp. brevis strain-GA33 in a tetrapyrrole-free medium containing [delta]-aminolevulinic acid, but [delta]-aminolevulinic acid metabolism to porphobilinogen or porphyrins could not be detected in cells of heme-requiring strain-23 grown in the same medium with hemin added. Growth of strain-23 with uroporphyrinogen, coproporphyrinogen, or protoporphyrin-IX replacing hemin suggests that part of the commonly known heme-biosynthesis pathway is present in this strain, but nutritional and metabolic evidence indicates that some or all of the enzymes synthesizing the tetrapyrrole nucleus from linear molecules are lacking or inactive.