Tetrapyrrole utilization by Bacteroids ruminocola.

Abstract

Reduced versus oxidized difference spectra of whole cells and pyridine hemochromogens of heme-requiring isolates of Bacteroides ruminicola are altered when deuteroporphyrin or mesoporphyrin replaces protoheme as a growth factor. During growth in the presence of either deuteroporphyrin or mesoporphyrin, whole cells exhibit peaks at 545 t547, 515 to 518, and 412 to 413 nm. Pyridine hemochromogen spectra confirm the presence of meso -or deuteroheme in cells grown in the presence of meso- or deuteroporphyrin. No evidence was found for the conversion of either meso- or deuteroporphyrin to protoheme. Cells grown in the presence of the manganese of magnesium chelates of protoheme form iron-containing hemes. Neither spontaneous decomposition of noniron metalloporphyrin chelates nor spontaneous formation of hemes from Fe2+ and metal-free porphyrins was detected. Protoheme-synthesizing isolates of B. ruminicola fail to use preformed metal-free porphyrins, but form both protoheme- and deuteroheme-containing cytochromes when grown in the presence of manganese deuteroheme. Versatility in tetrapyrrole utilization by B. ruminicola appears to reflect the ability of the organism to mediate the removal of nonferrous ions and to insert Fe2+ into the tetrapyrrole nucleus. The orgamism also forms functional b-type cytochromes with prosthetic groups other than protoheme.