The Uros and Yifb Genes Conserved among Tetrapyrrole Synthesizing-Deficient Bacteroidales Are Involved in Bacteroides Fragilis Heme Assimilation and Survival in Experimental Intra-abdominal Infection and Intestinal Colonization

The human intestinal anaerobic commensal and opportunistic pathogen Bacteroides fragilis does not synthesize the tetrapyrrole protoporphyrin IX in order to form heme that is required for growth stimulation and survival in vivo . Consequently, B. fragilis acquires essential heme from host tissues during extraintestinal infection. The absence of several genes necessary for de novo heme biosynthesis is a common characteristic of many anaerobic bacteria; however, the uroS gene, encoding a uroporphyrinogen III synthase for an early step of heme biosynthesis, is conserved among the heme-requiring Bacteroidales that inhabit the mammalian gastrointestinal tract.