Bacteroides are gram-negative anaerobes and one of the most abundant members the lower GI tract microflora where they play an important role in normal intestinal physiology. Disruption of this commensal relationship has a great impact on human health and disease. Bacteroides spp. are significant opportunistic pathogens causing
infections when the mucosal barrier integrity is disrupted following predisposing conditions such as GI surgery, perforated or gangrenous
appendicitis, perforated ulcer,
diverticulitis,
trauma and
inflammatory bowel diseases. B. fragilis accounts for 60-90 % of all anaerobic
infections despite being a minor component of the genus (<1 % of the flora). Clinical strains of B. fragilis are among the most aerotolerant anaerobes. When shifted from anaerobic to aerobic conditions B. fragilis responds to oxidative stress by inducing the expression of an extensive set of genes involved in protection against
oxygen derived radicals and
iron homeostasis. In Bacteroides, little is known about the
metal/oxidative stress interactions and the mobilization of intra-cellular non-
heme iron during the oxidative stress response has been largely overlooked. Here we present an overview of the work carried out to demonstrate that both
oxygen-detoxifying
enzymes and
iron-storage
proteins are essential for B. fragilis to survive an adverse
oxygen-rich environment. Some species of Bacteroides have acquired multiple homologues of the
iron storage and detoxifying
ferritin-like
proteins but some species contain none. The
proteins found in Bacteroides are classical mammalian H-type non-
heme ferritin (FtnA), non-specific
DNA binding and
starvation protein (Dps) and the newly characterized bacterial Dps-Like miniferritin
protein. The full contribution of
ferritin-like
proteins to pathophysiology of commensal and opportunistic pathogen Bacteroides spp. still remains to be elucidated.