Dps and DpsL Mediate SurvivalIn VitroandIn Vivoduring the Prolonged Oxidative Stress Response in Bacteroides fragilis

Abstract

Bacteroides fragilis is a Gram-negative anaerobe and member of the human intestinal tract microbiome, where it plays many beneficial roles. However, translocation of the organism to the peritoneal cavity can lead to peritonitis, intra-abdominal abscess formation, bacteremia, and sepsis. During translocation, B. fragilis is exposed to increased oxidative stress from the oxygenated tissues of the peritoneal cavity and the immune response. In order to survive, B. fragilis mounts a robust oxidative stress response consisting of an acute and a prolonged oxidative stress (POST) response. This report demonstrates that the ability to induce high levels of resistance to tert-butyl hydroperoxide (tBOOH) after extended exposure to air can be linked to the POST response. Disk diffusion assays comparing the wild type to a ⌬dps mutant and a ⌬dps ⌬bfr mutant showed greater sensitivity of the mutants to tBOOH after exposure to air, suggesting that Dps and DpsL play a role in the resistance phenotype. Complementation studies with dps or bfr (encoding DpsL) restored tBOOH resistance, suggesting a role for both of these ferritin-family proteins in the response. Additionally, cultures treated with the iron chelator dipyridyl were not killed by tBOOH, indicating Dps and DpsL function by sequestering iron to prevent cellular damage. An in vivo animal model showed that the ⌬dps ⌬bfr mutant was attenuated, indicating that management of iron is important for survival within the abscess. Together, these data demonstrate a role for Dps and DpsL in the POST response which mediates survival in vitro and in vivo. IMPORTANCEB. fragilis is the anaerobe most frequently isolated from extraintestinal opportunistic infections, but there is a paucity of information about the factors that allow this organism to survive outside its normal intestinal environment. This report demonstrates that the iron storage proteins Dps and DpsL protect against oxidative stress and that they contribute to survival both in vitro and in vivo. Additionally, this work demonstrates an important role for the POST response in B. fragilis survival and provides insight into the complex regulation of this response. Bacteroides spp. are members of the normal intestinal microbiome of humans. The intestine is a consistent and favorable environment that provides continuous access to nutrient sources for these strictly anaerobic organisms. Bacteroides spp. play many important roles in maintaining a healthy intestinal tract, such as polysaccharide degradation, protection of the gut epithelia from colonization by pathogenic bacteria, development of the intestinal tract, maturation of the mucosal and systemic immune systems, and transformation of toxic and mutagenic compounds (1-4). However, when the integrity of the intestinal wall is breached due to trauma, abdominal surgery, or diseases such as appendicitis, perforated ulcer, diverticulitis, and colon cancer, translocation of the normal flora into the peritoneal cavity can result in peritonitis and establishment of an intr...

Anaerobic utilization of Fe(III)‐xenosiderophores among Bacteroides species and the distinct assimilation of Fe(III)‐ferrichrome by Bacteroides fragilis within the genus

“…In conclusion, this study shows that Bacteroides species assimilate Fe(III)‐xenosiderophores for growth under anaerobic conditions in vitro. Despite our limited knowledge of iron bound to xenosiderophores assimilation in anaerobes, our findings support previous studies demonstrating that Bacteroides have developed different strategies to deal with the challenges of iron acquisition, genetic regulation and iron‐storage during transitions from anaerobic to aerotolerant metabolism (Betteken, Rocha, & Smith, ; Gauss et al., ; Rocha & Smith, , , ). Moreover, future investigations on the transport and regulatory mechanisms for utilization of catechol siderophores in B. vulgatus associated with colitis will advance our understanding on the role iron acquisition systems play in Bacteroides pathophysiology.…”

The Fumarate Reductase of Bacteroides thetaiotaomicron , unlike That of Escherichia coli , Is Configured so that It Does Not Generate Reactive Oxygen Species

“…Second, while the ROS can inactivate enzymes and impair regular metabolism, they do not generate life-threatening DNA lesions (Fig. 3A), because the OxyR-mediated induction of iron storage proteins defuses the possibility of Fenton chemistry (42). Finally, by using its respiration-linked cytochrome bd oxidase and cytoplasmic rubredoxin:oxygen oxidoreductase, B. thetaiotaomicron presumably can gradually clear oxygen from the local microenvironment, allowing the bacterium to repair its damaged enzymes and to restore its full metabolic capacity.…”

Endogenous superoxide is a key effector of the oxygen sensitivity of a model obligate anaerobe

“…The question remains as to whether these ROS poison obligate anaerobes. Among the bacteria whose oxygen sensitivity has received particular attention are members of the Bacteroidetes (13)(14)(15)(16)(17)(18). These carbohydrate fermenters are among the dominant bacteria in the mammalian gut (19), where they grow alongside E. coli.…”