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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Bioenergy Research » Research » Publications at this Location » Publication #325132

Research Project: Understanding the Role of Commensal Anaerobic Bacteria in Odor, Emissions, and Antibiotic Resistance from Stored Livestock Manure

Location: Bioenergy Research

Title: Pirin-like proteins are regulated by oxidative stress and iron in bacteroides fragilis and involved in the modulation of central energy metabolism and metronidazole susceptibility

Author
item ROCHA, EDSON - East Carolina University
item GOUGH, ANDREA - East Carolina University
item O Bryan, Patricia
item Whitehead, Terence
item SMITH, C. JEFFREY - East Carolina University

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2016
Publication Date: 6/16/2016
Citation: Rocha, E.R., Gough, A.M., O Bryan, P.J., Whitehead, T.R., Smith, C. 2016. Pirin-like proteins are regulated by oxidative stress and iron in bacteroides fragilis and involved in the modulation of central energy metabolism and metronidazole susceptibility [abstract]. American Society for Microbiology.

Interpretive Summary:

Technical Abstract: Bacteroides fragilis is the most frequent anaerobe isolated from human infections. Clinical isolates of B. fragilis are among the highest aerotolerant anaerobic bacteria. The oxidative stress response (OSR) in B. fragilis induces an array of genes enabling them to survive prolonged oxygen exposure in the aerobic extra-intestinal tissues until abscess formation provides a favourable anaerobic infectious environment. Among the OSR genes, two pirin-like homologues, Pirin 1 (Pir1) and Pirin 2 (Pir2) were found to be induced by oxygen exposure and iron availability determined by whole genome transcriptional analysis and real-time RT-PCR. Pirin-like proteins are iron-containing proteins of the cupin superfamily present in all kingdoms ranging from archae to humans. Real time RT-PCR also confirmed the up-regulation of the genes for pir1 (7.2-fold) and pir2 (9.5-fold) following exposure to oxygen compared to anaerobic culture controls. Under anaerobic low-iron conditions, pir1 and pir2 genes were induced approximately 7.6-fold and 9.3-fold respectively compared to the levels under iron-replete conditions in a Fur-independent manner. To investigate the role of Pir1 and Pir2 in B. fragilis, we have used bacterial two-hybrid system to show that Pir1 and Pir2 interacts with pyruvate:ferridoxin oxidoreductase (PFOR) and alcohol dehydrogenase (ADH). This suggests that pirin-like proteins possibly play a role in response to oxidative stress by interacting with enzymes involved in B. fragilis central energy metabolism. The B. fragilis strains constitutively expressing Pir1 and Pir2 had a strong reduction in lactate levels and increase in acetate and ethanol levels compared to parent strain under anaerobic conditions. Moreover, constitutively expressing Pir1 and Pir2 strains were more sensitive to the antibiotic metronidazole compared to parent strain possibly due to the protein-protein interactions between the PFOR and Pir-like proteins. Taken together, these findings show that there is a coordinate regulation of pirin proteins during OSR and iron limitation in B. fragilis that affects central energy metabolic fermentative pathways and antibiotic resistance.