Nitroreductases of bacterial origin in Giardia lamblia: Potential role in detoxification of xenobiotics

Our study is focused on a family of nitroreductases identified in the genome of the intestinal protozoanGiardia lamblia, a causative agent of persistent diarrhea in humans and mammals. The corresponding genes have most likely been acquired by lateral transfer from anaerobic bacteria or archaebacterial, and the functions of the gene products are still unclear. Now, we found that these enzymes have a potential role in detoxification of xenobiotics produced by microorganisms living in concurrence inside the intestinal habitat. AbstractThe anaerobic parasiteGiardia lamblia, causative agent of persistent diarrhea, contains a family of nitroreductase genes most likely acquired by lateral transfer from anaerobic bacteria or archaebacteria. Two of these nitroreductases, containing a ferredoxin domain at their N ‐terminus, NR1, and NR2, have been characterized previously. Here, we present the characterization of a third member of this family, NR3. In functional assays, recombinant NR1 and NR3 reduced quinones like menadione and the antibiotic tetracycline, and—to much lesser extents—the nitro compound dinitrotoluene. Conversely, recombinant NR2 had no activity on tetracycline.Escherichia coli expressing NR3 were less susceptible to tetracycline, but more susceptible to the nitro compound metronidazole under semi ‐aerobic growth conditions.G.  lamblia overexpressing NR1 and NR3, but not lines overexpressing NR2, are more susceptible to the nitro drug nitazoxanide. These findin...

Source: MicrobiologyOpen - July 24, 2019 Category: Microbiology Authors: Joachim M üller, Norbert Müller Tags: ORIGINAL ARTICLE Source Type: research