Mycobacterium smegmatis does not display functional redundancy in nitrate reductase enzymes

Reduction of nitrate to nitrite in bacteria is an essential step in the nitrogen cycle, catalysed by a variety of nitrate reductase (NR) enzymes. The soil dweller, Mycobacterium smegmatis is able to assimilate nitrate and herein we set out to confirm the genetic basis for this by probing NR activity...

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Bibliographic Details
Published in:PloS one 2021-01, Vol.16 (1), p.e0245745-e0245745
Main Authors: Cardoso, Nicole C, Papadopoulos, Andrea O, Kana, Bavesh D
Format: Article
Language:English
Subjects:
Annotations
Antibiotics
Bacteria
Biology and Life Sciences
Biomedical materials
E coli
Editing
Electron transfer
Enzymes
Eukaryotes
Fixation
Gene expression
Genetic aspects
Genomes
Genotype
Glycerol
Health sciences
Hygromycin
Identification and classification
Kanamycin
Laboratories
Microbiological research
Molybdenum
Mycobacteria
Mycobacterium
Nitrate reductase
Nitrate reduction
Nitrates
Nitrogen
Nucleic acids
Periplasm
Physical Sciences
Plasmids
Prokaryotes
Proteins
Protonmotive force
Reductases
Redundancy
Research and Analysis Methods
Respiratory function
Strains (organisms)
Tuberculosis
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Summary:Reduction of nitrate to nitrite in bacteria is an essential step in the nitrogen cycle, catalysed by a variety of nitrate reductase (NR) enzymes. The soil dweller, Mycobacterium smegmatis is able to assimilate nitrate and herein we set out to confirm the genetic basis for this by probing NR activity in mutants defective for putative nitrate reductase (NR) encoding genes. In addition to the annotated narB and narGHJI, bioinformatics identified three other putative NR-encoding genes: MSMEG_4206, MSMEG_2237 and MSMEG_6816. To assess the relative contribution of each, the corresponding gene loci were deleted using two-step allelic replacement, individually and in combination. The resulting strains were tested for their ability to assimilate nitrate and reduce nitrate under aerobic and anaerobic conditions, using nitrate assimilation and modified Griess assays. We demonstrated that narB, narGHJI, MSMEG_2237 and MSMEG_6816 were individually dispensable for nitrate assimilation and for nitrate reductase activity under aerobic and anaerobic conditions. Only deletion of MSMEG_4206 resulted in significant reduction in nitrate assimilation under aerobic conditions. These data confirm that in M. smegmatis, narB, narGHJI, MSMEG_2237 and MSMEG_6816 are not required for nitrate reduction as MSMEG_4206 serves as the sole assimilatory NR.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0245745