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Bacterial variations on the methionine salvage pathway
Agnieszka Sekowska1, Valérie Dénervaud, Hiroki Ashida
1HKU-Pasteur Research Centre, 8, Sassoon Road, Pokfulam, Hong Kong, SAR Hong Kong. sekowska@pasteur.fr
BMC Microbiology
|April 23, 2004
Summary
This study uncovers methionine salvage pathways in bacteria like Klebsiella pneumoniae and Pseudomonas aeruginosa, revealing enzyme recruitment and oxygen dependence. These findings advance our understanding of essential nutrient recycling in diverse microbial environments.
Area of Science:
- Microbiology
- Biochemistry
- Genomics
Background:
- S-adenosylmethionine's thiomethyl group is typically recycled as methionine from methylthioadenosine.
- While the methionine salvage pathway is known in Bacillus subtilis, alternative degradation routes exist across organisms.
- Methylthioadenosine metabolism varies significantly between bacterial species.
Purpose of the Study:
- To propose and investigate methionine salvage pathways in Klebsiella pneumoniae, Leptospira interrogans, Thermoanaerobacter tengcongensis, and Xylella fastidiosa using in silico genomic analysis.
- To experimentally validate proposed pathways in Bacillus subtilis and Pseudomonas aeruginosa mutants.
- To identify the enzymes involved and their evolutionary origins.
Main Methods:
- Genome-wide in silico analysis to predict pathway components.
- Experimental studies using bacterial mutants (B. subtilis, P. aeruginosa).
- Enzyme characterization and analysis of reaction mechanisms.
Main Results:
- Proposed methionine salvage pathways for K. pneumoniae, L. interrogans, T. tengcongensis, and X. fastidiosa.
- Experimental confirmation of the pathway in P. aeruginosa, demonstrating its functionality.
- Identified key enzymes including MtnA (methylthioribose-1-phosphate isomerase) and mtnB (methylthioribulose-1-phosphate dehydratase), with variations in enolase-phosphatase activity across species.
- Observed oxygen-dependent aci-reductone dioxygenase activity producing ketomethylthiobutyrate, a methionine precursor.
- Noted potential carbon monoxide production by aci-reductone dioxygenase in B. subtilis.
Conclusions:
- A functional methionine salvage pathway was experimentally verified in P. aeruginosa for the first time.
- Methionine salvage pathways are widespread in Bacteria and Eukarya, utilizing diverse enzymes, including those related to translation initiation factors and RuBisCO.
- Oxygen availability significantly influences pathway activity, highlighting the role of ecological niches.
- Further research is needed to elucidate anaerobic pathways, particularly in organisms like T. tengcongensis.