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- Invited Review - |
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Identification of the mechanism for dehalorespiration of monofluoroacetate in the phylum Synergistota |
Lex E. X. Leong1 
, Stuart E. Denman1,*
, Seungha Kang1,2
, Stanislas Mondot3
, Philip Hugenholtz4
, Chris S. McSweeney1
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1CSIRO Agriculture and Food, St Lucia 4067, Queensland Australia
2Current address: The University of Queensland Frazer Institute, Faculty of Medicine, University of Queensland, Brisbane, Queensland 4102, Australia
3Micalis Institute, INRA, AgroParisTech, University Paris-Saclay, 78350 Jouy-en- Josas, France
4Australian Centre for Ecogenomics, School of Chemistry and Molecular Bioscience, the University of Queensland, St Lucia, 4072 Queensland Australia |
Correspondence:
Stuart E. Denman, Tel: +61-07-32142273, Email: stuart.denman@csiro.au
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Received: 7 September 2023 • Revised: 20 October 2023 • Accepted: 26 December 2023 |
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| Abstract |
Objective
Monofluoroacetate (MFA) is a potent toxin that blocks ATP production via the Krebs cycle and causes acute toxicity in ruminants consuming MFA-containing plants. The rumen bacterium, Cloacibacillus porcorum strain MFA1 belongs to the phylum Synergistota and can produce fluoride and acetate from MFA as the end-products of dehalorespiration. The aim of this study was to identify the genomic basis for the metabolism of MFA by this bacterium.
Methods
A draft genome sequence for C. porcorum strain MFA1 was assembled and quantitative transcriptomic analysis was performed thus highlighting a candidate operon encoding four proteins that are responsible for the carbon-fluorine bond cleavage. Comparative genome analysis of this operon was undertaken with three other species of closely related Synergistota bacteria.
Results
Two of the genes in this operon are related to the substrate-binding components of the glycine reductase protein B (GrdB) complex. Glycine shares a similar structure to MFA suggesting a role for these proteins in binding MFA. The remaining two genes in the operon, an antiporter family protein and an oxidoreductase belonging to the radical S-adenosyl methionine superfamily, are hypothesised to transport and activate the GrdB-like protein respectively. Similar operons were identified in a small number of other Synergistota bacteria including type strains of Cloacibacillus porcorum, C. evryensis, and Pyramidobacter piscolens, suggesting lateral transfer of the operon as these genera belong to separate families. We confirmed that all three species can degrade MFA, however, substrate degradation in P. piscolens was notably reduced compared to Cloacibacillus isolates possibly reflecting the loss of the oxidoreductase and antiporter in the P. piscolens operon.
Conclusion
Identification of this unusual anaerobic fluoroacetate metabolism extends the known substrates for dehalorespiration and indicates the potential for substrate plasticity in amino acid-reducing enzymes to include xenobiotics. |
| Keywords:
Cloacibacillus; Dehalorespiration; Monofluoroacetate; Pyramidobacter; Rumen; Synergistota |
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