title: The Redox Cofactor F420Protects Mycobacteria from Diverse Antimicrobial Compounds and Mediates a Reductive Detoxification System.
abstract: A defining feature of mycobacterial redox metabolism is the use of an unusual deazaflavin cofactor, F420This cofactor enhances the persistence of environmental and pathogenic mycobacteria, including after antimicrobial treatment, although the molecular basis for this remains to be understood. In this work, we explored our hypothesis that F420enhances persistence by serving as a cofactor in antimicrobial-detoxifying enzymes. To test this, we performed a series of phenotypic, biochemical, and analytical chemistry studies in relation to the model soil bacteriumMycobacterium smegmatisMutant strains unable to synthesize or reduce F420were found to be more susceptible to a wide range of antibiotic and xenobiotic compounds. Compounds from three classes of antimicrobial compounds traditionally resisted by mycobacteria inhibited the growth of F420mutant strains at subnanomolar concentrations, namely, furanocoumarins (e.g., methoxsalen), arylmethanes (e.g., malachite green), and quinone analogues (e.g., menadione). We demonstrated that promiscuous F420H2-dependent reductases directly reduce these compounds by a mechanism consistent with hydride transfer. Moreover,M. smegmatisstrains unable to make F420H2lost the capacity to reduce and detoxify representatives of the furanocoumarin and arylmethane compound classes in whole-cell assays. In contrast, mutant strains were only slightly more susceptible to clinical antimycobacterials, and this appeared to be due to indirect effects of F420loss of function (e.g., redox imbalance) rather than loss of a detoxification system. Together, these data show that F420enhances antimicrobial resistance in mycobacteria and suggest that one function of the F420H2-dependent reductases is to broaden the range of natural products that mycobacteria and possibly other environmental actinobacteria can reductively detoxify.IMPORTANCEThis study reveals that a unique microbial cofactor, F420, is critical for antimicrobial resistance in the environmental actinobacteriumMycobacterium smegmatisWe show that a superfamily of redox enzymes, the F420H2-dependent reductases, can reduce diverse antimicrobialsin vitroandin vivoM. smegmatisstrains unable to make or reduce F420become sensitive to inhibition by these antimicrobial compounds. This suggests that mycobacteria have harnessed the unique properties of F420to reduce structurally diverse antimicrobials as part of the antibiotic arms race. The F420H2-dependent reductases that facilitate this process represent a new class of antimicrobial-detoxifying enzymes with potential applications in bioremediation and biocatalysis.
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.|Australian National University, Research School of Chemistry, Acton, ACT, Australia.
authors.forename: Thanavit
authors.initials: T
authors.lastname: Jirapanjawat
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.|Australian National University, Research School of Chemistry, Acton, ACT, Australia.
authors.forename: Blair
authors.initials: B
authors.lastname: Ney
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Taylor
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Warden
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.|Australian National University, Research School of Chemistry, Acton, ACT, Australia.
authors.forename: Shahana
authors.initials: S
authors.lastname: Afroze
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.
authors.forename: Robyn J
authors.initials: RJ
authors.lastname: Russell
authors.affiliation: Australian National University, Research School of Chemistry, Acton, ACT, Australia.
authors.forename: Brendon M
authors.initials: BM
authors.lastname: Lee
authors.affiliation: Australian National University, Research School of Chemistry, Acton, ACT, Australia.
authors.forename: Colin J
authors.initials: CJ
authors.lastname: Jackson
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia.
authors.forename: John G
authors.initials: JG
authors.lastname: Oakeshott
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia chris.greening@monash.edu gunjan.pandey@csiro.au.
authors.forename: Gunjan
authors.initials: G
authors.lastname: Pandey
authors.affiliation: The Commonwealth Scientific and Industrial Research Organisation, Land and Water, Acton, ACT, Australia chris.greening@monash.edu gunjan.pandey@csiro.au.
authors.forename: Chris
authors.initials: C
authors.lastname: Greening