title: Mechanisms of direct inhibition of the respiratory sulfate-reduction pathway by (per)chlorate and nitrate.
abstract: We investigated perchlorate (ClO(4)(-)) and chlorate (ClO(3)(-)) (collectively (per)chlorate) in comparison with nitrate as potential inhibitors of sulfide (H(2)S) production by mesophilic sulfate-reducing microorganisms (SRMs). We demonstrate the specificity and potency of (per)chlorate as direct SRM inhibitors in both pure cultures and undefined sulfidogenic communities. We demonstrate that (per)chlorate and nitrate are antagonistic inhibitors and resistance is cross-inducible implying that these compounds share at least one common mechanism of resistance. Using tagged-transposon pools we identified genes responsible for sensitivity and resistance in Desulfovibrio alaskensis G20. We found that mutants in Dde_2702 (Rex), a repressor of the central sulfate-reduction pathway were resistant to both (per)chlorate and nitrate. In general, Rex derepresses its regulon in response to increasing intracellular NADH:NAD(+) ratios. In cells in which respiratory sulfate reduction is inhibited, NADH:NAD(+) ratios should increase leading to derepression of the sulfate-reduction pathway. In support of this, in (per)chlorate or nitrate-stressed wild-type G20 we observed higher NADH:NAD(+) ratios, increased transcripts and increased peptide counts for genes in the core Rex regulon. We conclude that one mode of (per)chlorate and nitrate toxicity is as direct inhibitors of the central sulfate-reduction pathway. Our results demonstrate that (per)chlorate are more potent inhibitors than nitrate in both pure cultures and communities, implying that they represent an attractive alternative for controlling sulfidogenesis in industrial ecosystems. Of these, perchlorate offers better application logistics because of its inhibitory potency, solubility, relative chemical stability, low affinity for mineral cations and high mobility in environmental systems.
authors.affiliation: Energy Biosciences Institute, UC Berkeley, Berkeley, CA, USA.
authors.forename: Hans K
authors.initials: HK
authors.lastname: Carlson
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors.forename: Jennifer V
authors.initials: JV
authors.lastname: Kuehl
authors.affiliation: Department of Plant and Microbial Biology, UC Berkeley, Berkeley, CA, USA.
authors.forename: Amrita B
authors.initials: AB
authors.lastname: Hazra
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Justice
authors.affiliation: Department of Plant and Microbial Biology, UC Berkeley, Berkeley, CA, USA.
authors.forename: Magdalena K
authors.initials: MK
authors.lastname: Stoeva
authors.affiliation: Department of Bioengineering, UC Berkeley, Berkeley, CA, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Sczesnak
authors.affiliation: Energy Biosciences Institute, UC Berkeley, Berkeley, CA, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Mullan
authors.affiliation: QB3/Chemistry Mass Spectrometry Facility, UC Berkeley, Berkeley, CA, USA.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Iavarone
authors.affiliation: Department of Plant and Microbial Biology, UC Berkeley, Berkeley, CA, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Engelbrektson
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors.forename: Morgan N
authors.initials: MN
authors.lastname: Price
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Deutschbauer
authors.affiliation: 1] Physical Biosciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA [2] Department of Bioengineering, UC Berkeley, Berkeley, CA, USA.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Arkin
authors.affiliation: 1] Energy Biosciences Institute, UC Berkeley, Berkeley, CA, USA [2] Department of Plant and Microbial Biology, UC Berkeley, Berkeley, CA, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Coates
mesh_terms: D002704:Chlorates / Q000737:chemistry*; D004251:DNA Transposable Elements; D003901:Desulfovibrio / Q000378:metabolism; D017753:Ecosystem; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D023281:Genomics; D009154:Mutation; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D010472:Perchlorates / Q000737:chemistry*; D016133:Polymerase Chain Reaction; D040901:Proteomics; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D013431:Sulfates / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry; D016999:Sulfur-Reducing Bacteria / Q000378:metabolism
chemical_list: D002704:Chlorates; D004251:DNA Transposable Elements; D009566:Nitrates; D010472:Perchlorates; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D013440:Sulfides; C494474:perchlorate