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ROS-based lethality of Caenorhabditis elegans mitochondrial electron transport mutants grown on Escherichia coli siderophore iron release mutants.

ABSTRACT: Caenorhabditis elegans consumes bacteria, which can supply essential vitamins and cofactors, especially for mitochondrial functions that have a bacterial ancestry. Therefore, we screened the Keio Escherichia coli knockout library for mutations that induce the C. elegans hsp-6 mitochondrial damage response gene, and identified 45 E. coli mutations that induce hsp-6::gfp We tested whether any of these E. coli mutations that stress the C. elegans mitochondrion genetically interact with C. elegans mutations in mitochondrial functions. Surprisingly, 4 E. coli mutations that disrupt the import or removal of iron from the bacterial siderophore enterobactin were lethal in combination with a collection of C. elegans mutations that disrupt particular iron-sulfur proteins of the electron transport chain. Bacterial mutations that fail to synthesize enterobactin are not synthetic lethal with these C. elegans mitochondrial mutants; it is the enterobactin-iron complex that is lethal in combination with the C. elegans mitochondrial mutations. Antioxidants suppress this inviability, suggesting that reactive oxygen species (ROS) are produced by the mutant mitochondria in combination with the bacterial enterobactin-iron complex.

SUBMITTER: Govindan JA

PROVIDER: S-EPMC6815122 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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ROS-based lethality of Caenorhabditis elegans mitochondrial electron transport mutants grown on Escherichia coli siderophore iron release mutants.

Govindan J Amaranath JA Jayamani Elamparithi E Ruvkun Gary G

Proceedings of the National Academy of Sciences of the United States of America 20191007 43

Caenorhabditis elegans consumes bacteria, which can supply essential vitamins and cofactors, especially for mitochondrial functions that have a bacterial ancestry. Therefore, we screened the Keio Escherichia coli knockout library for mutations that induce the C. elegans hsp-6 mitochondrial damage response gene, and identified 45 E. coli mutations that induce hsp-6::gfp We tested whether any of these E. coli mutations that stress the C. elegans mit ...[more]

PMID: 31591219

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Project description:Prior studies have shown that disruption of mitochondrial electron transport chain (ETC) function in the nematode Caenorhabditis elegans can result in life extension. Counter to these findings, many mutations that disrupt ETC function in humans are known to be pathologically life-shortening. In this study, we have undertaken the first formal investigation of the role of partial mitochondrial ETC inhibition and its contribution to the life-extension phenotype of C. elegans. We have developed a novel RNA interference (RNAi) dilution strategy to incrementally reduce the expression level of five genes encoding mitochondrial proteins in C. elegans: atp-3, nuo-2, isp-1, cco-1, and frataxin (frh-1). We observed that each RNAi treatment led to marked alterations in multiple ETC components. Using this dilution technique, we observed a consistent, three-phase lifespan response to increasingly greater inhibition by RNAi: at low levels of inhibition, there was no response, then as inhibition increased, lifespan responded by monotonically lengthening. Finally, at the highest levels of RNAi inhibition, lifespan began to shorten. Indirect measurements of whole-animal oxidative stress showed no correlation with life extension. Instead, larval development, fertility, and adult size all became coordinately affected at the same point at which lifespan began to increase. We show that a specific signal, initiated during the L3/L4 larval stage of development, is sufficient for initiating mitochondrial dysfunction-dependent life extension in C. elegans. This stage of development is characterized by the last somatic cell divisions normally undertaken by C. elegans and also by massive mitochondrial DNA expansion. The coordinate effects of mitochondrial dysfunction on several cell cycle-dependent phenotypes, coupled with recent findings directly linking cell cycle progression with mitochondrial activity in C. elegans, lead us to propose that cell cycle checkpoint control plays a key role in specifying longevity of mitochondrial mutants.

Project description:BackgroundAcetate is the major source of methane in nature. The majority of investigations have focused on acetotrophic methanogens for which energy-conserving electron transport is dependent on the production and consumption of H₂ as an intermediate, although the great majority of acetotrophs are unable to metabolize H₂. The presence of cytochrome c and a complex (Ma-Rnf) homologous to the Rnf (Rhodobacter nitrogen fixation) complexes distributed in the domain Bacteria distinguishes non-H₂-utilizing Methanosarcina acetivorans from H₂-utilizing species suggesting fundamentally different electron transport pathways. Thus, the membrane-bound electron transport chain of acetate-grown M. acetivorans was investigated to advance a more complete understanding of acetotrophic methanogens.ResultsA component of the CO dehydrogenase/acetyl-CoA synthase (CdhAE) was partially purified and shown to reduce a ferredoxin purified using an assay coupling reduction of the ferredoxin to oxidation of CdhAE. Mass spectrometry analysis of the ferredoxin identified the encoding gene among annotations for nine ferredoxins encoded in the genome. Reduction of purified membranes from acetate-grown cells with ferredoxin lead to reduction of membrane-associated multi-heme cytochrome c that was re-oxidized by the addition of either the heterodisulfide of coenzyme M and coenzyme B (CoM-S-S-CoB) or 2-hydoxyphenazine, the soluble analog of methanophenazine (MP). Reduced 2-hydoxyphenazine was re-oxidized by membranes that was dependent on addition of CoM-S-S-CoB. A genomic analysis of Methanosarcina thermophila, a non-H2-utilizing acetotrophic methanogen, identified genes homologous to cytochrome c and the Ma-Rnf complex of M. acetivorans.ConclusionsThe results support roles for ferredoxin, cytochrome c and MP in the energy-conserving electron transport pathway of non-H₂-utilizing acetotrophic methanogens. This is the first report of involvement of a cytochrome c in acetotrophic methanogenesis. The results suggest that diverse acetotrophic Methanosarcina species have evolved diverse membrane-bound electron transport pathways leading from ferredoxin and culminating with MP donating electrons to the heterodisulfide reductase (HdrDE) for reduction of CoM-S-S-CoB.

Dataset Information

ROS-based lethality of Caenorhabditis elegans mitochondrial electron transport mutants grown on Escherichia coli siderophore iron release mutants.

Publications

ROS-based lethality of <i>Caenorhabditis elegans</i> mitochondrial electron transport mutants grown on <i>Escherichia coli</i> siderophore iron release mutants.

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