Research ArticleECOLOGY

Life on the thermodynamic edge: Respiratory growth of an acetotrophic methanogen

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Science Advances  21 Aug 2019:
Vol. 5, no. 8, eaaw9059
DOI: 10.1126/sciadv.aaw9059
  • Fig. 1 Time course of growth parameters for acetate-grown cultures of M. acetivorans with and without supplements.

    (A) Protein. (B) Acetate. (C) Methane. (D) Fe(II). ●, without supplements; ○, with 0.2 mM anthraquinone-2,6-disulfonate (AQDS); ▲, with 20 mM ferrihydrite; Δ, with 0.2 mM AQDS and 20 mM ferrihydrite; ■, uninoculated media with 20 mM ferrihydrite. Values are the mean of three biological replicates. Error bars represent the SD.

  • Fig. 2 Cell counts with time for unamended cultures and cultures of M. acetivorans amended with ferrihydrite and AQDS.

    Bars are the mean of three biological replicates, in which the SD is shown by error bars.

  • Fig. 3 Production of protein and Fe(II) at the end of growth correlated with increasing concentrations of ferrihydrite in the media that contained 0.2 mM AQDS.

    Bars are the mean of three biological replicates, in which the SD is shown by error bars.

  • Fig. 4 The ATP/ADP ratio of acetate-grown M. acetivorans sampled at midgrowth.

    (A) No additions. (B) Ferrihydrite. (C) Ferrihydrite and AQDS. Bars are the mean of three biological replicates, in which the SD is shown by error bars.

  • Fig. 5 The aceticlastic pathway proposed for growth of M. acetivorans in the presence of ferrihydrite.

    The stoichiometry shown is arbitrary. The respiratory metabolism of acetate is shown in bolded and italicized font. Atp, ATP synthase; Rnf, homolog of the Rhodobacter nitrogen fixation complex; Fdx, ferredoxin; Cyt c, multiheme cytochrome c; MP, methanophenazine; HdrED, membrane-bound heterodisulfide reductase; H4SPT, tetrahydrosarcinapterin; HSCoM, coenzyme M; HSCoB, coenzyme B; MF, methanofuran; HdrA2B2C2, cytoplasmic heterodisulfide reductase; F420, coenzyme F420; Mtr, CH3-H4SPT:HSCoM methyltransferase; Mrp, multisubunit sodium/proton antiporter.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/8/eaaw9059/DC1

    Fig. S1. Growth parameters of subcultures amended with both AQDS and ferrihydrite.

    Fig. S2. The XRD spectra.

    Fig. S3. Alternate pathways of F420H2 reoxidation independent of methanogenesis.

    Table S1. Culture parameters shown in Fig. 2.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Growth parameters of subcultures amended with both AQDS and ferrihydrite.
    • Fig. S2. The XRD spectra.
    • Fig. S3. Alternate pathways of F420H2 reoxidation independent of methanogenesis.
    • Table S1. Culture parameters shown in Fig. 2.

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