Research ArticleECOLOGY

Microbial dormancy in the marine subsurface: Global endospore abundance and response to burial

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Science Advances  20 Feb 2019:
Vol. 5, no. 2, eaav1024
DOI: 10.1126/sciadv.aav1024
  • Fig. 1 Distribution of vegetative cells and endospores versus depth.

    Concentrations of (A) vegetative cells and (B) endospores and (C) ratio of endospores to vegetative cells versus sediment depth in samples from various Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) expeditions and national research cruises (cf. table S1). Cell concentrations are based on 16S rRNA gene targets quantified using dPCR data or on cell enumeration via flow cytometry (M84/1 and POS-450) and endospore concentrations on the diagnostic biomarker DPA. The solid regression line in (A) is log cells = 7.319 − 1.301 log depth (R2 = 0.519, P < 0.001, n = 267) from this study, and the dashed line is the regression line from the global estimate of the marine subseafloor biosphere (4): log cells = 8.05 − 0.68 log depth (R2 = 0.70, n = 2037). The regression line in (B) is log endospores = 6.039 − 0.228 log depth (R2 = 0.136, P < 0.001, n = 220). Samples with DPA concentration below our current detection limit (D.L.) are shown as empty circles. These data are not included in the regression. The regression line in (C) is log (endospores/cells) = −1.636 + 1.164 log depth {R2 = 0.577, P < 0.001, n = 199; n < 220 [number plotted in (B)] because cell concentration data are not available for all samples in which endospores were detected}.

  • Fig. 2 Endospore response to burial and aging.

    (A) Endospore concentration versus sediment age in samples from various ODP and IODP expeditions and national research cruises (cf. table S1). The segmented regression line (R2 = 0.656, P < 0.0001, n = 166, solid line) in (A) is composed of a first section (age < 14,266 years) with log endospores = 7.515 − 0.450 log age and a second section (age > 14,226 years) with log endospores = 5.993 − 0.084 log age. The lower number of samples in comparison to Fig. 1B is because sediment age data were not available for all sites. (B) Lines represent temperature-dependent decimal reduction values for three groups of increasingly resistant endospores investigated in thermal inactivation experiments (38). They denote the time needed to reduce the endospore population by one order of magnitude at a given temperature. Blue dots indicate depth and age of samples analyzed in this study. Equivalence of depth and temperature axis is obtained by applying a geothermal gradient of 30°C/km.

  • Table 1 Estimates of endospore abundance and biomass.

    Summary of vegetative cell and endospore abundance for the top kilometer of subseafloor sediment based on the three modeling approaches performed. Biomass data are calculated from DPA abundance in the case of endospores and from cell abundance in the case of vegetative cells.

    Modeling approachData usedEndospore populationEndospore biomass
    (Pg C)
    Vegetative cell
    population
    Vegetative cell
    biomass (Pg C)
    Average sediment depth
    calculation
    Global correlation of
    endospore
    concentration vs.
    depth (this study)
    8.2 × 1028151.3 × 10291.8
    Single-site
    parameterization of
    endospore
    concentration
    Endospore
    concentration vs.
    depth at single sites
    (this study)
    2.5 × 10284.6
    Vegetative cell to
    endospore conversion
    Global correlation of
    endospore/cell ratio
    vs. depth (this study).
    Modeled global
    abundance of
    vegetative cells vs.
    depth (2)
    1.9 × 1029358.5 × 10281.2

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/2/eaav1024/DC1

    Section S1. Assessment of potential preservation effects of DPA

    Section S2. Supplementary materials and methods

    Fig. S1. Relationship between endospore and TOC concentrations in the analyzed samples.

    Fig. S2. Location of sites analyzed in the present study.

    Fig. S3. Endospore concentration over depth in four selected sites.

    Fig. S4. Linear regression of the parameters log(b) and m with POC concentration.

    Table S1. Overview of sites analyzed for endospore abundance.

    Table S2. Parameters tested for their correlation to endospore abundance at 1 mbsf (b) and decrease rate with depth (m).

    References (5981)

  • Supplementary Materials

    This PDF file includes:

    • Section S1. Assessment of potential preservation effects of DPA
    • Section S2. Supplementary materials and methods
    • Fig. S1. Relationship between endospore and TOC concentrations in the analyzed samples.
    • Fig. S2. Location of sites analyzed in the present study.
    • Fig. S3. Endospore concentration over depth in four selected sites.
    • Fig. S4. Linear regression of the parameters log(b) and m with POC concentration.
    • Table S1. Overview of sites analyzed for endospore abundance.
    • Table S2. Parameters tested for their correlation to endospore abundance at 1 mbsf (b) and decrease rate with depth (m).
    • References (5981)

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