Who Is the Rock Miner and Who Is the Hunter? The Use of Heavy Oxygen Labeled Phosphate (P18O4) to Differentiate between C and P Fluxes in a Benzene-Degrading Consortium

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  • Phosphorus availability and cycling in microbial
    communities is a key determinant of bacterial activity. However,
    identifying organisms critical to P cycling in complex biodegrading
    consortia has proven elusive. Here we assess a new DNA stable
    isotope probing (SIP) technique using heavy oxygen-labeled
    phosphate (P18O4) and its effectiveness in pure cultures and a
    nitrate-reducing benzene-degrading consortium. First, we successfully labeled pure cultures of Gram-positive Micrococcus luteus and
    Gram-negative Bradyrhizobium elkanii and separated isotopically
    light and heavy DNA in pure cultures using centrifugal analyses.
    Second, using high-throughput amplicon sequencing of 16S rRNA
    genes to characterize active bacterial taxa (13C-labeled), we found
    taxa like Betaproteobacteria were key in denitrifying benzene
    degradation and that other degrading (nonhydrocarbon) inactive taxa (P18O4-labeled) like Staphylococcus and Corynebacterium
    may promote degradation through production of secondary metabolites (i.e., “helper” or “rock miner” bacteria). Overall, we
    successfully separated active and inactive taxa in contaminated soils, demonstrating the utility of P18O4-DNA SIP for identifying
    actively growing bacterial taxa. We also identified potential “miner” bacteria that choreograph hydrocarbon degradation by other
    microbes (i.e., the “hunters”) without directly degrading contaminants themselves. Thus, while several taxa degrade benzene
    under denitrifying conditions, microbial benzene degradation may be enhanced by both direct degraders and miner bacteria

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    Article (Published)
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    Attribution-NonCommercial 4.0 International