Microorganisms can influence inorganic phosphate (P i) in pore waters, and thus the saturation state of phosphatic minerals, by accumulating and hydrolyzing intracellular polyphosphate (poly-P). Here we used comparative metatranscriptomics to explore microbial poly-P utilization in marine sediments. Sulfidic marine sediments from methane seeps near Barbados and from the Santa Barbara Basin (SBB) oxygen minimum zone were incubated under oxic and anoxic sulfidic conditions. P i was sequestered under oxic conditions and liberated under anoxic conditions. Transcripts homologous to poly-P kinase type 2 (ppk2) were 6-22 × more abundant in metatranscriptomes from the anoxic incubations, suggesting that reversible poly-P degradation by Ppk2 may be an important metabolic response to anoxia by marine microorganisms. Overall, diverse taxa differentially expressed homologues of genes for poly-P degradation (ppk2 and exopolyphosphatase) under different incubation conditions. Sulfur-oxidizing microorganisms appeared to preferentially express genes for poly-P degradation under anoxic conditions, which may impact phosphorus cycling in a wide range of oxygen-depleted marine settings.
Bibliographical noteFunding Information:
We thank three anonymous reviewers for their contributions that improved this manuscript. This work was supported by a Grant-in-Aid from the University of Minnesota and by National Science Foundation (NSF) grant EAR-1057119 to JB. The Barbados cruise was supported by NSF grant OCE-1031050 to C. Van-Dover and C. Cunningham at Duke University, and the SBB cruise was supported by NSF grant OCE-1230900 to C. Reimers. We acknowledge the Agouron Institute for a generous postdoctoral fellowship to DJ. C. Nguyen and the Minnesota Supercomputing Institute provided computing support and the use of facilities. Special thanks to V. Edgecomb for insightful discussion regarding metatranscriptomics, and to A. Becker, K. Beckman, A. Hague and D. Gohl at the UMGC for assistance and advice with metatranscriptome and amplicon sequencing. We also thank C. Van-Dover and the crew of the R/V Atlantis and ROV Jason (AT 21-02) for assisting with sample collection in Barbados and to the crew of the R/V New Horizon, C. Reimers, and the participants of the UNOLS Early Career Chief Scientist Training Cruise for sample collection in SBB.