Metatranscriptomic insights into polyphosphate metabolism in marine sediments

Area of Science:

• Microbial Ecology
• Biogeochemistry
• Marine Science

Background:

• Microorganisms influence marine inorganic phosphate (Pi) and phosphatic mineral saturation through polyphosphate (poly-P) metabolism.
• Polyphosphate serves as an intracellular energy reserve and a source/sink for Pi.

Purpose of the Study:

• To investigate microbial poly-P utilization in marine sediments using comparative metatranscriptomics.
• To understand the microbial response to varying oxygen and sulfide conditions concerning poly-P metabolism.

Main Methods:

• Comparative metatranscriptomics of marine sediments from methane seeps and an oxygen minimum zone.
• Incubation of sediment samples under oxic and anoxic sulfidic conditions.
• Analysis of gene expression for poly-P metabolism, including poly-P kinase type 2 (ppk2) and exopolyphosphatase.

Main Results:

• Inorganic phosphate (Pi) was sequestered under oxic conditions and liberated under anoxic conditions.
• Transcripts for poly-P kinase type 2 (ppk2) were significantly more abundant in anoxic incubations (6-22x).
• Diverse microbial taxa differentially expressed genes for poly-P degradation (ppk2, exopolyphosphatase) based on incubation conditions.

Conclusions:

• Reversible poly-P degradation by Ppk2 is a key metabolic response to anoxia in marine microorganisms.
• Sulfur-oxidizing microorganisms preferentially express poly-P degradation genes under anoxia.
• Microbial poly-P utilization plays a significant role in phosphorus cycling in oxygen-depleted marine environments.