An Oxidative Pathway for Microbial Utilization of Methylphosphonic Acid as a Phosphate Source

Area of Science:

• Microbiology
• Biochemistry
• Environmental Science

Background:

• Methylphosphonic acid is a key component of marine dissolved organic phosphorus.
• Marine bacteria utilize methylphosphonic acid as a source of inorganic phosphate (Pi) when other sources are scarce.
• The known pathway for methylphosphonic acid conversion to Pi involves carbon-phosphorus lyase, producing methane.

Purpose of the Study:

• To investigate the metabolic fate of methylphosphonic acid in marine bacteria lacking the carbon-phosphorus lyase pathway.
• To identify and characterize novel enzymes involved in methylphosphonic acid catabolism.

Main Methods:

• Genomic analysis of Gimesia maris DSM8797 to identify relevant gene loci.
• Heterologous expression and purification of putative enzymes (GmPhnY* and GmPhnZ1) in E. coli.
• In vitro enzymatic assays using synthetic phosphonates and 31P NMR spectroscopy to determine reaction products.

Main Results:

• Gimesia maris DSM8797 catabolizes methylphosphonic acid via an oxidative pathway, distinct from the carbon-phosphorus lyase route.
• The pathway involves two non-heme Fe(II)-dependent oxygenases, GmPhnY* and GmPhnZ1.
• GmPhnY* converts methylphosphonic acid to hydroxymethylphosphonic acid, which GmPhnZ1 oxidizes to formic acid and Pi.
• This pathway does not process 2-aminoethylphosphonic acid.

Conclusions:

• A new oxidative pathway for methylphosphonic acid breakdown in marine bacteria has been elucidated.
• This pathway provides an alternative source of inorganic phosphate for bacteria lacking the canonical carbon-phosphorus lyase.
• The findings expand our understanding of phosphorus cycling in marine ecosystems.