Discovering Polyphosphate and Polyhydroxyalkanoate-Accumulating Organisms Across Ecosystems: Phenotype-Targeted...

Area of Science:

• Microbiology
• Environmental Science
• Biotechnology

Background:

• Microbial biopolymers like polyphosphate (polyP) and polyhydroxyalkanoates (PHA) are crucial for adaptation.
• Polyphosphate-accumulating organisms (PAOs) metabolically link polyP and PHA, enabling enhanced biological phosphorus removal (EBPR).
• The prevalence and ecological roles of PHA-PAOs outside of EBPR are largely unknown due to detection limitations.

Purpose of the Study:

• To develop and validate a novel method for detecting, quantifying, and characterizing PHA-PAOs.
• To investigate the presence and diversity of PHA-PAOs in environmental samples, including EBPR systems and maize rhizospheres.
• To explore the potential functions of newly identified PHA-PAOs in plant-growth promotion and nutrient cycling.

Main Methods:

• Developed a phenotype-targeted approach combining triple-stained fluorescence-activated cell sorting with 16S rRNA gene sequencing (TriFlow-Seq).
• Validated TriFlow-Seq using fluorescence imaging and single-cell Raman spectroscopy.
• Applied TriFlow-Seq to activated sludge from EBPR systems and samples from maize rhizosphere.

Main Results:

• TriFlow-Seq successfully identified known PAOs (e.g., *Candidatus* Phosphoribacter, *Tetrasphaera*, *Ca.* Accumulibacter) and discovered novel PHA-PAOs in Rhodobacteraceae.
• The method revealed diverse PHA-PAOs, including *Pseudomonas*, *Halomonas*, and *Nannocystis*, in the maize rhizosphere.
• These rhizosphere PHA-PAOs are implicated in plant-growth-promoting activities like phosphate solubilization and phytohormone production.

Conclusions:

• The TriFlow-Seq method provides a powerful tool for investigating PHA-PAO ecology.
• PHA-PAOs are prevalent in diverse environments, including agricultural soils, and play roles beyond EBPR.
• Biopolymer costorage by PHA-PAOs may significantly influence rhizosphere dynamics and plant health, with patterns varying by plant genotype.