April Z. Gu

Polyphosphate (polyP), a condensed linear form of orthophosphate residues, is functionally versatile phosphorus (P) polymer that has persisted since prebiotic Earth. Long treated as a cellular biochemical curiosity, it remains systematically overlooked in global P budgets and Earth system models. In this review, we compile the first global-scale synthesis of environmental occurrence, biological regulation, and ecosystem functions of polyP across terrestrial, freshwater, marine, and engineered systems. Integrating 568 environmental observations and over 3000 microbial genomes, we unveil that polyP is a quantitatively significant and phylogenetically widespread component of global P cycling, often comprising 5-40% of total phosphorus in major ecosystems. We synthesize current understanding of how microbial taxa, including bacterial or archaeal polyP-accumulating organisms and arbuscular mycorrhizal fungi, mediate polyP turnover and interact with carbon/nitrogen cocycling under fluctuating redox, nutrient, and climatic conditions. Our quantitative assessment reveals that global polyP stocks in soils, sediments, and wastewater systems form a substantial, yet previously unaccounted, reservoir of recoverable and climate-sensitive P. The omission of polyP from existing models creates systematic blind spots in understanding P bioavailability, retention, cycling, and sustainability. Integrating polyP into the global P narrative is essential for advancing new frontiers in climate-smart biogeochemical forecasts, circular nutrient management, and long-term water-energy-food ecosystem security under global climate change.

Intracellular biopolymers serve versatile functions, allowing microbes to adapt to fluctuating environmental conditions. The metabolic interdependence of dual biopolymers polyphosphate (polyP) and polyhydroxyalkanoates (PHA) is a defining feature of polyphosphate-accumulating organisms (PAOs), the key agents enabling enhanced biological phosphorus removal (EBPR). Beyond EBPR, PAOs accumulating both polyP and PHA (PHA-PAOs) in natural environments remain unexplored due to limited detection tools, despite hypothesized roles in nutrient cycling. This study presents a novel phenotype-targeted approach integrating triple-stained fluorescence-activated cell sorting with 16S rRNA gene sequencing (TriFlow-Seq) to detect, quantify, and phylogenetically characterize PHA-PAOs, validated by fluorescence imaging and single-cell Raman spectroscopy. TriFlow-Seq of EBPR samples confirmed known PAOs, including Candidatus Phosphoribacter, Tetrasphaera, and Ca. Accumulibacter, and revealed new candidate PHA-PAOs within the Rhodobacteraceae family. In maize rhizosphere, TriFlow-Seq led to the discovery of diverse PHA-PAOs, Pseudomonas, Halomonas, and Nannocystis. These genera participate in plant-growth-promoting functions including phosphate solubilization and phytohormone production, yet their simultaneous polyP and PHA accumulation has never been reported. Our findings revealed high PHA-PAO prevalence and distinct phylogenetic patterns associated with different maize genotypes, suggesting an overlooked role of biopolymer costorage in rhizosphere dynamics. This study establishes a pioneering approach to investigating PHA-PAO identities and roles across ecosystems.

Organic pollutants exist in various physical states within the natural environment, yet it remains unclear how their physical states influence their toxicity characteristics. This study investigated the phase-dependent genotoxicity and combined effects of two organic compounds, tert-butyl hydroperoxide (TBHP) and dimethyl sulfate (DES), in both gaseous and aqueous phases. Given the substantial differences in concentrations for the same compound in gaseous and aqueous environments, we constructed the complete multitoxic and dose-response curves for gene induction in both phases, covering environmentally relevant concentrations. Under the same stress conditions, the genotoxicity of gaseous TBHP was 158.21 ± 33.17% of that of its aqueous form, while gaseous DES exhibited 260.56 ± 12.63% of the genotoxicity of its aqueous form. Notably, while no formation of new reaction products were observed, aqueous-phase mixtures exhibited greater complexity and higher toxicity compared to their gaseous counterparts. These differences were attributed to variations in molecular energy states, free radical generation and diffusion, molecular interaction pathways, and chemical reactivity between the two phases. By elucidating the mechanisms underlying these disparities, this study highlights the critical role of physical states in evaluating the toxicity and risks associated with gaseous organic chemicals.

Intracellular biopolymers serve versatile functions that allow microbes to adapt to fluctuating environmental conditions. The metabolic interdependence of dual intracellular polymers, namely polyphosphate (polyP) and polyhydroxyalkanoates (PHA), is a defining feature of functionally polyphosphate-accumulating organisms (PAOs), the key agents enabling enhanced biological phosphorus removal (EBPR) for wastewater treatment. However, beyond EBPR systems, the presence and identities of PAOs that possess both polyP and PHA in natural environments such as soil have never been examined due to a lack of available detection tools, despite their potential roles in carbon and phosphorus cycling. This study presents a novel phenotype-targeted approach integrating triple-stained fluorescence-activated cell sorting (FACS) with 16S rRNA gene amplicon sequencing (termed TriFlow-Seq) to simultaneously detect, quantify, and phylogenetically characterize PAOs accumulating both polyP and PHA (referred to as PHA- PAOs). TriFlow-Seq was validated using polymer staining image analysis and Single-Cell Raman micro-spectroscopy. Application to EBPR systems successfully enriched known PHA- PAOs, including Candidatus Accumulibacter, Tetrasphaera , Dechloromonas , Pseudomonas. It also revealed novel candidate PHA-PAOs, particularly within the Rhodobacteraceae family. When applied to soil samples, TriFlow-Seq led to the first discovery of diverse PHA-PAOs dominated by Pseudomonas , Halomonas , and Nannocystis in maize rhizosphere soils. These predominant genera are known rhizosphere inhabitants of essential crops with key plant growth- promoting functions including phosphate solubilization, biofilm formation, and phytohormone production, yet simultaneous polyP and PHA accumulation has not been directly reported in the maize rhizosphere. Our findings revealed unexpectedly high PHA-PAO prevalence and distinct phylogenetic patterns associated with different maize genotypes, suggesting a potentially overlooked role for dual polymer storage in microbial rhizosphere dynamics and function. This study establishes a pioneering approach to investigate dual polyP and PHA-containing PAO identities and their important roles in rhizosphere structure and plant health. Synopsis: Novel method reveals dual-polymer bacteria in activated sludge and crop rhizospheres, suggesting new candidates supporting wastewater treatment and agricultural sustainability.