Resource availability governs polyhydroxyalkanoate (PHA) accumulation and diversity of methanotrophic enrichments...

Aquatic environments account for half of global CH₄ emissions, with freshwater wetlands being the most significant contributors. These CH₄ fluxes can be partially offset by aerobic CH₄ oxidation driven by methanotrophs. Additionally, some methanotrophs can convert CH₄ into polyhydroxyalkanoate (PHA), an energy storage molecule as well as a promising bioplastic polymer. In this study, we investigate how PHA-accumulating methanotrophic communities enriched from wetlands were shaped by varying resource availability (i.e., C and N concentrations) at a fixed C/N ratio. Cell yields, PHA accumulation, and community composition were evaluated in high (20% CH₄ and 10 mM NH₄ ⁺) and low resource (0.2% CH₄ and 0.1 mM NH₄ ⁺) conditions simulating engineered and environmental settings, respectively. High resource availability decreased C-based cell yields, while N-based cell yields remained stable, suggesting nutrient exchange patterns differed between methanotrophic communities at different resource concentrations. PHA accumulation was only observed in high resource enrichments, producing approximately 12.6% ± 2.4% (m/m) PHA, while PHA in low resource enrichments remained below detection. High resource enrichments were dominated by Methylocystis methanotrophs, while low resource enrichments remained significantly more diverse and contained only a minor population of methanotrophs. This study demonstrates that resource concentration shapes PHA-accumulating methanotrophic communities. Together, this provides useful information to leverage such communities in engineering settings as well as to begin understanding their role in the environment.