Impacts of rare earth metals and symbiosis on bacterial methane consumption

The greenhouse gas methane (CH₄) has a much higher global warming potential per molecule than carbon dioxide (CO₂). Since methane levels have been rising in the past decade, an understanding of contributors to the methane cycle is necessary to predict and mitigate climate change. The success of bacteria that consume methane (methanotrophs) determines which habitats emit methane. Research from this decade has revealed that many bacteria, including methanotrophs, contain central metabolic enzymes that rely on rare earth metals, or lanthanides (Ln³⁺). Bacteria that utilize lanthanides must have some mechanism for uptake or interaction, so they are also excellent candidates for bio-recycling these metals commonly used in batteries, hard drives and magnets.

It is becoming clear that rare earth metals are not the only factor regulating the central methanol dehydrogenase reaction. Methane-utilizers and methanol-utilizers exist in communities in habitats ranging from lakes to oceans to grasslands, characterized by cross-feeding of methanol (CH₃OH) and possibly other molecules. When grown together, a methanotroph/non-methanotroph pair from Lake Washington can alter one another’s gene expression, including the transcriptional response to lanthanides. The mechanisms of this phenomenon are currently under study, including the effect of nitrogen oxide metabolism on the regulation of methanotrophy. Unraveling these interactions relies on traditional genetics, gene expression analysis, flow cytometry, mass spectrometry metal measurements, and synthetic community studies.