A lone microbe proves methane producing archaea do not always need partners

A solo act underground

Textbooks have long taught that breaking oily fats into natural gas takes a strict microbial tag-team. Bacteria were thought to chop up heavy fats first, leaving simple scraps for specialised methane producing archaea to finish off.

A newly isolated strain named Methanoglobus dolicholipophagus AA-75 just broke that rule. Grown in a pure lab culture from an oil reservoir, this single heat-loving archaeon digests complex fatty acids entirely on its own.

Running the whole kitchen

Think of this microbe like a solo chef who preps, cooks, and plates a complicated meal from scratch, rather than relying on an outside prep cook to chop the raw ingredients. The cell handles the entire chemical chain indoors.

Inside the cell, a process called beta-oxidation snips fatty acid chains ranging from C7 to C18 into smaller fragments. It feeds these directly into the Wood-Ljungdahl pathway to generate methane, carbon dioxide, and acetate. It also has no trouble turning methanol into fuel. Because all electrons stay inside the cell, it never needs an external partner to mop up excess waste.

This distinct lifestyle, called lipotrophic methanogenesis, leaves a telltale mark. The resulting gas has an unusually heavy carbon isotope signature, measuring between -40.0‰ and -36.3‰ for stearate, looking noticeably different from typical biological methane.

What we still don't know

This does not mean partnered decay never happens. Rather, it reveals that methanogens are not strictly trapped at the very end of the food chain, waiting on simple leftovers.

However, this direct breakdown has only been confirmed in strain AA-75 under controlled laboratory conditions. Biologists still do not know how much this solo pathway contributes to real-world underground carbon cycles compared to classic microbial partnerships. The exact inner mechanics of its supporting formaldehyde-methanol branch also remain to be verified.