A contemporary meal on Jurassic coal
Deep beneath the Surxondaryo Region of southern Uzbekistan, vast seams of Jurassic coal are slowly being consumed. The coal itself, formed from plant matter that died during the age of dinosaurs, is not the focus. Instead, the focus is on what is eating it: a community of microbes that are actively producing enormous quantities of natural gas. This is coal bed methane, but with a twist. Standard geological processes, involving heat and pressure over millions of years, typically create "thermogenic" methane. The gas in the Surxondaryo Basin is different; it is "biogenic," a waste product of microorganisms metabolizing ancient carbon in the permanent darkness of the subsurface.
The proof of this modern-day gas factory comes from isotopic analysis. Methane is a simple molecule (CH₄), but the carbon and hydrogen atoms within it can have different numbers of neutrons, creating isotopes. Methane produced by heat and pressure has a distinct isotopic signature compared to methane produced by life. Scientists analyze the ratio of carbon-13 to carbon-12 (expressed as δ¹³C). The δ¹³C values for the Surxondaryo methane are significantly "lighter"—more negative—than those of typical thermogenic gas, pointing squarely to a biological origin. This indicates that the gas is not from the Jurassic period but is being generated continuously in the present.
The methanogen workforce
The organisms responsible for this process are methanogenic archaea, a group of single-celled lifeforms that thrive in oxygen-free environments. They are the final step in a complex food web. First, other bacteria break down the complex, long-chain hydrocarbon molecules of the coal into simpler compounds like acetate, hydrogen, and carbon dioxide. The methanogens then consume these simpler substances and release methane as metabolic waste. Two of the primary chemical reactions are CO₂ reduction (using hydrogen to reduce carbon dioxide) and acetoclastic methanogenesis (splitting acetate into methane and CO₂).
These microbial communities are not unique to Uzbekistan; they are found in coal seams globally, from the Powder River Basin in the United States to the Surat Basin in Australia. Each basin hosts a distinct community of microbes adapted to the specific local geology and water chemistry. The Surxondaryo field is part of a large geological structure known as an artesian basin, where water pressure and hydrogeology affect how the gas is formed, trapped, and potentially extracted. The presence of water is essential, as it transports nutrients and the microbes themselves into the coal seams. This process is a renewable form of natural gas, where ancient, buried carbon is recycled by living organisms into a usable fuel.