The part about &quot;The bacteria&#x27;s ability to oxidise methane and carbon dioxide is of particular interest.&quot; -- which seems to mean &quot;ability to oxidise carbon dioxide&quot; -- can&#x27;t be right. Maybe the meaning is methane to CO2?<p>How can you still extract energy from a O=C=O molecule without using something like flourine? On the other hand, how does the CO2 get back into the carbon cycle? Do the organisms use an endothermic process to get the carbon back?<p>And has the 10% oxygen content been there since the cave was opened? Or was this the first mass extinction? While the water does not reach the cave, is there a way for air to make it through? I would expect no oxygen otherwise.