 So rock and metal are alternatives, and they'll work in a pinch. They're not as efficient or as, you know, great as oxygen, but they can work. So there are microbes that have learned to do this. Some of them will chew rock and metal and bring it into their cells. And others will actually create these like external electrical conduits with the rock or metal that surrounds them. And they can like pass electrons off to their rockier metallic surroundings that way.