Do strictly anaerobic organisms use metabolic reactions requiring oxygen?

Question

When looking through genome annotations of strictly anaerobic organisms I see reactions featuring oxygen. I suspect these are likely an artifact of the annotation process. But I am wondering if it is possible for such organisms to have oxygen associated metabolism. Strict anaerobes are known to die in the presence of oxygen due to the lack oxidative stress pathways. So I cannot think of any reason for oxygen to be part of their metabolism.

Answer 1

Anaerobic organisms can live without oxygen. They could use other elements for their life. They live deep in the ocean or inside the deep cave, in volcano crater.