Ammonium and methane are known to be relatively difficult to activate with reactions catalyzed by enzymes that make use of high-potential oxygen radicals, which are unavailable to anaerobic life, leading to the assumption that both compounds were effectively inactive in low oxygen environments [REF].
During the past, many microorganisms such as anammox bacteria may have escaped discovery due to their relatively low growth rates requiring very efficient biomass retention absent from classical methods of cultivation [REF].