During the Permian–Triassic extinction event (250 million years ago) a severe anoxic event seems to have occurred where these forms of bacteria became the dominant force in oceanic ecosystems, producing copious amounts of hydrogen sulfide.
Durante o evento de extinción do Permiano–Triásico (hai uns 250 millóns de anos parece que ocorreu un grave evento anóxico no que estas formas de bacterias se fixeron dominantes nos ecosistemas oceánicos, producindo copiosas cantidades de sulfuro de hidróxeno.