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View Full Version : How Did Early Bacteria Survive Poisonous Oxygen?



Fraser
2006-Nov-29, 08:42 PM
Oxygen makes up 21% of the Earth's atmosphere, and we need it to breathe. But early organisms would have found this environment toxic. Ancient bacteria evolved protective enzymes that prevented oxygen from damaging their DNA, but what evolutionary incentive did they have to do this? Researchers have discovered that ultraviolet light hitting the surface of glacial ice can release molecular oxygen. Bacteria colonies living near this ice would have needed to evolve this protective defense. They were then well equipped to handle the growth of atmospheric oxygen produced by other bacteria that would normally be toxic.

Read the full blog entry (http://www.universetoday.com/2006/11/29/how-did-early-bacteria-survive-poisonous-oxygen/)

GOURDHEAD
2006-Nov-29, 09:14 PM
Quoted from the article: The organisms assumed responsible were the cyanobacteria, which are known to have evolved the ability to turn water, carbon dioxide, and sunlight into oxygen and sugar, and are still around today as the blue-green algae and the chloroplasts in all green plants.

But researchers have long been puzzled as to how the cyanobacteria could make all that oxygen without poisoning themselves. To avoid their DNA getting wrecked by a hydroxyl radical that naturally occurs in the production of oxygen, the cyanobacteria would have had to evolve protective enzymes. But how could natural selection have led the cyanobacteria to evolve these enzymes if the need for them didn’t even exist yet? If they waited for the need to arise, they nor we would be here. Evolution in its own mindless fumbling way changes things now and then and sometimes we luck out. It was normal herd maintenance.

Sticks
2006-Nov-29, 10:27 PM
Or maybe there is a flaw with abiogenesis...

GOURDHEAD
2006-Nov-30, 12:01 PM
Or maybe there is a flaw with abiogenesis...
I don't see the connection with abiogenesis. The conditions under discussion are downstream in the river of evolution.