Ancient Bacteria Were Breathing Long Before Oxygen Became Abundant

Today, oxygen makes up about 21% of our atmosphere, but it wasn’t always so plentiful. Around 2.7 billion years ago, cyanobacteria—aquatic bacteria that generate energy through photosynthesis—evolved and began releasing oxygen into the oceans. This oxygen gradually accumulated in the atmosphere in a process called the Great Oxidation Event (GOE), which took place between 2.4 and 2.1 billion years ago. New research, however, suggests that aerobic (oxygen-dependent) bacteria may have emerged long before the GOE. An international team of researchers has reconstructed the evolutionary tree of one of Earth’s earliest life forms, revealing that bacteria may have adapted to the presence of oxygen long before it was plentiful in our atmosphere. Their work, detailed in a study published today in the journal Science, challenges the previous assumption that most life prior to the GOE was anaerobic, that is, organisms that don’t need oxygen to survive. The researchers used a multidisciplinary ap ... Read full article.