What if cyanobacteria never evolved

Yet without them we may not be here at all. Cyanobacteria then went a step further: they started to utilise water during photosynthesis, releasing oxygen as a by-product. But we may owe bacteria more than the air we breathe.

It is likely that eukaryotic cells, of which humans are made, evolved from bacteria about two billion years ago. One theory is that eukaryotic cells evolved via a symbiotic relationship between two independent prokaryotic bacteria.

A single bacterium was engulfed by another one, and the smaller cell continued to exist inside the other, which was beneficial to both. They evolved to become the more advanced eukaryotic cell, with its membrane-enclosed nucleus. Regardless of how it happened, the evolution of eukaryotic cells was a significant milestone in the history of life on Earth. As conditions became more favourable, more complex organisms began to evolve.

This shows that D1 and D2 have been evolving separately -- in cyanobacteria and plants they only share 30 percent of their genetic sequence. Even in their original form, D1 and D2 would have been able to perform oxygenic photosynthesis, so knowing how long ago they were identical could reveal when this ability first evolved. To find out the difference in time between D1 and D2 being percent identical, and them being only 30 percent the same in cyanobacteria and plants, the team determined how fast the proteins were changing -- their rate of evolution.

Using powerful statistics methods and known events in the evolution of photosynthesis, they determined that the D1 and D2 proteins in Photosystem II evolved extremely slowly -- even slower than some of the oldest proteins in biology that are believed to be found in the earliest forms of life.

From this, they calculated that the time between the identical D1 and D2 proteins and the 30 percent similar versions in cyanobacteria and plants is at least a billion years, and could be more than that. Dr Cardona said: "Usually, the appearance of oxygenic photosynthesis and cyanobacteria are considered to be the same thing.

So, to find out when oxygen was being produced for the first time researchers have tried to find when cyanobacteria first evolved. This is in agreement with current geological data that suggests that whiffs of oxygen or localized accumulations of oxygen were possible before three billion years ago. There could be a very large gap in time between one and the other.

It is a massive change in perspective. Now, the team are trying to recreate what the photosystem looked like before D1 and D2 evolved in the first place.

Using the known variation in photosystem genetic codes across all species alive today, they are trying to piece together the ancestral photosystem genetic code. Materials provided by Imperial College London. Original written by Hayley Dunning.

Note: Content may be edited for style and length. Science News. William Rutherford, Anthony W. On the origins of oxygenic photosynthesis and aerobic respiration in Cyanobacteria.

The article above mentions the discovery of two lineages of Cyanobacteria. What did scientists figure out about the evolution of photosynthesis in Cyanobacteria based on these two groups? Be sure to describe the evidence that led to these conclusions in your explanation. In your own words, explain the difference between vertical and horizontal gene transmission.

Describe the evidence that supports the idea that photosynthesis arose once and was passed to many lineages via horizontal transfer. How did the evolution of oxygen-producing photosynthesis change the atmosphere? How did this atmospheric shift affect the evolution of respiration? Be sure to include the concept of natural selection in your answer.

Do some research and describe another case in which horizontal transfer played an important role in the evolution of a lineage.

Teach about horizontal transfer : This news brief from for grades explains the quirks of bacterial evolution, including horizontal transfer, that make them such speedy evolvers. Teach about the evolution of photosynthesis and aerobic respiration: These four slide sets targeting undergraduate-level biology address connections between basic metabolic processes and evolution.

Download them using the links below: Photosynthesis 1 Photosynthesis 2 The Krebs cycle Mitochondria and plastids How to use Evo in the News with students. Blankenship, R. The multiple evolutionary histories of dioxygen reductases: implications for the origin and evolution of aerobic respiration. Molecular Biology and Evolution.

Butler, J. May 10, Ley, R. The human gut and groundwater harbor non-photosynthetic bacteria belonging to a new candidate phylum sibling to Cyanobacteria.

Dodd, M. Little, C. Evidence for early life in Earth's oldest hydrothermal vent precipitates. Hohmann-Marriott, M.