Tuesday, 14 February 2012

More Evidence To suggest That Life First Arose In Areas Of Extreme Volcanic Activity

The Grand Prismatic Spring in Yellowstone National Park is perhaps the
closest we can get to a fresh water version of the primordial soup.
Yellowstone is of course a region high in geothermal activity. 
The origins of life have been a hotly debated subject for many years. In the mid 1800s, Louis Pasteur created the theory of biogenesis which states that all life must come from a previously living organism. In doing this, however, he created a scientific void: where did the first organisms come from? His ideas were widely accepted because this void seemed to fit in with the religious views of the time: the view that god created all organisms.
In the 1830s to 1850s when Charles Darwin provided evidence that organisms evolved, the debate over the origins of life started up once again. During the early to mid 1900s, biochemical experiments defined the conditions in which life could arise from inert chemicals. These conditions have helped narrow down where life could have begun. Many theories state that early organisms formed and lived around deep sea hydrothermal vents due to the heat, protection from solar radiation and a rich variety of chemical compounds.

Yet scientists are beginning to move away from the deep sea theory and look towards shallow pools and lakes around volcanoes and other such areas of intense geothermal activity. Over the past five years, biochemical experiments have backed this up, giving reasons why proto-cells would require a shallow, volatile environment powered by volcanoes. Now a new experiment has provided evidence to show that the cellular composition of organisms today could only have evolved as a result of life's origins in shallow volcanic pools.

The cytoplasm of cells are rich in element ions. Living organisms use the different charges to generate a form of bio-electricity which power their various life processes. It is likely that the membranes of early creatures were very simple and unable to control the flow of substances in and out of the cell, as structures such as protein gates had not yet evolved. As a result, the ionic composition of the cytoplasm would have been very similar to the water in the surrounding environment.

The bizarre structures within the membrane, such as the Golgi complex
or the ribosomes are all biological engines composed of proteins which
carry out the processes which fuel the cell.  Many of these engines cannot
function in sodium rich environments as shown by Mulkidjanian's research 
A team of scientists, led by Armen Mulkidjanian from the University of Osnabrück in Germany, conducted a genomic and geological investigation into the environment in which the first cells lived. Seawater contains a high level of potassium, zinc and phosphate ions and low concentrations of sodium. Fresh and condensed water, the kinds found in volcanic pools, has the opposite concentrations of ions.

Firstly, the team had to find evidence to show that the ionic composition of the cytoplasm has not changed over time. They did this by examining protein structures within cells and charted when they evolved using genetic analysis of simple forms of bacteria and archaea. They found that these essential pieces of cellular machinery were present either in the first ever life form (properly called LUCA, the last universal common ancestor) or its very close descendants.

The proteins can only form and function in environments which are low in sodium ions but rich in phosphate, potassium and zinc. A source of heat would also be required alongside an abundance of minerals and chemical compounds. The environments which tick all of these boxes are the shallow, freshwater pools found in areas of intense geothermal activity. While past studies have shown, through complex chemistry, why such places are ideal for the formation of life, this one has provided direct evidence in its role in the biological link between modern day organisms and their many billion year old ancestors.