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Sugar, spice and everything nice... The search for elemental ingredients of life

Aditya Chopra, Charles H. Lineweaver, Jochen J. Brocks and Trevor R. Ireland

Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia

We are finding out if the most primitive organisms on Earth started out with basic ingredients of life and became more complex as they evolved. The findings from the research, could give hints on where and how life got started on Earth.

Over the next few years, we will collect samples of bacteria and archaea (a very ancient form of bacteria). The samples will include including extremophiles, the life forms that thrive in punishingly hot or acidic environments. We then use atomic emission spectrometry, mass spectrometry and elemental analysers to know precisely what these life forms are made of. We will measure the abundances of about half of the 80 most abundant stable elements in nature including major elements such as carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus and trace elements such as sodium, potassium, calcium, iron and copper.

With this information we will find out if the most ancient life forms are made of fewer elements than the life forms that appeared on Earth more recently. Just as a novice chef starts baking a cake with simple ingredients like flour, eggs and sugar, life may have started with the most abundant (or bio-available) elements. These could be elements like carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus and ions like calcium or boron to stabilise its structures, and catalytic metals like iron.

Later, life began to accessorise with more elements like bromine and selenium – like an experienced chef who has learnt to use vanilla, cinnamon and the rest of the spice rack. This increase may be in response to changes in the bioavailability of elements in environments such as the oceans – particularly during the great oxidation event ~2.4 billion years ago.

Aditya Chopra, Charles H. Lineweaver, Jochen J. Brocks and Trevor R. Ireland, Palaeoecophylostoichiometrics: Searching for the Elemental Composition of the Last Universal Common Ancestor, in Australian Space Science Conference Series: 9th Conference Proceedings (submitted)

Figure 2. A possible sequence of increasing diversity of elements used by life.