Cells, complexity and the meaning of life and death

25 October 2010

 Three mitochondria surrounded by cytoplasm. Wellcome Images
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Three mitochondria surrounded by cytoplasm. Wellcome Images

When Nick Lane told a Packed Lunch audience that his latest theory on the birth of complex life had been nine months in the making, it seemed a fitting gestation period. Unfortunately he had just half an hour to tell us about it.

Nick is a writer and biochemist at UCL, where he holds the first Provost’s Venture Research Fellowship in the Department of Genetics, Evolution and Environment, and is a founding member of the UCL Consortium for Mitochondrial Research. His research on the role of bioenergetics in the origin and evolution of complex life is fascinating.

Bioenergetics is the study of the energy flow through the body. Our energy comes from the molecules in the food we ingest. This energy is converted as part of respiration by mitochondria, the cellular ‘power plants’, into a molecule called ATP that can transport chemical energy within cells, enabling the chemical reactions that support life.

Nick wants to know exactly how and why mitochondria came to be in complex cells. The first forms of life were prokaryotes – small, simple cells. Eukaryotes, larger cells with mitochondria and other organelles, came after prokaryotes on the evolutionary timeline. It is supposed that eukaryotes evolved from prokaryotes. How, and why? It is generally believed that at some point in history, a large prokaryotic cell, such as a phagocyte, engulfed an ancestral form of a mitochondrion that once existed as a free-living organism. There is much argument and acrimony over how, when and why this happened.

After gaining a PhD in biochemistry, Nick spent ten years ruminating on these questions as a professional writer, during which time he “rove across the world – a wonderful freedom”. He has authored three books: ‘Oxygen: The molecule that made the world‘; ‘Power, Sex, Suicide: Mitochondria and the meaning of life‘; and ‘Life Ascending: The ten great inventions of evolution‘ (which has just been awarded the Royal Society Prize for Science Books 2010). But through his exploration of these topics, he found that “time and time” again his own understanding “fell flat on its face”. It was time to go back to the lab.

Nine months ago Nick started scribbling on the back of an envelope. He was sketching out an idea that related extra energy to extra genes. At the moment of endosymbiosis, when an ancestral mitochondrion partnered with a eukaryotic cell, the genes from the mitochondrion provided the large cell with the “raw material for evolution”. Nick now supposes that the extra energy provided by the mitochondrion enabled the cell to support these extra genes. Whereas prokaryotic cells do not have the energy to carry large amounts of DNA, eukaryotic cells, with their mitochondrial powerhouses, can. This theory will be published in ‘Nature’ after five months of review. Nick says “some people will hate this paper”. Argument and acrimony.

Nick is also interested in the role mitochondria play in disease, and particular disorders related to ageing. Free radicals are an essential byproduct of the respiration process that happens in mitochondria. They ‘leak’ from mitochondria, which can cause damage in the body. Other scientists are researching free radicals as the causes of cancer, Parkinson’s disease, schizophrenia and Alzheimer’s. Nick is looking into how antioxidants and calorie restriction diets might be able to ‘mop-up’ free radicals and reduce the number that leak from mitochondria, thus reducing the damage they do. This work is ongoing. For the moment, it seems that mitochondria hold some of the secrets of both life and death.