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Life on the Edge ... and beyond!

Some related articles I have written after preparing the paperback version (Sept. 2000), newest first:

• Gross M: Chemistry in Britain 37, No 8, 21
  Sticking to stones
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Update to the hardback version (end 1997-summer 2000)

The first edition of Life on the Edge was went to the printers at the end of 1997, but research keeps moving on. Here I have collected a list of important findings that have happened since then, most of which I have also included in additional notes and the afterword included in the paperback edition of the book.

• Snowball Earth: Throughout the book, I keep saying how nicely the climate on our planet has remained within habitable limits over the past three billion years. Well it turns out that maybe it hasn't. According to a radical new theory published by Harvard geologist Paul Hoffman and others in August 1998, the oceans may have been completely covered with ice for millions of years, just before the precambrian explosion, some 600 to 800 million years ago. The theory has been hotly debated ever since. It has the merit of explaining seamlessly some weird geological observations, including traces of glaciers in places which must have been near the equator at the time. If the most extreme version of the theory were true, life on Earth must have been very close to complete extinction at that time. Some more moderate versions, including a simulation published in Nature in May 2000, suggest that some open ocean water may have been around even in the worst glaciation times, providing niches for a diverse biosphere to survive.
• Methane hydrate: Deposits of this strange "burning ice" at the sea floor were found to be much larger than anticipated, and inhabited by bristle worms (polychaetes) and archaebacteria that can feed on the methane. Thus they form a major extreme biotope, as well as a potential threat to our climate. If a significant part of the methane trapped in this state were set free, this could trigger a runaway greenhouse warming.
• Tardigrades, a group of microscopically small animals living in the moisture droplets in moss, have been shown to survive hydrostatic pressures of up to 6000 bars. Part of their survival secret involves the generous production of the sugar trehalose which is also used by yeast and other organisms for heat protection.
• Lake Vostok: New measurements have shown that as the iceshield moves across the lake, some ice melts and mixes with the lake at the leading edge of the lake (the shore which meets the new ice first) while lake water refreezes at the opposite side. The drilling project has found traces of bacterial life in a layer of ice known to consist of such re-frozen lake water . Robotic instruments that can dig themselves through the ice without leaving an open hole that would permit contamination are being developed both for Lake Vostok and for future missions to Europa.
• Molecular chaperones: Crystal structures of GroEL in various shapes and sizes have been piling up in recent years. A serendipitous outcome of a crystallographic study of the substrate binding domain has resulted in a preliminary characterization of the molecular interaction with substrates, as a part of the protein construct was unexpectedly regarded as a substrate molecule by neighbouring molecules in the crystal. In early 2000, a crystal structure of the complete 14mer with a bound peptide was reported. Biochemical studies of the chaperon pathway have also progressed, and a detailed register of the proteins that require assistance from GroEL in E.coli was reported in December 1999.
• Genes for high pressure adaptation: Genetic studies on the barophilic Photobacterium profundum SS9 and of a pressure sensitive mutant have led to the identification of genes required for the pressure resistance of this organism.
• Heat shock protein HSP90 is found to play a double role in Drosophila. In the absence of stress it silences mutations. It thereby allows the fly population to build up a certain amount of genetic variability which remains unseen until a stress condition arises. This mechanism represents an unprecedented link between environmental stress and the frequency of phenotype alterations, which could explain the observation that evolution can alternate between apparent stagnation and sudden leaps.
• Thermotoga maritima: The complete genome sequence published in 1999 shows massive horizontal gene transfer even between the domains of eubacteria and archaea.
• ... erm, and then there was NASA's Mars program, which you may have heard of ...