Some bacteria are happy at over 100 degrees Celsius (in water under pressure); others can survive freezing and remain active almost as long as water remains liquid. Bacteria can live under intense pressure on the ocean floor, in saturated salt solutions, in acidic and alkaline environments (from pH 2 to pH 13) and, of course, in anaerobic environments. Some bacteria can tolerate these environments; others actually require them.
When it comes to diet, there are bacteria which metabolise iron, sulphur, hydrogen, acids, oils, and even stranger things. Bacteria capable of fixing nitrogen are a particular oddity, as well as of critical importance in global ecosystems. Another surprise are bacteria which can live on very dilute concentrations of nutrients, obtained from the air or from distilled water; these have caused all sorts of headaches for experimental microbiologists.
Postgate also looks at other aspects of bacterial life. Bacteria can move about and exhibit a wide range of sensory abilities, including vision and sensitivity to the Earth's magnetic field as well as the obvious range of chemical senses. The production of antibiotics by some strains of bacteria is one of the strangest (if useful!) phenomena — Postgate ties this in with their evolutionary history. Bacteria are participants in a wide range of symbiotic relationships, both with others of their own kind and with higher organisms. Bacteria which divide into two without a distinguished parent have a possible claim to immortality; bacterial spores can certainly survive for centuries and possibly for millennia. Postgate concludes by considering what the flexibility of bacteria tells us about the possibility of life on other planets and moralising a little about the human population explosion (with the behaviour of overcrowded microbes pointing the lesson); he finishes on a more hopeful note by suggesting a role for bacteria in the terraforming of Mars.
The Outer Reaches of Life is a genuinely popular work of science. It contains no equations or chemical formulae and could, I think, be read happily by a smart primary school child. On the other hand, while the massively simplified explanations of pH and DNA replication were hardly new to me, they were easily skipped; I wasn't expecting to learn any general biology from The Outer Reaches of Life, but I did learn a lot of new things about microbes. Postgate has produced a really enjoyable little book, suitable for anyone interested in general science who isn't already familiar with the material. The next time I'm looking for some light scientific reading I will have a look at his earlier book, Microbes and Man.