Of course, no-one can predict the future, but if does seem likely that microbes will outlive humans, and probably many other kinds of living things too.

The comparison is in many ways a bit unfair, because humans are just a single species (albeit a rather numerous one), and species tend to have a fairly high ‘turnover’ – (I couldn’t find a reference for how quick this is, but you could try looking in the books edited by Groombridge and Benton in the list below).

Anyway, certain things about bacteria make it likely they’ll be around for quite a long time to come. For a start, they have certainly already been here for a long time – the earliest fossils of bacteria are at least 3500 million years old, and there are fairly complex microbial communities in the 2000 million-year-old Gunflint Iron Formation of Canada (see Knoll, 199?).

Bacteria and other microbes are also rather seriously numerous – there are millions of them in every gram of soil, and there are probably millions of different types of bacteria. In fact, no-one is sure how many types of bacteria there are. Because microbiologists traditionally only study bacteria they are able to grow in the laboratory, only a few thousand bacterial ‘species’ are known in any detail, but several studies suggest that millions of others exist – see Truper (1992).

Bacteria are also able to live in almost any conditions – there are examples that live in extremely hot and extremely cold environments, in very salty places and at incredibly high pressures in the deep ocean. It’s likely that however the earth’s environment changes in the future, at least some bacteria will be able to live there still. There is even one impressive bacterium (Deinococcus radiodurans) able to withstand massive doses of radiation.

It seems almost certain that bacteria will outlive people, not least because every person probably has at least as many bacteria inside them as they have human cells!

I hope this is of some help,

Yours,
James

FOR GENERAL MICROBIOLOGY STUFF, TRY LOOKING IN :- BROCK, T. D. AND MADIGAN, M. T. (1991). BIOLOGY OF MICROORGANISMS, 6^th ed. Prentice Hall, London.

BENTON, M. J. (1992). THE FOSSIL RECORD 2.

GROOMBRIDGE, B. (1992). Global biodiversity : status of the Earth's living resources. Chapman & Hall, London.

KNOLL, A. H. (1990) Precambrian evolution of prokaryotes and protists. In Palaeobiology: a syntheses (D. E. G. BRIGGS AND P. CROWTHER, eds.). Blackwell Scientific, Oxford.

TORSVIK, V., GOSKØYR, J., AND DAAE, F.L. (1990). High diversity in DNA of soil bacteria. Appl. Env. Microbiol. 41:518- 527.

TRUPER, H.G. (1992) Prokaryotes: An overview with respect to biodiversity and environmental importance. Biodiversity and Conservation 1:227-236.

WARD, D.M., WELLER, R., AND BATESON, M.M. (1990). 16S rRNA sequences reveal numerous uncultured microorganisms in a natural community. Nature 345:63-65.