On Thu, 8 May 2003 21:56:07 +0000 (UTC),
s_sankar_balaji{at}rediffmail.com (Sankar) wrote:

>Hi,
>
>  I am having this doubt.
>
>  Bacteria are organisms which grow and reproduce much faster. So they
>evolve very soon too. But over the centuries, why didn't bacteria
>evolve to decompose plastics and other synthetics?
>
>  If bacteria is evolving to adapt to the environment, in an world of
>increasing usage of plastics and synthetic materials, why is bacteria
>not adapting to it?
>
>  Or is it that, bacteria are trying to decompose plastics but leaving
>back a hazardous partially decomposed material, which results in land
>pollution?
>
>Thanks,
>sankar

Plastics that are easily decomposed by bacteria tend not to be too 
useful -- they don't last very long!  So people tend to spend a lot of
time thinking up things that bacteria can't get at. Developing useful
biodegradable products is very difficult -- you either get a product
that decomposes while you are using it or one that lasts far too long.

Also, dry, hard, solid materials tend to be very poor substrates for
bacterial decomposition.  So cloth (made from natural fibers) and
leather, and such tends to last for a fairly long time and is only
slowly degraded.

Finally, many types of organisms, plant and animal alike, have managed
to cover their outsides with special proteins or carbohydrate polymers
that are very poorly degraded as protection against bacterial
invaders.  So we have cellulose (cotton and linen) and keratin (wool)
and insect pupal cases (silk) that are relatively long lasting.
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