[extropy-chat] magic johnson, aids, longevity ...

[Martin Striz]

On 4/15/06, Robert Bradbury <robert.bradbury at gmail.com> wrote:

> It is easier to acquire resistance by horizontal gene transfer than it is to
> create de novo mutations.  Many of the original antibiotic resistance genes
> (or a minor variant) probably in bacteria or fungi that needed those
> defenses long before humans started discovering and using antibiotics.
> Generally speaking one has to have many larger numbers of organisms to get
> the right set of mutations when more mutations are required.  Antibiotic
> overuse contributes to the possibility that a bacterial strain will evolve
> and be selected for that has organized one a single small piece of DNA with
> a multi-gene antibiotic resistance set.  The reason to limit antibiotic
> misuse or overuse is to attempt to lower the probability of such
> developments.

There's a remarkable symbiotic relationship that was discovered among
a species of ant that grows bacteria which produce antibiotics against
parasites that infect the ant's food.  As parasites evolve resistance,
the bacteria evolve new antibiotics.

http://cas.bellarmine.edu/tietjen/Ecology/fungus.htm

The lesson: fight evolution with evolution.

> Bacteria for the most part have relatively similar machinery and most of
> them have DNA repair mechanisms that make it difficult to create lots of new
> mutations on short notice -- millions or billions of years of evolution
> between competing organisms in the soil, lakes or water has a much greater
> chance of producing weapons and counter-weapons.  Penicillin was produced by
> Streptococcus.

Where are you getting this information?  It is produced by Penicillium moulds.

> Presumably the penicillin resistance genes came from a
> different bacterial strain competing for resources with Streptococcus.

Penicillin binds and inhibits the transpeptidase enzyme in bacteria,
which prevents the formation of peptidoglycan cross-links in the cell
wall, so the cell ruptures.  The bacteria that develop resistance are
those that evolve new transpeptidase enzymes.

> > If antibiotic cocktails are not a good idea, why is this, exactly?

Because creating stronger selection pressures increases the rate of
evolution, in this case, of resistant strains.

Martin