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

[Robert Bradbury]

On 4/16/06, Martin Striz <mstriz at gmail.com> wrote:
>
> I said... "Penicillin was produced by Streptococcus."
>
> Where are you getting this information?  It is produced by Penicillium
> moulds.


My very bad.  I was reading the wikipedia entry on penicillin too quickly,
read Staphylococcus (which I have a hard time keeping straight with
Streptococcus) and entirely missed Penicillium chrysigenum (the mould)
entry.

I actually thought I knew it was a fungus that produced penicillin (which is
why I checked it) so I'm going to have to do some brain rewiring to double
check things when I'm doing them too quickly without sufficient coffee in
the morning. :-(

But many of the antibiotic genes are from bacteria -- tetracycline comes
from streptomyces (which is a soil bacteria).  Interestingly, fungi and
streptomyces have rather large genomes so perhaps having a large genome
gives one the extra carrying capacity for weapons to throw at other
microorganisms should the need arise.

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.


Yep.  Though they don't have to be "new" (as in completely novel) -- just
sufficiently different that the penicillin doesn't inhibit the activity.

> > 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.


A nice succinct answer.

R.
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