Scha - bacterial toxins

[Guest guest]

The endotoxin (lipopolysaccharide) of gram-negative bacteria and some

spirochetes (but not Tp or Bb) are not really toxins in the same

sense as staph toxins. LPS is hydrophilic and is found on the

exterior of the outer membrane where it prevents the indiscriminate

passage of lipophilic molecules thru the outer membrane into the

periplasmic space. It does not interefere with vertebrate metabolism

as far as I know, but does cause morbidity and mortality via ligation

of the omnipresent innate immune receptor TLR-4.

Staph toxins are intetionally released by staph into the host to

create an effect, the classic one being hemolysis. I'm not sure but I

think this is an effort to liberate nutrients? Also, staph toxins

(the same? different?) are able to kill phagocytes which have

ingested the staph. M. tuberculosis also has a cytolytic toxin which

it uses to free itself from macrophages. Absence of the gene for this

toxin is probably what makes the BCG tuberculosis vaccine strain

attenuated (tho I believe some feel it is not attenuated enough and

is dangerous).

Staph hemolytic toxins can be observed in culture. You just put blood

on the culture plate and look for it to be cleared in a zone around

the staph colonies.