This document compares the characteristics of exotoxins and endotoxins. Exotoxins are extracellular proteins produced by both Gram-positive and Gram-negative bacteria, while endotoxins are integral parts of the cell wall of Gram-negative bacteria only. Exotoxins are relatively unstable and highly toxic, can be converted to toxoid through heating, and bind to specific receptors on cells. In contrast, endotoxins are more stable, moderately toxic, cannot be converted to toxoid, and do not bind specific receptors.

1. ExotoxinvsEndotoxin
Characterisitics Exotoxin Endotoxin
1.Def
n
Extracellularcomponentof
thecellandexcretedbythe
cell.
IntegralpartofcellwallofGram
-vebactetria.
2.Bacteria ProducedbybothGram+ve
angGram-vebacteria.
FoundonlyinGram-vebacteria.
3.Nature ProteinwithMW10,000-
900,000
Polysaccharidecomplexes;lipid
Aportionprobablyresponsible
fortoxicity.
4.Stability Relativelyunstable;toxicity
oftendestroyedbyheating
attemperatureabove60
o
C.
Relativelystable;toxicity
withstandheatingat
temperatureabove60
o
Cforan
hour.
5.Toxicity Highlytoxic.
Fataltoanimalinmg.
Moderatelytoxic.
Fataltoanimalin10-100mg.
6.Toxoid Convertedtotoxoid. Notcovertedtotoxoid.
7.Immuogenic Highlyimmunogenic Weaklyimmunogenic.
8.Specific
receptors
Usuallybindtospecific
receptorsonthecell.
Specificreceptorsnotfoundin
thecell(notaprotein).
9.Controlling
gene
Frequentlycontrolledby
extrachromosomalgenes
(e.g.Plasmid,Phage)
Synthesisdirectedby
chromosomalgenes.
10.Fever Usuallydonotproducefever
inthehost.
Usuallyproducefeverinthe
host.