Poisonous substances produced by some microorganisms are called

Poisonous substances produced by some microorganisms are called microbial toxins.
Microbial toxins are produced by bacteria and fungi and those toxins promote infection by directly damaging host tissues. Also, toxins may cause a disease by disabling the immune system.  Microbial toxins can have important uses in medical science and research, but their effect also may be dangerous (for example, neurotoxin such as Botulinum).