Microbes that manipulate the behaviour of their host (like Toxoplasma gondii or Cordyceps) are not limited to nature´s dark corners, although those examples are vivid. Our body hosts vast number of foreign microorganisms, some of which wield unseen power over us. These microbes are not parasites – they live on and in our body, mostly in our gut and often strike up a symbiotic relationship with us.
Composed mostly of bacteria, but also viruses and fungi, this so-called microbiota churns out a complex cocktail of biologically active compounds. Some of these products (substances) closely resemble human hormones and neurotransmitters, the chemicals that neurons use to communicate with one other. Microbes in the gut have long being known to play a role in human health. Irritable bowel syndrome and stomach ulcers, for example, are linked to an imbalance of microbial population.