When a malaria-carrying mosquito bites a human host, the malaria parasite enters the bloodstream, multiplies in the liver cells, and is then released back into the bloodstream, where it infects and destroys red blood cells.
A mosquito becomes infected with malaria when it sucks the blood from an infected human. Once inside the mosquito, the parasites reproduce in the gut and accumulate in the salivary glands, ready to infect another human host with the next bite.
Bacteria can transfer genetic material, and thus drug resistance, to other bacteria via conjugation.
Watch this animation to see the molecular tricks that an infectious strain of Escherichia coli uses to infect your gut.
In this animation, you can see how one S. typhimurium invades an epithelial cell of the intestinal tract, survives the intracellular defense mechanisms of the host cell, and multiplies.