A new study by researchers at Imperial College London has identified a way in which Salmonella bacteria, which cause gastroenteritis and typhoid fever, counteract the defence mechanisms of human cells.
One way in which our cells fight off infections is by engulfing the smaller bacterial cells and then attacking them with toxic enzymes contained in small packets called lysosomes.
Published today (Thursday) in Science, the study has shown that Salmonella protects itself from this attack by depleting the supply of toxic enzymes.
Lysosomes constantly need to be replenished with fresh enzymes that are generated from a factory within our cells. These enzymes are carried from the factory along a dedicated transport pathway. After dropping off new enzymes at lysosomes, the transport carriers are sent back to the factory to pick up new enzymes.
In the study, led by Professor David Holden from the Department of Medicine and MRC Centre for Molecular Bacteriology and Infection, the group discovered that Salmonella has developed a specific way to interfere with the system that restocks the lysosomes with enzymes. They found that after bacteria have been engulfed by the cell, but before they are killed, Salmonella injects a protein that prevents the cell from recycling the transport carriers between the factory and the lysosome.