Scientists have identified a key difference in the way our immune systems respond to viral and bacterial pathogens. ... These hormone-like molecules control communication between cells to trigger defensive action by the body's immune system when pathogens such as bacteria, viruses, or parasites are detected.
It is produced industrially by fermentation using yeast or bacteria. Marmite's defining ingredient is made from brewer's yeast heated to create glutamic acid, which is used by farmers to increase plant growth and boost crop yields.