A bacterium has a number of defence mechanisms against different types of stress and regulates them by activating or "turning off" various genes. By studying all a bacterium's genes and the biomolecular changes in a bacterium, the bacteria's secret weapons can be revealed.
One method of studying the bacteria's defence mechanisms is to add, for example, hydrochloric acid to a bacterial culture in the middle of a growth phase. The bacteria receive a shock and mechanisms within them start working overtime to neutralise or pump out the acid and to repair damaged molecules in the cell. By studying all the genes in the bacterium before and after the acid shock, we can learn something about which mechanisms bacteria use to defend themselves against disinfection agents.
