Rapid changes in gene expression levels are necessary for the survival of bacteria, notably in highly competitive environments. By being able to quickly up- or down-regulate gene expression, stress response genes (to respond to stimuli like pH change, temperature, nutrient absence, etc…) can quickly be expressed to allow the organism to survive.
For example, acid-stress response genes need to be rapidly upregulated during campylobacter infection of the gastrointestinal (GI) system. This pathogen is typically found on raw poultry, from poor agricultural and butchery practices, and is a dominant cause of food poisoning. Due to the route of infection being through the GI system, the bacteria must be able to survive rapid pH changes on entering the stomach, and subsequently the ileum. As campylobacter is able to respond quickly to this environmental change, it is able to successfully infect the victim’s intestine, colonising and inducing diarrhoea.
Another pathogen found in a highly competitive environment is methicillin-resistant Staphylococcus aureus (MRSA). This pathogen it frequently found commensaly on patient’s skin, alongside many other bacteria. However, if the skin is punctured or other bacteria are killed, MRSA rapidly colonises, before expressing virulence factors. [this does not require rapid gene regulation, so probably isn’t relevant].
Heat-shock, where a rapid temperature change is experienced, also requires rapid gene expression changes. Using the sigma-32 sigma factor, heat-shock genes are quickly upregulated. As sigma-32 is constitutively expressed in the cytoplasm of bacteria, consisting roughly 1/3 of the sigma factors present (with sigma-70 being dominant during good growth conditions), it is quick to change the regulons being expressed. During heat-shock, chaperone proteins are necessary to stabilise cytoplasmic protein, as well as proteins recognising denatured forms and catalysing degradation pathways. It is important denatured proteins are degraded rapidly, as coagulation of protein in the cytoplasm will lead to cell death. Stabilising existing proteins allows the bacterium to continue to function. Combining the different methods of survival will hopefully allow the bacteria to survive, enabling it to colonise the areas left by other colonies that did not survive the stress.
As heat-shock is a rapid stress, it is necessary for the bacteria to be able to respond quickly, ensuring their survival. A competitive environment experiencing heat-shock could include electrical equipment.