Bacteria have many industrial uses including the production of cheese and yoghurt, paper making, biogas and the synthetic production of hormones like insulin. Viral infections of these bacterial cultures can halt production processes resulting in significant financial cost. When the bacteria were exposed to low numbers of the same phage, a temporary defence was induced that used an immune response known as a CRISPR. Although costly when in use, in the absence of viruses the CRISPR response can lie dormant until required. The low overhead cost of this immune response has little impact on the long term health of the bacteria making it ideal for use in commercial applications. Working in a similar way to a vaccine, bacteria could be 'pre-loaded' with CRISPR immune responses for multiple different phages. This is better for the health of the bacteria and results in higher product yields as well as protecting the culture in the event of infection with a range of viruses. The research indicates that parasite exposure is likely to be a key factor in driving the evolution of permanent versus inducible -- or temporary -defences in nature. This suggests that organisms living together in large populations, or parasite-rich conditions, are more likely to evolve permanent defences, whereas low parasite conditions select for inducible defences.