Summary 14Prokaryotes use a mechanism called priming to update their CRISPR immunological memory to rapidly counter 15 revisiting, mutated viruses and plasmids. Here we have determined how new spacers are produced and 16 selected for integration into the CRISPR array during priming. We show that Cas3 couples CRISPR interference 17 to adaptation by producing DNA breakdown products that fuel the spacer integration process in a two-step,

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afe food is vital for everyone and controlling food safety requires the combined efforts of all stakeholders in the whole food chain, from primary production to food processing and retail to the consumer side. However, inadequate adherence to these combined efforts at any stage of food production can result in unsafe food. The World Health Organization (WHO) estimated that between 420 and 960 million foodborne illnesses are contracted each year, leading to between 310,000 and 600,000 deaths annually (Mehlhorn, 2015). Zooming in to the Netherlands, there were 553,000 estimate cases of foodborne illness in 2020 with 76 fatal cases (Benincà et al., 2021). Both from a public safety as well as an economic perspective, unsafe foods are a significant burden on society.However, controlling the safety of food is not an easy task and this is complicated by challenges along the food chain. Food products can be contaminated along the food production chain and food products are often able to support the survival and/or growth of microorganisms. Foodborne viruses and bacterial agents are a major cause of foodborne infections and illnesses, ranging from mild gastroenteritis to life-threatening bacterial infections (Cliver & Riemann, 2011; O'Shea et al., 2019). It is therefore extremely important that the presence of foodborne pathogens in foods is under strict control. Foods usually undergo processing steps in which the bacterial load is reduced, such as pasteurization or other (non) thermal treatments and/or the use of preservatives. For the products to remain safe during the rest of manufacturing, adequate environmental hygiene in production facilities is mandatory to significantly reduce the chance of contamination later in the process. This means thorough cleaning and disinfection in production areas, food storage, and transport. Lastly, poor personal hygiene practices of food handlers and consumers pose another risk for unsafe food (Schneider et al., 2010). Simple precautions like hand washing and prevention of cross-contamination in cutting and handling of raw foods is important to reduce the risk of foodborne illness (Hillers et al., 2003). Listeria monocytogenes: a dangerous foodborne pathogenThe relevance of controlling food pathogens such as Listeria monocytogenes came once again to the forefront of worldwide news in June of 2017. The number of cases of patients suffering from L. monocytogenes infection started to grow rapidly in South Africa, which would eventually lead to the world's largest outbreak of L. monocyto-1.2. L. monocytogenes: a dangerous foodborne pathogen 1 3 genes with 1,060 laboratory-confirmed cases of listeriosis and 216 deaths reported by the National Institute of Communicable Diseases (NICD), in the period between January 2017 to July 17 2018 (Smith et al., 2019). Although outbreaks of L. monocytogenes are quite rare, the risk of severe or lethal outcomes is large due to the high mortality rate of 13.0 % in 2020 over the whole EU (European Food Safety Authority, 2021). This makes that this foodbor...