The Gospel of Thomas (NHC II, 2): a fragmentary writing, scholarly readership and discursive imagination
Microorganisms are involved in the production of many foods we consume every day, including cheese, yogurt, and other dairy products. One of the most important industrial microbes is Lactococcus lactis, a bacterium that has been used for centuries in dairy fermentation and is also becoming a valuable tool in biotechnology. For a long time, scientists believed that most genetic regulation depended mainly on proteins. However, it is now clear that RNA molecules can also act as regulators, helping cells respond quickly to changes in their environment. Despite their importance, these RNA-based regulatory molecular mechanisms remain poorly understood in L. lactis. In this thesis, we explored how noncoding RNA molecules influence the behavior of this bacterium. We identified an RNA element that can be used as a molecular switch to control gene expression, providing a new tool for genetic engineering. We also described the landscape of RNA-binding proteins of L. lactis as well as the first sRNA-binding protein in this organism, revealing an important component of its RNA-based regulatory network.Finally, we investigated an sRNA called CisR, whose expression increases upon cold exposure. Our results show that CisR could help the bacterium adjust its fructose metabolism when temperatures change. CisR represses the repressor of the fructose uptake system, which may favor fructose uptake and provide protection under low temperature conditions. This finding provides further insight into how L. lactis adapts to environmental stress through RNA-mediated regulation.