The aim of this work is to search for genes involved in the regulation global responses in Lactococcus lactis. To achieve our objective, we propose to make several transcriptional fusions of promoters from cloned L. lactis genes to promoterless reporter genes (cat, lacLM, lacZ, gus, lacG) and inserted them in the lactococcal chromosome. One derivative with more than one fusion will be used to obtain a collection of insertional mutants by using a Ts-system based on an IS element (ISS1) developed in the host institution. Mutants with higher resistance to Cm or with less intense blue colour will be selected and the mutated gene will be transferred to the strains containing the other fusions in order to analyze its ability to regulate them. Further characterization of pleiotropic regulators will be made on the molecular level regarding the structure and expression of these regulatory genes and its targets.