“…Here, we mimic the horizontal gene transfer event, the first step in the successful acquisition of new functionality in this evolutionary process, by introducing the histidine decarboxylation pathway of the yoghurt bacterium Streptococcus thermophilus CHCC1524 (16,26) in the cheese bacterium Lactococcus lactis and analyzing the beneficial effects for the receiving organism. The gene cluster encoding the pathway consists of the histidine decarboxylase gene hdcA, the histidine/ histamine exchanger gene hdcP, and the HdcA maturation factor gene hdcB and is transcribed as one mRNA, thus forming one operon (16,26). Recently, the complete hdcA-hdcP-hdcB operon was functionally expressed in L. lactis as part of a study demonstrating the function of HdcB in the cleavage of the HdcA proenzyme, an essential step in the formation of the pyruvoyl group cofactor (27,28).…”