The first part of this book provides an inventory of the concepts necessary to understand the metabolism of bacteria, the methods of identification and the alterations related to the development of certain bacteria. It is accompanied by an exhaustive bibliography that allows the reader to deepen some of the aspects developed in the book. The second part presents from a practical point of view the impact of bacteria on the qualities of the wine, the control of malolactic fermentation and the consequences related to poor management of this fermentation. Many practical situations are described, as well as a range of problems encountered during malolactic fermentation. The different strategies for carrying out this fermentation are outlined. Lactic acid bacteria in oenology is aimed at all specialists in the sector, oenologists, technicians and scientists, as well as students.