Some lactic acid bacteria utilize the potential energy developed by the accumulation of fermentation products in the cell to drive nutrient transport in a similar manner to antiport. Instead of H+ or Na+, a fermentation product is exchanged with its precursor and this system is therefore referred to as the precursorlproduct antiport (Figure 3.6). A malate/lactate antiport system is known in species of Lactobacillus, Streptococcus, Leuconostoc and Pediococcus. They generate a proton motive force fermenting rnalate to lactate through the well-documented malolactic fermentation pathway (Section 8.4.6).