And these linkages are known as cross linkages and they're the green linkages shown in this diagram. So the peptaglyc and cell wall consists of long sugar chains that are connected by cross linkages between the short peptides. So this blue peptide here is connected to this blue peptide of the Jason polysaccharide chain via this five peptide. So the pentapeptide short protein component. Now the question is what exactly is the reaction by which the bacterial cells actually build these cross linkages in the first place? Well this is the reaction that is described on the board.