Cell wall biogenesis; teichuronic acid biosynthesis. By phosphate starvation, via the PhoP/PhoR two-component regulatory system. The nature of the anionic polymer present in the cell wall of B.subtilis depends on phosphate availability. Under phosphate-replete growth conditions teichoic acids are present, whereas under phosphate-depleted conditions, at least part of the wall teichoic acid is replaced with teichuronic acid, a non-phosphate containing anionic polymer. The synthesis of teichuronic acid is accompanied by degradation of teichoic acid and reutilization of liberated phosphate for other cellular processes such as nucleic acid synthesis. Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 4 subfamily.