Regulates the length of the LPS O-antigen polysaccharide chain. Stops the polymerization of the chain by phosphorylating and then methylating the phosphate on the terminal sugar. This terminal modification is essential for export of the O-antigen across the inner membrane. WbdD is also required for correct localization of the WbdA mannosyltransferase. 3-O-phospho-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-[alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)](n)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-GlcNAc-di-trans,octa-cis-undecaprenyl diphosphate + S-adenosyl-L-methionine = 3-O-methylphospho-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-[alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)](n)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-GlcNAc-di-trans,octa-cis-undecaprenyl diphosphate + S-adenosyl-L-homocysteine alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-[alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)](n)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-GlcNAc-di-trans,octa-cis-undecaprenyl diphosphate + ATP = 3-O-phospho-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-[alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)](n)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-Man-(1->3)-alpha-D-GlcNAc-di-trans,octa-cis-undecaprenyl diphosphate + ADP + H(+) Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Interacts with WbdA. Belongs to the WbdD family.