Hexosyltransferase involved in N-glycan biosynthetic pathway that takes place under low-salt conditions (1.75 M instead of 3.4 M). Participates in the formation of the tetrasaccharide present at 'Asn-532' of S-layer glycoprotein Csg, consisting of a sulfated hexose, 2 hexoses and rhamnose. Involved in the addition of sugar 3 to the disaccharide-charged dolichol phosphate in the tetrasaccharide. Protein modification; protein glycosylation. Cell surface structure biogenesis; S-layer biogenesis. Impaired formation of the tetrasaccharide present at 'Asn-532' of S-layer glycoprotein Csg. No effect on 'Asn-47' and 'Asn-117' glycosylation of S-layer glycoprotein Csg. Belongs to the glycosyltransferase group 1 family.