PelX is a UDP-N-acetylglucosamine C4-epimerase involved in Pel polysaccharide-dependent biofilm formation — Pel biosynthesis requires a UDP-GlcNAc C4-epimerase — PelX is a UDP-N-acetylglucosamine C4-epimerase involved in Pel polysaccharide–dependent biofilm formation — EDITORS' PICK: Pel biosynthesis requires a UDP-GlcNAc C4-epimerase