One of the survival strategies used by planktonic bacteria when under stress is to encase their community within an extracellular matrix composed of biopolymers, such as polysaccharides, DNA, and proteins, thereby forming a biofilm that adheres to surfaces and interfaces (1⇓–3). The chemical structure of the polysaccharides involved varies widely among different species of bacteria, but one structure that is common to many medically important biofilm-forming bacteria (both Gram-negative and Gram-positive) is that of partially de- N -acetylated poly-β-1,6- N -acetyl-d-glucosamine (dPNAG) (Fig. 1 A ) (4). This polymer differs from the more biologically familiar chitin in its 1,6 rather than 1,4 linkage pattern, but would be similarly insoluble were it not for the partial de- N -acetylation that exposes highly polar ammonium substituents on the chain. Similarly, chitin can be converted to a partially de- N -acetylated form known as chitosan. In PNAS, Little et al. (5) use structural, computational, and functional studies to explore the role of PgaB, a de- N -acetylase enzyme that is known to be critical in both the tailoring and extracellular export of the dPNAG component of biofilms produced by Escherichia coli . Fig. 1. ( A ) The structure of dPNAG. ( B ) The synthase-dependent pathway of dPNAG production and export encoded by pgaABCD in E. coli . In E. coli dPNAG is produced by a synthase-dependent pathway, one of three main mechanisms by which bacteria produce and secrete polysaccharides (6) [the other two are the Wzx/Wzy-dependent and the ATP-binding cassette (ABC) transporter-dependent pathways (6, 7)]. Common components of synthase-dependent pathways are an inner membrane-spanning synthase protein, an inner membrane bis-(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) receptor … [↵][1]1To whom correspondence should be addressed. Email: withers{at}chem.ubc.ca. [1]: #xref-corresp-1-1