Do Gram-negatives produce cellulose or not?
New insights into the chemical composition of bacterial cellulose reveals that it is substantially different from the polymer found in plants.
- Bacterial cellulose from E. coli and Salmonella found to be chemically different from plant cellulose
- Solid state NMR revealed that bacterial cellulose has a zwitterionic phosphoethanolamine modification
- The bcsEFG operon, present in many Gram-negatives is responsible for the modification
We were totally blind, or so it seems. A new paper in Science has probed the structure of bacterial cellulose and revealed that it's not as we first thought. The research team led by Regine Hengge and Lynette Cegelski used NMR to look at the structure of bacterial cellulose and astonishingly found that throughout the years of research into this important polymer, we had missed something. They saw that bacterial cellulose is modified to possess a phosphoethanolamine group. While the initial research was carried out in E. coli and Salmonella, the team expanded their search and found that this modification was likely present in many γ- and β-proteobacteria. The notable exception was Komagataeibacter xylinus which produces much more cellulose that other members of the phylum. The research team pointed out that production of Phosphoethanolamine cellulose by this species would lead to a depletion of the headgroups of the phospholipid membrane and the bcsEFG operon responsible for the modification is understandably absent.
This is an incredible finding. Seeing something that was right under our noses the first time ever. It seems that calcofluor assays have been lying to us or at least, masking the truth. I may be completely biased here, given that I work at MAX IV Laboratory, but I wonder what we would see if biofilms were put in front of a state of the art synchrotron beam?
Cellulose is a major contributor to the chemical and mechanical properties of plants and assumes structural roles in bacterial communities termed biofilms. We find that Escherichia coli produces chemically modified cellulose that is required for extracellular matrix assembly and biofilm architecture. Solid-state nuclear magnetic resonance spectroscopy of the intact and insoluble material elucidates the zwitterionic phosphoethanolamine modification that had evaded detection by conventional methods. Installation of the phosphoethanolamine group requires BcsG, a proposed phosphoethanolamine transferase, with biofilm-promoting cyclic diguanylate monophosphate input through a BcsE-BcsF-BcsG transmembrane signaling pathway. The bcsEFG operon is present in many bacteria, including Salmonella species, that also produce the modified cellulose. The discovery of phosphoethanolamine cellulose and the genetic and molecular basis for its production offers opportunities to modulate its production in bacteria and inspires efforts to biosynthetically engineer alternatively modified cellulosic materials.
Phosphoethanolamine cellulose: A naturally produced chemically modified cellulose
Wiriya Thongsomboon, Diego O. Serra, Alexandra Possling, Chris Hadjineophytou, Regine Hengge, Lynette Cegelski
Science 19 Jan 2018: Vol. 359, Issue 6373, pp. 334-338