Spore formation in the Gram negative bacterium, Myxococcus xanthus
Final Report Abstract
Spore differentiation in the Gram-negative bacterium, Myxococcus xanthus, involves rearragment of a rod-shaped cell into a spherical spore in a process that involves degradation of the peptidoglycan and syntheis of a novel stress-bearing cell wall on the on the outer surface of the outer membrane. This project examined compostion of the spore wall and determined that it consists primarily of 4- and 3-linked galactosamine (GalN), small amounts of 4-linked glucose (Glc), and glycine (Gly). None of the components derive from M. xanthus extracellular polysachrides or O-Antigen. We demonstrated that these components are synthesized and secreted to the cell surface by the Exo protein complex. This complex shares homology to Wzc capusle synthesis machinery, and consistent with this proposed function, we demonstrated that the initiating transferase, ExoE, catalyzes transfer of GalN to und-PP. We further showed that a second complex of proteins, NsfA-B, when produced in E. coli, spans the cell envelope with NfsD, G, E fractionating with the cytomplasmic membrane and NfsA, B and C fractionating with the outer membrane. The Nfs complex likely functions to convert the capusle like polysacharides secreted by the Exo complex into a stress-bearing spore wall by alterning the chain length of the polysacardies to enable efficint glycan cross-linking. We propose the M. xanthus spore wall represents a novel peptide-glycan in which GalN polymers are crosslinked by glycine peptides; this structure remains to be demonstrated.
Publications
- “The analysis of programmed cell death and sporulation in the Myxococcus xanthus developmental program.” (2013) Ph.D. Thesis, Phillip University Marburg
Holkenbrink, Carina
- Synthesis and assembly of a novel glycan layer in Myxococcus xanthus spores. (2014) Journal of Biological Chemistry. 289:32364-78
Holkenbrink, C., Hoiczyk, E., Kahnt, J., and P.I. Higgs
(See online at https://doi.org/10.1074/jbc.M114.595504)
