The Peptidoglycan Sacculus of Myxococcus xanthus Has Unusual Structural Features and Is Degraded during Glycerol-Induced Myxospore Development

Abstract

ABSTRACT Upon nutrient limitation cells of the swarming soil bacterium Myxococcus xanthus form a multicellular fruiting body in which a fraction of the cells develop into myxospores. Spore development includes the transition from a rod-shaped vegetative cell to a spherical myxospore and so is expected to be accompanied by changes in the bacterial cell envelope. Peptidoglycan is the shape-determining structure in the cell envelope of most bacteria, including myxobacteria. We analyzed the composition of peptidoglycan isolated from M. xanthus . While the basic structural elements of peptidoglycan in myxobacteria were identical to those in other gram-negative bacteria, the peptidoglycan of M. xanthus had unique structural features. meso - or ll -diaminopimelic acid was present in the stem peptides, and a new modification of N -acetylmuramic acid was detected in a fraction of the muropeptides. Peptidoglycan formed a continuous, bag-shaped sacculus in vegetative cells. The sacculus was degraded during the transition from vegetative cells to glycerol-induced myxospores. The spherical, bag-shaped coats isolated from glycerol-induced spores contained no detectable muropeptides, but they contained small amounts of N -acetylmuramic acid and meso -diaminopimelic acid.