GneZ, a UDP-GlcNAc 2-Epimerase, Is Required for S-Layer Assembly and Vegetative Growth of Bacillus anthracis

Bacillus anthracis , the causative agent of anthrax, forms an S-layer atop its peptidoglycan envelope and displays S-layer proteins andBacillus S-layer-associated (BSL) proteins with specific functions to support cell separation of vegetative bacilli and growth in infected mammalian hosts. S-layer and BSL proteins bind via the S-layer homology (SLH) domain to the pyruvylated secondary cell wall polysaccharide (SCWP) with the repeat structure [→4)-β-ManNAc-(1→4)-β-GlcNAc-(1→6)-α-GlcNAc-(1→]n , where α-GlcNAc and β-GlcNAc are substituted with two and one galactosyl residues, respectively.B. anthracis gneY (BAS5048) andgneZ (BAS5117) encode nearly identical UDP-GlcNAc 2-epimerase enzymes that catalyze the reversible conversion of UDP-GlcNAc and UDP-ManNAc. UDP-GlcNAc 2-epimerase enzymes have been shown to be required for the attachment of the phage lysin PlyG with the bacterial envelope and for bacterial growth. Here, we asked whethergneY andgneZ are required for the synthesis of the pyruvylated SCWP and for S-layer assembly. We show thatgneZ , but notgneY , is required forB. anthracis vegetative growth, rod cell shape, S-layer assembly, and synthesis of pyruvylated SCWP. Nevertheless, inducible expression ofgneY alleviated all the defects associated with thegneZ mutant. In contrast to vegetative growth, neither germination ofB. anthracis spores nor the formation of spores in mother cells required UDP-GlcNAc 2-epimerase activity.