Expansion of the Spore Surface Polysaccharide Layer in Bacillus subtilis by Deletion of Genes Encoding Glycosyltransferases and Glucose Modification Enzymes

• Published in: Journal of bacteriology 2019-10, Vol.201 (19), p.1
• Main Authors: Shuster, Bentley, Khemmani, Mark, Nakaya, Yusei, Holland, Gudrun, Iwamoto, Keito, Abe, Kimihiro, Imamura, Daisuke, Maryn, Nina, Driks, Adam, Sato, Tsutomu, Eichenberger, Patrick
• Format: Article
• Language: English
• Subjects: Bacillus subtilis; Bacteriology; Carbohydrates; Electron microscopy; Enzymes; Gene clusters; Genes; Glucose; Glucose-1-phosphate; Hydrophobicity; Microscopy; Morphology; Mutation; Phenotypes; Polysaccharides; Properties (attributes); Ruthenium; Ruthenium red; Saccharides; Scanning electron microscopy; Spores; Sporulation; Spotlight; Staining; Surface properties; Synthesis; Transmission electron microscopy
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/jb.00321-19

Polysaccharides (PS) decorate the surface of dormant endospores (spores). In the model organism for sporulation, , the composition of the spore PS is not known in detail. Here, we have assessed how PS synthesis enzymes produced during the late stages of sporulation affect spore surface properties. Using four methods, bacterial adhesion to hydrocarbons (BATH) assays, India ink staining, transmission electron microscopy (TEM) with ruthenium red staining, and scanning electron microscopy (SEM), we characterized the contributions of four sporulation gene clusters, , , - , and , on the morphology and properties of the crust, the outermost spore layer. Our results show that all mutations in the operon result in the production of spores that are more hydrophobic and lack a visible crust, presumably because of reduced PS deposition, while mutations in and the cluster noticeably expand the PS layer. In addition, mutant spores exhibit a crust with an unusual weblike morphology. The hydrophobic phenotype from mutant spores was partially rescued by a second mutation inactivating any gene in the operon. While , and are paralogous genes, all encoding glucose-1-phosphate nucleotidyltransferases, each paralog appears to contribute in a distinct manner to the spore PS. Our data are consistent with the possibility that each gene cluster is responsible for the production of its own respective deoxyhexose. In summary, we found that disruptions to the PS layer modify spore surface hydrophobicity and that there are multiple saccharide synthesis pathways involved in spore surface properties. Many bacteria are characterized by their ability to form highly resistant spores. The dormant spore state allows these species to survive even the harshest treatments with antimicrobial agents. Spore surface properties are particularly relevant because they influence spore dispersal in various habitats from natural to human-made environments. The spore surface in (crust) is composed of a combination of proteins and polysaccharides. By inactivating the enzymes responsible for the synthesis of spore polysaccharides, we can assess how spore surface properties such as hydrophobicity are modulated by the addition of specific carbohydrates. Our findings indicate that several sporulation gene clusters are responsible for the assembly and allocation of surface polysaccharides. Similar mechanisms could be modulating the dispersal of infectious spore-forming bacteria.