A four-gene operon in Bacillus cereus produces two rare spore-decorating sugars

Abstract

Bacterial glycan structures on cell surfaces are critical for cell-cell recognition and adhesion and in host-pathogen interactions. Accordingly, unraveling the sugar composition of bacterial cell surfaces can shed light on bacterial growth and pathogenesis. Here, we found that two rare sugars with a 3--methyl-6-deoxyhexose structure were linked to spore glycans in ATCC 14579 and ATCC 10876. Moreover, we identified a four-gene operon in ATCC 14579 that encodes proteins with the following sequential enzyme activities as determined by mass spectrometry and one- and two-dimensional NMR methods: CTP:glucose-1-phosphate cytidylyltransferase, CDP-Glc 4,6-dehydratase, NADH-dependent SAM:-methyltransferase, and NADPH-dependent CDP-3--methyl-6-deoxyhexose 4-reductase. The last enzyme predominantly yielded CDP-3--methyl-6-deoxygulose (CDP-cereose) and likely generated a 4-epimer CDP-3--methyl-6-deoxyallose (CDP-cillose). Some members of the group produce CDP-3--methyl-6-deoxy sugars for the formation of cereose-containing glycans on spores, whereas others such as do not. Gene knockouts of the-methyltransferase and the 4-reductase confirmed their involvement in the formation of cereose-containing glycan on spores. We also found that cereose represented 0.2-1% spore dry weight. Moreover, mutants lacking cereose germinated faster than the wild type, yet the mutants exhibited no changes in sporulation or spore resistance to heat. The findings reported here may provide new insights into the roles of the uncommon 3--methyl-6-deoxy sugars in cell-surface recognition and host-pathogen interactions of the genus .

Expression of Bacillus cereus Virulence-Related Genes in an Ocular Infection-Related Environment

“…EntD regulates virulence genes and genes with virulence-associated functions such as those involved in cell metabolism, cell structure, antioxidation, motility, and toxin production [52]. EntD regulates a four gene operon that synthesizes rare glycans present on the spore surface important for receptor recognition [53]. EntD is also involved in the regulation of proteins associated with the bacterial surface and are important in motility and biofilm formation.…”

Contributions of crust proteins to spore surface properties in Bacillus subtilis

“…The discoveries of the sugars anthrose and cereose on the surface of B. anthracis and B. cereus spores, respectively, implies that the carbohydrate profiles of spores can be highly species‐specific (Daubenspeck et al , ; Maes et al , ; Li et al , ). These properties are especially important for understanding pathogenic spore forming bacteria and could significantly influence strategies deployed for their elimination.…”

“…Nevertheless, several species appear to synthesize at least one species‐specific sugar during sporulation; i.e. anthrose in B. anthracis , cereose in B. cereus and quinovose in B. subtilis (Daubenspeck et al , ; Faille et al , ; Li et al , ). Carbohydrate production during sporulation in B. subtilis is dependent on σ K , which controls expression of the spore polysaccharide synthesis ( sps ) operon (Eichenberger et al , ).…”

Galactosylation of the Secondary Cell Wall Polysaccharide of Bacillus anthracis and Its Contribution to Anthrax Pathogenesis

“…Similar to UDP-GlcNAc 2-epimerase, the genome of B. anthracis also includes two genes, galE1 and galE2, for UDP-Glc 4-epimerase, an enzyme that catalyzes the reversible interconversion of UDP-Glc and UDP-Gal (19). One of these two genes, galE2, is expressed only during B. anthracis sporulation, providing UDP-Gal and UDP-GalNAc substrates for the glycosylation of BclA, an exosporium protein in the outer spore nap that is produced by all members of the B. cereus sensu lato group (21,(43)(44)(45). In contrast, galE1 is only expressed during vegetative growth and provides UDP-Gal for the galactosylation of the SCWP in B. anthracis.…”