Relevance of Trehalose in Pathogenicity: Some General Rules, Yet Many Exceptions

Trehalose, a natural disaccharide, consists of two glucose molecules linked by an a, a-1,1-glucoside bond. Apart from its function as a reserve carbohydrate, trehalose is known for its role as a stress protectant in many organisms across kingdoms. It is present in plants, invertebrates, fungi, and prokaryotes, but not in mammals. Despite its well-known protective roles against desiccation, freezing, starvation, and osmotic stress [1], trehalose has escaped categorization into a specific biological pathway. Interestingly, a role for its metabolism is emerging in the establishment of virulence traits in distantly related microbial species. In general, although notable exceptions exist, the absence of a complete trehalose metabolism apparatus is associated with a lower pathogenic potential. The mechanisms involved, however, are less clear. Pathogens have engineered several distinct trehaloseassociated mechanisms that contribute to cell morphogenesis, cell wall integrity, regulation of metabolism, and evasion from the host immune response.