Salmonella Degrades the Host Glycocalyx Leading to Altered Infection and Glycan Remodeling

Abstract

Complex glycans cover the gut epithelial surface to protect the cell from the environment. Invasive pathogens must breach the glycan layer before initiating infection. While glycan degradation is crucial for infection, this process is inadequately understood. Salmonella contains 47 glycosyl hydrolases (GHs) that may degrade the glycan. We hypothesized that keystone genes from the entire GH complement of Salmonella are required to degrade glycans to change infection. This study determined that GHs recognize the terminal monosaccharides (N-acetylneuraminic acid (Neu5Ac), galactose, mannose, and fucose) and significantly (p < 0.05) alter infection. During infection, Salmonella used its two GHs sialidase nanH and amylase malS for internalization by targeting different glycan structures. The host glycans were altered during Salmonella association via the induction of N-glycan biosynthesis pathways leading to modification of host glycans by increasing fucosylation and mannose content, while decreasing sialylation. Gene expression analysis indicated that the host cell responded by regulating more than 50 genes resulting in remodeled glycans in response to Salmonella treatment. This study established the glycan structures on colonic epithelial cells, determined that Salmonella required two keystone GHs for internalization, and left remodeled host glycans as a result of infection. These data indicate that microbial GHs are undiscovered virulence factors.

Implication of Sialidases in Salmonella Infection: Genome Release of Sialidase Knockout Strains from Salmonella enterica Serovar Typhimurium LT2

“…and other foodborne pathogens. These seven sialidase and one sialic acid transporter mutant strain were constructed in the Weimer Laboratory (UC Davis, Davis, CA, USA) (6) as described by Datsenko and Wanner (7). Cultures were grown on 1.5% Luria–Bertani agar (Difco, Franklin Lakes, NJ, USA), with 10 µg/mL of chloramphenicol at 37°C, and then lysed (8).…”

Glycan‐metabolizing enzymes in microbe–host interactions: the Streptococcus pneumoniae paradigm

“…Commensal and pathogenic microbes often take advantage of host-glycan abundance and importance by targeting them for the purposes of nutrition, cell attachment, invasion, and/or immunomodulation [2]. Many of the best-studied examples of the relationship between microbial glycan processing and the host-microbe interaction relate to intestinal microbes that degrade ingested and/or host-derived glycans [2][3][4][5][6][7]; however, other body sites that are rich in carbohydrates are also targeted by microbes, such as the oral cavity [8,9], genitourinary tract [10], and respiratory system [11]. The majority of respiratory pathogens appears to be relatively restricted in their carbohydrate usage, but Streptococcus pneumoniae stands out by its Abbreviations angle X-ray scattering; SBP, solute binding protein; STM, signature-tagged mutagenesis; UGL, unsaturated glucuronyl hydrolase; Xyl, xylose; GlcA, unsaturated D-glucuronic acid.…”

Amylases and Their Importance during Glycan Degradation: Genome Sequence Release of Salmonella Amylase Knockout Strains

“…That group also demonstrated that each of the four mutant amylase strains (Δ malS, Δ amyA, Δ glgX , and Δ glgB mutants) had different invasion phenotypes during the in vitro infection of differentiated colonic epithelial cells (Caco-2) (1); however, only the Δ malS mutant significantly ( P < 0.05) reduced adhesion and invasion during infection that were comparable to those seen with a nonpathogenic Salmonella strain (1). …”