Biology subjects

Hooper, L.

Publications and source records attributed to Hooper, L..

5 recordsLinked to original sources

bioRxiv2026

Salmonella lipopolysaccharide stimulates uptake of long-chain fatty acids in the small intestine

Enteric bacterial pathogens profoundly alter intestinal physiology during infection, yet their effects on host lipid metabolism remain poorly understood. Using mass spectrometry lipidomics, we found that infection of the mouse intestine with the bacterial pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) stimulates uptake of long-chain fatty acids by small intestinal epithelial cells. This response coincided with increased expression of epithelial genes involved in lipid uptake and transport and required the long-chain fatty acid transporter CD36. Fatty acid uptake was triggered by S. Typhimurium lipopolysaccharide (LPS) and was impaired by bacterial mutations that alter LPS acyl chains. Mechanistically, S. Typhimurium induced lipid absorption through myeloid cell Toll-like receptor 4, a receptor for LPS. Escherichia coli, a related commensal bacterium, also induced intestinal lipid absorption through LPS, although to a lesser extent than S. Typhimurium. Finally, disruption of long-chain fatty acid absorption impaired host defense during bacterial stimulation, suggesting that bacteria-induced lipid uptake contributes to protection against enteric infection. Together, these findings identify LPS from Gram-negative intestinal bacteria as a key regulator of dietary lipid uptake by the intestinal epithelium. Significance StatementThe intestinal lining absorbs nutrients while also detecting bacteria that enter with food, but how these two functions intersect during infection is poorly understood. Salmonella is a food-borne bacterial pathogen that infects humans. By studying mice, we found that Salmonella infection rapidly enhances absorption of dietary lipids by intestinal epithelial cells. This response was triggered when immune cells beneath the gut lining detected lipopolysaccharide, a molecule in the outer coat of many Gram-negative bacteria. In mice with defective lipid absorption, more Salmonella spread beyond the intestine, suggesting that lipid uptake contributes to host defense. These findings reveal a previously unappreciated link between microbial sensing, nutrient absorption, and defense against intestinal infection.

microbiology↗

bioRxiv2026

B3GNT7 regulates mucin glycosylation and protects against colitis and infection

Mucus covers and protects colonic epithelial cells. Mucus is mainly composed of heavily O-glycosylated proteins called mucins, and disruption of normal mucin glycosylation occurs in ulcerative colitis (UC). Mucin-2 (MUC2) is the major colonic mucin, and MUC2 O-glycans are often extended with sulfated polyLacNAc, also known as keratan sulfate (KS). The GlcNAc residues in KS are added by B3GNT family members. B3GNT7 is highly expressed in the colon, and B3GNT7 expression is dramatically reduced in UC. However, the function of B3GNT7 in colonic physiology is unexplored. Here we show that B3gnt7 is a key player in colonic physiology through its function in controlling the structure of mucus glycans. We found that B3GNT7 prefers to extend a sulfated acceptor substrate and is required for production of polyLacNAc-modified mucus in a human goblet cell model. In vivo, B3GNT7 regulates Muc2, Muc13, and Muc17 O-glycosylation. Intestinal B3GNT7 deficiency increases susceptibility to colitis and enteric infection in mice, showing that B3GNT7-dependent glycosylation confers protective properties to colonic mucus. Taken together, these results demonstrate that B3GNT7 has a function distinct from other B3GNT family members and is critical for maintaining colonic homeostasis. SIGNIFICANCE STATEMENTUlcerative colitis is a chronic inflammatory bowel disease that affects 5 million people globally. The colonic mucus layer forms a protective barrier over colonic epithelial cells and is disrupted in ulcerative colitis. Mucus is composed of mucin proteins decorated by carbohydrates, called glycans. Glycans confer protective properties to the mucus barrier, and mucin glycans change in ulcerative colitis. B3GNT7 is an enzyme that elongates glycans and is downregulated in ulcerative colitis. In this study, we use in vitro and in vivo models to demonstrate that B3GNT7 regulates colonic mucus glycans and protects mice against colitis and infection. Our findings provide molecular insight into the contributions of B3GNT7-dependent glycans to colonic homeostasis.

biochemistry↗

bioRxiv2023

Susceptible bacteria survive antibiotic treatment in the mammalian gastrointestinal tract without evolving resistance

In vitro systems have provided great insight into the mechanisms of antibiotic resistance. Yet, in vitro approaches cannot reflect the full complexity of what transpires within a host. As the mammalian gut is host to trillions of resident bacteria and thus a potential breeding ground for antibiotic resistance, we sought to better understand how gut bacteria respond to antibiotic treatment in vivo. Here, we colonized germ-free mice with a genetically barcoded antibiotic pan-susceptible Escherichia coli clinical isolate and then administered the antibiotic cefepime via programmable subcutaneous pumps which allowed for closer emulation of human parenteral antibiotic pharmacokinetics/dynamics. After seven days of antibiotics, we were unable to culture E. coli from feces. We were, however, able to recover barcoded E. coli from harvested gastrointestinal (GI) tissue, despite high GI tract and plasma cefepime concentrations. Strikingly, these E. coli isolates were not resistant to cefepime but had acquired mutations - most notably in the wbaP gene, which encodes an enzyme required for the initiation of the synthesis of the polysaccharide capsule and lipopolysaccharide O antigen - that increased their ability to invade and survive within intestinal cells, including cultured human colonocytes. Further, these E. coli mutants exhibited a persister phenotype when exposed to cefepime, allowing for greater survival to pulses of cefepime treatment when compared to the wildtype strain. Our findings highlight a mechanism by which bacteria in the gastrointestinal tract can adapt to antibiotic treatment by increasing their ability to persist during antibiotic treatment and invade intestinal epithelial cells where antibiotic concentrations are substantially reduced.

microbiology↗

bioRxiv2022

Immune checkpoint blockade induces gut microbiota translocation that augments extraintestinal anti-tumor immunity

Gut microbiota are critical for effective immune checkpoint blockade therapy (ICT) for cancer. The mechanisms by which gut microbiota augment extraintestinal anti-cancer immune responses, however, are largely unknown. Here, we find that ICT induces translocation of specific endogenous gut microbiota into secondary lymphoid organs and subcutaneous melanoma tumors. Mechanistically, gut microbiota activated dendritic cells (DCs) traffic a selective subset of gut bacteria to mesenteric lymph nodes (MLN) and promote optimal anti-tumor T-cell responses in both the tumor draining lymph nodes (TDLN) and the primary tumor. Antibiotic treatment resulted in decreased gut microbiota translocation into MLN and TDLN, diminished polyfunctional effector CD8+ T cell responses, and attenuated response to ICT. Our findings illuminate a key mechanism by which gut microbiota promote extraintestinal anti-cancer immunity. One sentence summaryFollowing immune checkpoint blockade therapy, dendritic cells traffic gut microbiota into secondary lymphoid organs, promoting optimal extraintestinal anti-cancer immunity.

immunology↗

bioRxiv2020

Impact of bead-beating intensity on microbiome recovery in mouse and human stool: Optimization of DNA extraction

DNA extraction methods play an important role in the acquisition of accurate and reproducible 16S sequencing data in microbiome studies. In this study, we assessed the impact of bead-beating intensity during DNA extraction on microbiome recovery in mouse and human stool. We observed a higher DNA yield, better DNA integrity, higher Shannons entropy and Simpsons index in samples beaten for 4 and 9 minutes as compared to unbeaten samples. 16S sequencing data showed that bead beating has a statistically-significant (p<0.05) impact on the recovery of many clinically relevant microbes that live in the mouse and human gut, including Bifidobacterium, Sutterella and Veillonella. It was observed that 4 minutes of bead beating promotes recovery of about 70% of OTUs in mouse and human stool, while the remaining 30% requires longer bead beating. In conclusion, our study indicates adjustments in bead beating treatment based on the composition of the specimen and the targeted bacteria.

microbiology↗