Research Publications (Food Safety)

Initial attachment and subsequent colonization of the intestinal epithelium comprise critical events allowing enteric pathogens to survive and express their pathogenesis. In enterotoxigenic Escherichia coli (ETEC), these are mediated by a long proteinaceous fiber termed type IVb pilus (T4bP). We have reported that the colonization factor antigen/III (CFA/III), an operon-encoded...

While the structure and regulatory networks that govern type-six secretion system (T6SS) activity of Vibrio cholerae are becoming increasingly clear, we know less about the role of T6SS in disease. Under laboratory conditions, V. cholerae uses T6SS to outcompete many Gram-negative species, including other V. cholerae strains and human commensal...

Novel reassortant avian influenza H7N9 virus and pandemic 2009 H1N1 (H1N1pdm) virus cause human infections, while avian H7N2 and swine H1N1 virus mainly infect birds and pigs, respectively. There is no robust in vitro model for assessing the infectivity of emerging viruses in humans. Based on a recently established method,...

Sensing and responding to environmental changes is essential for bacteria to adapt and thrive, and nucleotide-derived second messengers are central signaling systems in this process. The most recently identified bacterial cyclic dinucleotide second messenger, 3′, 3′-cyclic GMP-AMP (cGAMP), was first discovered in the El Tor biotype of Vibrio cholerae. The...

AGRICULTURAL SCIENCES Correction for “Ion-beam irradiation, gene identification, and marker-assisted breeding in the development of low-cadmium rice,” by Satoru Ishikawa, Yasuhiro Ishimaru, Masato Igura, Masato Kuramata, Tadashi Abe, Takeshi Senoura, Yoshihiro Hase, Tomohito Arao, Naoko K. Nishizawa, and Hiromi Nakanishi, which was first published November 6, 2012; 10.1073/pnas.1211132109 (Proc Natl...

Capsules are surface layers of hydrated capsular polysaccharides (CPSs) produced by many bacteria. The human pathogen Salmonella enterica serovar Typhi produces “Vi antigen” CPS, which contributes to virulence. In a conserved strategy used by bacteria with diverse CPS structures, translocation of Vi antigen to the cell surface is driven by...

Host-associated microbiota help defend against bacterial pathogens; however, the mechanisms by which pathogens overcome this defense remain largely unknown. We developed a zebrafish model and used live imaging to directly study how the human pathogen Vibrio cholerae invades the intestine. The gut microbiota of fish monocolonized by symbiotic strain Aeromonas...

Our studies of the SNP rs8060947 determine that the A allele is associated with increased invasion of Salmonella enterica serovar Typhi and increased susceptibility to typhoid fever (1). Gilchrist et al. (2) now provide evidence that the A allele is also associated with increased risk for bacteremia, and the association...

Performing a genome-wide association study of Salmonella enterica serovar Typhi (S. Typhi) invasion, Alvarez et al. (1) identify a trait-associated SNP, rs8060947, in VAC14. rs8060947 is an expression quantitative trait locus for VAC14 RNA expression, and carriage of the A allele is associated with reduced VAC14 RNA and protein expression,...

Salmonella enterica serovar Typhimurium ST313 is a relatively newly emerged sequence type that is causing a devastating epidemic of bloodstream infections across sub-Saharan Africa. Analysis of hundreds of Salmonella genomes has revealed that ST313 is closely related to the ST19 group of S. Typhimurium that cause gastroenteritis across the world....

The facultative human pathogen Vibrio cholerae changes its transcriptional profile upon oral ingestion by the host to facilitate survival and colonization fitness. Here, we used a modified version of recombination-based in vivo expression technology to investigate gene silencing during the in vivo passage, which has been understudied. Using a murine...

In a pet food factory in Reno, NV, researchers from IBM Research and Mars, Inc. are conducting an experiment that may someday revolutionize food safety. For more than two years, they’ve taken regular samples of poultry meal—a protein-rich mash of chicken parts—as it enters the factory on its way to...

Bacterial cells modulate transcription in response to changes in iron availability. The ferric uptake regulator (Fur) senses intracellular iron availability and plays a central role in maintaining iron homeostasis in Bacillus subtilis. Here we utilized FrvA, a high-affinity Fe2+ efflux transporter from Listeria monocytogenes, as an inducible genetic tool to...

Campylobacter jejuni, a leading cause of bacterial gastroenteritis, is naturally competent. Like many competent organisms, C. jejuni restricts the DNA that can be used for transformation to minimize undesirable changes in the chromosome. Although C. jejuni can be transformed by C. jejuni-derived DNA, it is poorly transformed by the same...

Heavy metals from urban runoff preserved in sedimentary deposits record long-term economic and industrial development via the expansion and contraction of a city’s infrastructure. Lead concentrations and isotopic compositions measured in the sediments of the harbor of Ostia—Rome’s first harbor—show that lead pipes used in the water supply networks of...

Genetic variant tied to risk of typhoid fever Salmonella bacteria. Image courtesy of Flickr/National Institute of Allergy and Infectious Diseases. Worldwide, Salmonella enterica serovar Typhi (S. Typhi) causes around 20 million typhoid infections every year, and 1–5% of infected individuals chronically carry the pathogen, notable among which is the storied...

The enteroinvasive bacterium Shigella is a facultative intracellular bacterium known, in vitro, to invade a large diversity of cells through the delivery of virulence effectors into the cell cytoplasm via a type III secretion system (T3SS). Here, we provide evidence that the injection of T3SS effectors does not necessarily result...

Picornaviruses use internal ribosome entry sites (IRESs) to translate their genomes into protein. A typical feature of these IRESs is their ability to bind directly to the eukaryotic initiation factor (eIF) 4G component of the eIF4F cap-binding complex. Remarkably, the hepatitis A virus (HAV) IRES requires eIF4E for its translation,...

Cyclic di-3′,5′-adenosine monophosphate (c-di-AMP) is a broadly conserved bacterial second messenger that has been implicated in a wide range of cellular processes. Our earlier studies showed that c-di-AMP regulates central metabolism in Listeria monocytogenes by inhibiting its pyruvate carboxylase (LmPC), a biotin-dependent enzyme with biotin carboxylase (BC) and carboxyltransferase (CT)...

Trained in both human medical and veterinary sciences, Xiang-Jin Meng has made numerous contributions to the field of comparative viral pathogenesis. His achievements concerning emerging, reemerging, and zoonotic viral diseases include the discovery of swine and avian hepatitis E viruses (HEV) and the invention of a commercial vaccine against porcine...

Botulism is characterized by flaccid paralysis, which can be caused by intoxication with any of the seven known serotypes of botulinum neurotoxin (BoNT), all of which disrupt synaptic transmission by endoproteolytic cleavage of SNARE proteins. BoNT serotype A (BoNT/A) has the most prolonged or persistent effects, which can last several...

The Picornaviridae are a diverse family of RNA viruses including many pathogens of medical and veterinary importance. Classically considered “nonenveloped,” recent studies show that some picornaviruses, notably hepatitis A virus (HAV; genus Hepatovirus) and some members of the Enterovirus genus, are released from cells nonlytically in membranous vesicles. To better...

Listeria monocytogenes is a common food-borne pathogen that can disseminate from the intestine and infect multiple organs. Here, we used sequence tag-based analysis of microbial populations (STAMP) to investigate L. monocytogenes population dynamics during infection. We created a genetically barcoded library of murinized L. monocytogenes and then used deep sequencing...

XIAP-associated factor 1 (XAF1) is a tumor suppressor that is commonly inactivated in multiple human neoplasms. However, the molecular mechanism underlying its proapoptotic function remains largely undefined. Here, we report that XAF1 induction by heavy metals triggers an apoptotic switch of stress response by destabilizing metallothionein 2A (MT2A). XAF1 directly...

Global distribution of hepatocellular carcinomas (HCCs) is dominated by its incidence in developing countries, accounting for >700,000 estimated deaths per year, with dietary exposures to aflatoxin (AFB1) and subsequent DNA adduct formation being a significant driver. Genetic variants that increase individual susceptibility to AFB1-induced HCCs are poorly understood. Herein, it...