An infectious agent of deception, exposed through proteomics

September 29, 2006

RICHLAND, Wash. -- Salmonella bacteria, infamous for food poisoning that kills hundreds of thousands worldwide, infect by stealth. They slip unnoticed into and multiply inside macrophages, the very immune system cells the body relies on to seek and destroy invading microbes.

Just how Salmonella escapes detection by macrophages, turning predator cells to prey complicit in promoting infection, has seemed impossibly complicated, a needle-in-a-haystack proposition involving thousands of proteins, the building blocks that carry out cells' vital functions.

Applying the high-volume sorting and analytical power of proteomics--a detailed survey of microbial proteins present in the 24 hours that follow mouse-macrophage infection--a team led by Liang Shi of the Department of Energy's Pacific Northwest National Laboratory has turned up a suspect protein.

The discovery of the protein, dubbed STM3117, is detailed today (Sept. 29) in The Journal of Biological Chemistry. Knocking out the gene that codes for STM3117, the researchers subsequently crippled the microbe's ability to multiply inside macrophages. Shi and colleagues say the protein and two closely related proteins discovered in the study are similar in genetic sequence to those known to make and modify chemicals in the microbe's cell wall called peptidoglycan.

Drug and vaccine designers armed with this mouse-model information can target chemicals or immune responses that disrupt peptidoglycan synthesis and other processes linked to Salmonella's colonization of macrophages in humans, said Joshua Adkins, a co-author on Shi's paper and lead author of a related study in Molecular & Cellular Proteomics last month. A quick identification of these proteins, Adkins added, could help physicians assess the virulence of a given strain.

The candidate proteins were winnowed from among 315 possibilities that emerged through a combination of techniques, culminating in measurements by Fourier-transform mass spectrometry, or FT-MS. A suite of FT-MS instruments customized by co-author and PNNL-based Battelle Fellow Richard D. Smith enabled the team to rapidly separate and identify many proteins at once even as macrophages were being infected.

Most of the initial candidates were designated "house-keeping" proteins, or those whose numbers relative to other proteins remained more or less constant during the course of infection. But 39 proteins shot up in number during bacterial colonization of macrophages, and of those, a handful or so--including STM3117--responded specifically to a macrophage protein associated with resistance to microbial infection. A standard assay called Western blot confirmed the abundance increases of that small group of proteins during infection.
-end-
The work was funded by PNNL and the National Institutes of Health's National Institute of Allergy and Infectious Diseases, and much of the work was performed at the PNNL-based W.R. Wiley Environmental Molecular Sciences Laboratory.

PNNL is a DOE Office of Science laboratory that solves complex problems in energy, national security, the environment and life sciences by advancing the understanding of physics, chemistry, biology and computation. PNNL employs 4,200 staff, has a $725 million annual budget, and has been managed by Ohio-based Battelle since the lab's inception in 1965.

DOE/Pacific Northwest National Laboratory

Related Salmonella Articles from Brightsurf:

Sneaky salmonella finds a backdoor into plants
Researchers have discovered that bacteria such as salmonella, E.coli and listeria have a backdoor to take advantage of humans' reliance on leafy greens for a healthy diet.

Re-trafficking proteins to fight Salmonella infections
New study demonstrates how monitoring all cellular proteins over time and space can improve our understanding of host-pathogen interactions.

Researchers find one-two punch may help fight against Salmonella
Researchers found that dephostatin does not kill Salmonella or stop it from growing.

Food scientists slice time off salmonella identification process
Researchers from Cornell University, the Mars Global Food Safety Center in Beijing, and the University of Georgia have developed a method for completing whole-genome sequencing to determine salmonella serotypes in just two hours and the whole identification process within eight hours.

The discovery of ancient Salmonella
Oldest reconstructed bacterial genomes link agriculture and herding with emergence of new disease.

The function of new microRNAs are identified in Salmonella and Shigella infections
The research, published in Nature Microbiology, could help the search for more effective medicine and delves deeper into understanding the role of microRNAs in gene expression.

Salmonella the most common cause of foodborne outbreaks in the European Union
Nearly one in three foodborne outbreaks in the EU in 2018 were caused by Salmonella.

The nature of salmonella is changing -- and it's meaner
Salmonella is acting up in Michigan, and it could be a model for what's happening in other states, according to a new Michigan State University study.

Salmonella -- how the body fights back
New research shows how our immune system fights back against Salmonella infection.

For salmonella detection, genomic tool emerges as a key
The world's food supply will become safer as the food industry shifts to high-resolution, whole-genome sequencing -- which examines the full DNA of a given organism all at once.

Read More: Salmonella News and Salmonella Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.