NOV 02, 2015 05:04 PM PST

Deciphering Salmonella Host Specificity

WRITTEN BY: Kerry Evans
What makes a strain of Salmonella infect cows, but not humans or birds?

Researchers at the University of Pennsylvania combed the genomes of 580 Salmonella strains for mutations that could determine host specificity.  The group used a technique called “genome-wide association studies” (GWASs) to identify the mutations. GWASs analyze genome sequences to identify mutations associated with specific traits (like diseases).  Often, these analyses focus on SNPs - single nucleotide polymorphisms.  SNPs are genetic mutations that change one DNA base to another - an adenine into a thymine, for example.  Many SNPs are harmless, but some result in amino acid changes.
 
Salmonella displays host specificity.

Salmonella enterica serovar Typhimurium contained a large number of SNPs within genes for surface and secreted proteins.  This particular serovar (or strain) is a common cause of food poisoning in humans. Humans contract this strain of Salmonella by eating contaminated food.  Since Salmonella is a facultative intracellular pathogen, it is able to infect cells that line the intestine, leading to symptoms of food poisoning (diarrhea, nausea, vomiting).  Salmonella prefers to live in association with its host, but is able to survive in the environment - on produce, for example - for weeks.   

According to study author Dieter Schifferli, “we saw this huge variation in proteins on the surface of bacteria or in secretions, which are really the first lines of interaction with the host … if there was so much variation, it suggests it must be linked to something important”.  

Based on their findings, the group focused their attention on the gene for the proteinaceous surface adhesin FimH.  They introduced cow and human-specific fimH mutations into E. coli and tested the bacteria’s ability to adhere to host cells.  They found that a single amino acid change in human-specific FimH caused E. coli to preferentially bind to cow cells.  In other words, this relatively small mutation was responsible for a change in host specificity.  

Schifferli now plans to determine whether there are genetic differences that determine whether Salmonella will cause mild food poisoning or more serious disease.  

Sources: Eurekalert, Salmonella.org, Wikipedia
 
About the Author
  • Kerry received a doctorate in microbiology from the University of Arkansas for Medical Sciences.
You May Also Like
JUL 19, 2018
Cardiology
JUL 19, 2018
HIV Infection Doubles Risk of Heart Disease
Recent study of 150 countries and over 800,000 people shows HIV patients are more than twice as likely to develop Heart Disease than uninfected individuals....
AUG 05, 2018
Microbiology
AUG 05, 2018
The War Beneath Our Feet
The bacteria living in the soils of Earth seem locked in battle with the fungi there....
AUG 14, 2018
Microbiology
AUG 14, 2018
How Ebola Gets Into Cells
Researchers have learned how Ebola gains entry to cells, which can help us stop it....
OCT 01, 2018
Cell & Molecular Biology
OCT 01, 2018
Revealing How Antibiotics Work Against Bacteria
In a first, researchers have directly observed an antibiotic in action as it disrupted the membrane of a bacterial cell....
OCT 11, 2018
Cell & Molecular Biology
OCT 11, 2018
Revealing a 'Double Agent' in the Immune System
Researchers want to enhance our natural defenses to fight a variety of health problems more effectively....
OCT 12, 2018
Videos
OCT 12, 2018
Don't Mess With Microbes
Researchers demonstrate why antibiotics should not be used casually....
Loading Comments...