NOV 02, 2015 5:04 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
JAN 15, 2020
Microbiology
JAN 15, 2020
Scientists Engineer a New Kind of Life Form
Usig cells harvested from frogs, researchers created tiny robots....
FEB 14, 2020
Microbiology
FEB 14, 2020
Beneath the Surface, We All Carry the Same Microbes in Our Skin
Our skin is a critical barrier, and it is made up of three layers. It also carries a community of microbes - a skin microbiome....
FEB 05, 2020
Technology
FEB 05, 2020
Portable Device Detects Food-borne illness
 Foodborne illnesses kill 3,000 people on an annual basis. According to the Centers for Disease Control and Prevention, an estimated 48 million people...
MAR 01, 2020
Microbiology
MAR 01, 2020
Preventing and Preparing for COVID-19
Worldwide, the number of COVID-19 cases, caused by the SARS-CoV-2 virus, is still rising....
MAR 27, 2020
Chemistry & Physics
MAR 27, 2020
Hand Sanitizer Shorage: Liquor, Perfume, and Medication Producers Joined the Race to Restock the Shelves
Amid the coronavirus pandemic, the habit of thorough and frequent handwashing are among the best defense against the contagious disease. But when soap and water aren't available, hand sanitiz...
MAR 29, 2020
Earth & The Environment
MAR 29, 2020
Incinerators and landfills breed antibiotic resistant genes
Here’s a compelling reason to start composting: your municipal solid waste is producing airborne antibiotic-resistance genes. Duhn duhn duhhhhn. But...
Loading Comments...