Science and Medicine

Discovery one day may help scientists develop ways to control this common food poisoning cause.

A study led by researchers at UC Davis has found how the bacteria Salmonella enterica—a common cause of food poisoning—exploits immune response in the human gut to enhance its own reproductive and transmission success. The strategy gives Salmonella a growth advantage over the beneficial bacteria that normally are present in the intestinal tract and promotes the severe diarrhea that spreads the bacteria to other people.

The study, “Gut inflammation provides a respiratory electron acceptor for Salmonella,” is published in the Sept. 23 issue of the journal Nature.

“The human body normally has 10 times more microbes than human cells that help protect us against infection from disease-causing bacteria,” said Andreas Bäumler, professor of medical microbiology and immunology at the UC Davis School of Medicine and the principal investigator of the study. “We have discovered Salmonella’s cunning trick that allows it to quickly take over and outgrow the beneficial microbes in our intestine.”

All bacteria must generate energy in order to live and reproduce, either by respiration—which usually requires oxygen—or fermentation. Because essentially no oxygen is available in our intestines, the beneficial bacteria that reside there tend to use fermentation, which is less efficient than respiration for obtaining energy.

Read more: Investigators Find that Salmonella Creates Environment for Growth

“The bigger the tooth, the bigger area for chips to develop and, therefore, the more force the animal can produce.”

Were our early mammalian ancestors vegetarians, vegans, or omnivores. It’s difficult for anthropologists to determine the diet of early mammalians because current fossil analysis provides too little information. But a new method that measures the size of chips in tooth fossils can help determine the kinds of foods these early humans consumed.

Professor Herzl Chai of Tel Aviv University’s School of Mechanical Engineering, in collaboration with scientists from George Washington University and the U.S. National Institute of Standards and Technology (NIST), has developed an equation for determining how the size of a chip found in the enamel of a tooth relates to the bite force needed to produce the chip. With the aid of this information, researchers can better determine the type of food that animals, and early humans, could have consumed during their lifetimes.

Teeth are the only relevant fossils with staying power, Prof. Chai said. Made of hard, mineralized material, teeth from animals that are thousands of years old remain relatively intact. Teeth that display a greater number of large chips indicate that animals like our early ancestors were consuming harder foods such as nuts, seeds or items with bones. A lesser amount of small chips demonstrates that the animal’s diet more likely consisted of softer foods, such as vegetation. Prof. Chai’s findings were recently reported in the journal Biology Letters.

Read more: Scientists Develop Method for Determining Diet of our Early Ancestors