2006 National Escherichia, Shigella, Vibrio Reference Unit at CDC Under a magnification of 6836x, this colorized scanning electron micrograph (SEM) depicted a number of Gram-negative Escherichia coli bacteria of the strain O157:H7, which is one of hundreds of strains of this bacterium. Although most strains are harmless, and live in the intestines of healthy humans and animals, this strain produces a powerful toxin, which can cause severe illness.E. coli O157:H7 was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea; the outbreak was traced to contaminated hamburgers. Since then, most infections have come from eating undercooked ground beef.The combination of letters and numbers in the name of the bacterium refers to the specific markers found on its surface, which distinguishes it from other types of E. coli. See PHIL 8800 for a black and white version of this image. Escherichia coli O157:H7 is an emerging cause of foodborne illnes.

You probably know that your DNA contains the blueprints for every protein your body needs, plus instructions on how to regulate them. But your DNA could also strongly influence your immune system, making you more or less susceptible to bacterial infections, according to a new study led by researchers from Duke University. The study was published this week in the Journal of Infectious Diseases.

Scientists have already had some inklings of the relationship between genes and infectious diseases—for example, people with the genetic mutation for cystic fibrosis don’t usually get typhoid, which is caused by bacteria. Bacteria and viruses, in turn, can also affect your genes.

For this study, the researchers wanted to see if genes affected a person’s likelihood of contracting a common bacterial infection. The researchers infected 30 participants with E. coli bacteria, a common cause of diarrhea. For the next eight days, the researchers watched for symptoms—six participants basically showed no symptoms, while another six were debilitated by the infection—and then drew their blood.

The researchers were checking the blood for gene expression. While every cell might have thousands of genes, only a select few are activated at any given time, turned on throughout the process of development or by external factors like smoking and diet.

Bacteria, it seems, can also modify gene expression—when the researchers compared the gene expression of participants with severe symptoms and those with few symptoms, they found significant differences in the expression of 29 genes related to immune function. It seems that certain genes were turned on when the bacteria were present, making the participants more immune. They anticipate that those variations could help predict which patients will react strongly to an E. coli infection.

What’s not clear, though, is if the participants with few symptoms had mutations in those particular genes, or if those genes reacted more strongly to the presence of the bacteria. To answer that question and to further confirm their findings, the researchers hope to perform similar experiments with other types of bacteria and viruses, paying special attention to those 29 genes they suspect play a role in disease resistance. If they’re right, it’s possible that someday, treatments for infectious diseases might rely more on epigenetics, activating infection-resistant genes so that patients suffer less.