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The finding came as a surprise to Kirienko's team, which first noticed the effect in experiments designed to investigate the mechanisms of pathogenesis or Pseudomonas aeruginosa ( P. aeruginosa ), a potentially deadly disease that affects some 51,000 US hospital patients each year, according to the Centers for Disease Control.
Her lab, like thousands of others worldwide, uses C. elegans as a model organism to study the effects of disease, drugs, toxins, and other processes that affect humans and animals. In many C. elegans research labs worms eat Escherichia coli ( E. coli ), a common human gut bacteria that is itself a model organism
"We found that switching between E. coli strain OP50 and strain HT115 dramatically altered the worm's stress tolerance, "Kirienko says. She says it took about two years of follow-up studies to isolate the biochemical mechanism of stress and pathogen resistance.
"The key difference between the two diets is the ability of HT115 and OP50 to acquire B12 from the environment," says lead coauthor Alexey Revtovich, a research scientist. “We showed that HT115 is far more efficient at this, making about eight times as much of the protein that it needs to harvest B12 than compared to OP50.”
The researchers did numerous tests to confirm their results and rule out other possible mechanisms for the effect. They also found that C. elegans on an HT115 diet resisted infection from another deadly human pathogen, Enterococcus faecalis
C. elegans labs worldwide to pay attention to possible differential impacts of diet on experimental outcomes, says coauthor and undergraduate Ryan Lee
"Some labs use OP50 as their standard food, and others use HT115 or another strain of E. coli "Lee says. "Our results show there are significant metabolic differences between these diets, and most likely these differences could contribute to substantial uncertainty in research outcomes."
The National Institutes of Health, the Cancer Prevention and Research Institute of Texas (CPRIT), and the Welch Foundation funded the work
Source: Rice University