In cases of chronic undernutrition, some commensal bacteria , notably lactobacilli, encourage the growth of their host by directly stimulating the expression and activity of digestive enzymes. Researchers at the Institute of Functional Genomics of Lyon (IGFL - CNRS/Université Claude Bernard Lyon 1/ENS de Lyon) studied this phenomenon on the fruit fly, and found that it led to a better assimilation of nutrients and thus a better nutritional efficiency despite a state of undernutrition. Studying the phenomenon further, the scientists demonstrated that upon pathogen infections, this nutritional optimization process was altered, aggravating the state of malnutrition.
These findings, published in Cell Host and Microbe on October 1, 2015, highlight the key role of microbial environments in the physiological response to malnutrition. They could also pave the way to studies on new treatments that would stem from lactobacilli to fight child undernutrition.
 Micro-organisms living in association with a multicellular organism without harming it (such as intestinal flora)