Investigating the role of the Listeria monocytogenes noncoding RNA Rli47 during the response to environmental stressors.

Listeria monocytogenes is a food-borne pathogen that can cause severe disease in immunocompromised persons, and its ability to survive stressors encountered in food production environments (FPEs) makes it difficult to eliminate from the food chain. Previous transcriptomic analysis revealed that in response to lactic acid exposure, L. monocytogenes significantly upregulates Rli47, a noncoding RNA that has previously been shown to interact with the ilvA transcript and suppress growth of L. monocytogenes in the absence of isoleucine. We show that at logarithmic phase, an rli47 deletion mutant had a higher survival compared to the parent strain after exposure to lactic acid. Flow cytometry indicated that lactic acid exposure did not differentially affect the proportion of metabolically active cells in the deletion mutant and wild type. Transcriptomic analysis and in silico target prediction suggested that Rli47 could affect pathways involved with cell envelope structure; due to the link between cell envelope integrity and organic acid stress, it is possible that in the absence of rli47 the cell envelope of logarithmic phase L. monocytogenes cells is more resistant to lactic acid exposure. These results suggest that Rli47 functionality may vary due to factors including temperature and nutrient availability.