Thelmo1078gene encoding a putative UDP-glucose pyrophosphorylase is involved in growth ofListeria monocytogenesat low temperature

Abstract

The gram-positive bacterium Listeria monocytogenes is a food-borne pathogen with the ability to grow at low temperature. Given the importance of refrigeration as a means of food preservation, the psychrotolerant nature of this microorganism poses a significant public health hazard. In order to better understand the mechanisms underlying cold adaptation of L. monocytogenes, a library of Tn917-lac insertional mutants was screened. A cold-sensitive mutant, named cs1, was isolated and found to be also sensitive to salt-stress. Analysis of the transposon insertion site allowed the identification of a gene, lmo1078, encoding a putative UDP-glucose pyrophosphorylase with 68% identity to GtaB from Bacillus subtilis. In gram-positive bacteria, this enzyme catalyses the formation of UDP-glucose, a precursor of membrane glycolipids and cell envelope teichoic acids. Complementation of mutant cs1 with a wild-type copy of lmo1078 restored its ability to grow at low temperature and high salt concentration, indicating that UDP-glucose pyrophosphorylase activity is important for cold and salt tolerance. These results are thus consistent with previous studies showing the importance of the cell envelope in L. monocytogenes adaptation to stressful conditions.