Genome-wide screen for Listeria monocytogenes genes important for growth at high temperatures

Listeria monocytogenes is a Gram-positive food-borne pathogen that is able to grow over a wide temperature range. Although the class I and class III heat-shock genes are known to play an important role in heat shock, information on genes that are essential for growth at high temperatures is scarce. To determine which genes are important for growth at high temperatures (42.5-43 degrees C), we performed a random insertion screening in L. monocytogenes, rendering 28 temperature-sensitive mutants. These mutants showed insertions in genes that play a role in transcription regulation, cell-wall biosynthesis, cell division, translation, transport, sensing, and specific stress responses like the SOS response and the class III heat-shock response. Some of these mutants showed altered morphological characteristics such as cell elongation, reduced cell length, or sickle shapes. Furthermore, the majority of the mutants showed increased heat inactivation after exposure to 55 degrees C compared with the wild-type strain. The role of the specific genes in relation to growth at high temperatures is discussed.