The heat-shock response of Listeria monocytogenes comprises genes involved in heat shock, cell division, cell wall synthesis, and the SOS response

Abstract

The food-borne pathogen Listeria monocytogenes has the ability to survive extreme environmental conditions due to an extensive interacting network of stress responses. It is able to grow and survive at relatively high temperatures in comparison with other non-sporulating food-borne pathogens. To investigate the heat-shock response of L. monocytogenes, whole-genome expression profiles of cells that were grown at 37 6C and exposed to 48 6C were examined using DNA microarrays. Transcription levels were measured over a 40 min period after exposure of the culture to 48 6C and compared with those of unexposed cultures at 37 6C. After 3 min, 25 % of all genes were differentially expressed, while after 40 min only 2 % of all genes showed differential expression, indicative of the transient nature of the heat-shock response. The global transcriptional response was validated by analysing the expression of a set of 13 genes by quantitative PCR. Genes previously identified as part of the class I and class III heat-shock response and the class II stress response showed induction at one or more of the time points investigated. This is believed to be the first study to report that several heat-shock-induced genes are part of the SOS response in L. monocytogenes. Furthermore, numerous differentially expressed genes that have roles in the cell division machinery or cell wall synthesis were down-regulated. This expression pattern is in line with the observation that heat shock results in cell elongation and prevention of cell division.

The Formation of Streptococcus mutans Persisters Induced by the Quorum-Sensing Peptide Pheromone Is Affected by the LexA Regulator

“…A perfect inverted repeat (IR; 15 bp) was found in the promoter region of SMU.2027 (see Fig. S2 in the supplemental material), suggesting a putative binding site for autoregulatory activity as observed in other LexA-like regulators (39). Bioinformatic analysis of S. mutans SMU.2027 showed that it possesses the two conserved domains found in LexA-like regulators: (i) a helix-turnhelix motif involved in sequence-specific DNA binding and (ii) a signal peptidase-like serine peptidase domain.…”

Development and optimization of an EGFP-based reporter for measuring the general stress response inListeria monocytogenes

“…Together the data presented here demonstrate that the P lmo2230 ::egfp reporter is a useful tool that can be used to investigate the conditions and mechanisms that trigger the activation of s B in L. monocytogenes. Expression of lmo2230 was shown to be rapid and transient both after heat shock at 48°C, with a 10-fold induction observed after 3 min of heat stress 32 and also 15 min after osmotic upshock when more than 160-fold higher levels of lmo2230 in wild-type were reported comparing to unstressed cells at time zero. 31 Taken together these findings give an opportunity for monitoring activation of s B in real time by following lmo2230-promoter-driven expression after a sudden change of environmental conditions.…”

“…The long half-life of EGFP (estimated at greater than 24 h) 42 makes it impossible to observe a drop in s B activity after the removal of stress, while this decrease can be demonstrated by monitoring the transcript levels of lmo2230 and other s B -regulated genes under similar conditions 31 and after heat shock. 32 Future versions of this reporter could include less stable GFP variants (with ssrA RNA tags recognized by housekeeping proteases) 42 in order to overcome this limitation. When the time scale for s B activation was compared between the RNA based approach described earlier 31 and the P lmo2230 ::egfp reporter (Fig.…”

“…To determine whether our reporter system is able to detect quick changes of s B activity reported by earlier studies, 31,32 the relative fluorescence was investigated after osmotic upshock. In contrast to steady-state growth experiments, cells were grown without NaCl supplementation up to OD 600 = 0.6 then osmotically shocked by addition of solid NaCl (0.5 M) and samples were taken at suitable intervals from vigorously shaken cultures for microscopic observation (Fig.…”

Listeria monocytogenes

“…46 The presence of an SOS response in L. monocytogenes was verified and new members of the SOS regulon were identified by comparing the transcription profiles of a wild-type strain and ΔrecA. 47 The promoters of two previously-described 48 SOS-response genes recA and yneA (the cell division inhibitor) were fused into a vector containing a promoterless copy of the egfp gene to verify the activation of SOS after exposure to DNA-damaging agent mitomicin C (MMC). Both recA and yneA were found to be strongly activated one hour after exposure to MMC, as indicated by a strong increase in cellular fluorescence that was visualized microscopically (Fig.…”