# Transcription of _Listeria monocytogenes_ Key Virulence Genes on Tomato, Cucumber and Carrot
## 4 Discussion  
The pathogenic potential of _L monocytogenes_, assessed almost exclusively by invasion to cell lines, such as Caco-2, THP-1 and HT-29, is affected by abiotic and biotic stimuli that include exposure to temperature, acid and osmotic fluctuations as well as the food \begin{table}
\begin{tabular}{c c c c c c c c c} \hline  & & _prfA_ & _sigB_ & _plcA_ & _plcB_ & _hly_ & _inIA_ & _inlB_ & _inlC_ & _inlJ_ \\ \hline _prfA_ & r & & & & & & & & \\ \hline \multicolumn{2}{c}{_p_} & & & & & & & & \\ \hline \multicolumn{2}{c}{_sigB_} & r & **0.2548** & & & & & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0193 & & & & & & & \\ \hline \multicolumn{2}{c}{_plcA_} & r & **0.4970** & **0.3361** & & & & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0000 & 0.0018 & & & & & & \\ \hline \multicolumn{2}{c}{_plcB_} & r & **0.4347** & **0.2836** & 0.1373 & & & & \\ \hline \multicolumn{2}{c}{_plcB_} & 0.0000 & 0.0089 & 0.2128 & & & & & \\ \hline \multicolumn{2}{c}{_hly_} & r & **0.4430** & 0.0654 & 0.2050 & \(-\)0.0811 & & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0000 & 0.5545 & 0.0614 & 0.4631 & & & & \\ \hline \multicolumn{2}{c}{_inlA_} & r & **0.7528** & **0.2293** & **0.3497** & **0.6363** & 0.1316 & & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0000 & 0.0359 & 0.0011 & 0.0000 & 0.2327 & & & \\ \hline \multicolumn{2}{c}{_inlB_} & r & **0.7959** & **0.2581** & **0.4265** & **0.3001** & **0.4618** & **0.7264** & & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0000 & 0.0178 & 0.0001 & 0.0056 & 0.0000 & 0.0000 & & & \\ \hline \multicolumn{2}{c}{_inlC_} & r & **0.7218** & **0.2803** & **0.4250** & 0.1368 & **0.5274** & **0.5850** & **0.8322** & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0000 & 0.0098 & 0.0001 & 0.2147 & 0.0000 & 0.0000 & 0.0000 & & & \\ \hline \multicolumn{2}{c}{_inlJ_} & r & **0.4045** & **0.4817** & **0.3182** & 0.1934 & **0.3311** & **0.3646** & **0.5134** & **0.6898** & & \\ \hline \multicolumn{2}{c}{_p_} & 0.0001 & 0.0000 & 0.0032 & 0.0780 & 0.0021 & 0.0006 & 0.0000 & 0.0000 & 0.0000 & \\ \hline \multicolumn{2}{c}{Statistically significant correlations (_p_ \(<\) 0.05) are presented in bold.} & & & & & & & \\ \end{tabular}
\end{table} 
Table 3: Pearson product moment (r) correlations between the relative transcription of each pair of genes. matrix and co-existing microorganisms [18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32]. Correlation between the transcriptomic response of the pathogen to the above stresses with invasiveness, in some cases was successful [13; 21]. Several studies have assessed the transcription of virulence associated genes during growth of _L. monocytogenes_ on a food matrix at various storage temperatures and times [8; 9; 10; 11; 12; 13; 15; 16; 17]. The basic conclusions of these studies were that their transcription was, in the majority of the cases, affected by the experimental conditions (time, temperature, food matrix) and this effect was strain dependent. Indeed, when more than one strain was included in a study, substantial differences in gene transcription were reported [8; 10; 11; 12; 13; 15]. In the present study, only _L. monocytogenes_ strain LQC 15257 was employed. The relative transcription of virulence associated genes of this strain was also assessed on the surface of rocket and melon [16], on the surface of BHI agar under the effect of lemongrass essential oil [47], in co-culture with _Aspergillus flavus_ strain 18.4 [48] as well as after in vitro exposure to human gastric and duodenal aspirates [45]. Thus, a database of responses to various stimuli has been established, which is enriched with the transcriptomic responses assessed in the present study. _sigB_ and _prfA_ possess very important role in homeostasis and virulence capacity of the pathogen [1]. Moreover, transcription of _prfA_ may be initiated by three promoter sites, one of which is partially \(\sigma^{\text{B}}\)-dependent [48]. In the present study, only weak association of the relative transcription between _sigB_ and _prfA_ was revealed.