RESUMEN
The ability of bacteria to resist heat shock allows them to adapt to different environments. In addition, heat shock resistance is known for their virulence. Our previous study showed that the AI-2/luxS quorum sensing system affects the growth characteristics, biofilm formation, and virulence of Glaesserella parasuis. The resistance of quorum sensing system deficient G. parasuis to heat shock was obviously weaker than that of wild type strain. However, the regulatory mechanism of this phenotype remains unclear. To illustrate the regulatory mechanism by which the quorum sensing system provides resistance to heat shock, the transcriptomes of wild type (GPS2), ΔluxS, and luxS complemented (C-luxS) strains were analyzed. Four hundred forty-four differentially expressed genes were identified in quorum sensing system deficient G. parasuis, which participated in multiple regulatory pathways. Furthermore, we found that G. parasuis regulates the expression of rseA, rpoE, rseB, degS, clpP, and htrA genes to resist heat shock via the quorum sensing system. We further confirmed that rseA and rpoE genes exerted an opposite regulatory effect on heat shock resistance. In conclusion, the findings of this study provide a novel insight into how the quorum sensing system affects the transcriptome of G. parasuis and regulates its heat shock resistance property.
RESUMEN
PURPOSE: An attempt was made to investigate N-nitrosomorpholine (NNM) induced carcinogenic processes in rat liver. MATERIALS AND METHODS: Rats were fed with NNM (200 mg/l) for 7 weeks, after then stopped. Length of telomere and activity of telomerase were analyzed. Hepatocytes were isolated and grown on tissue culture. Heat shock was treated at 43oC, and patterns of cell death ere evaluted by fluorescent study. Nuclei and nucleoli were isolated for analysis of various signal molecules. RESULTS: Shortening of telomere length presented in NNM treated liver, but induction of telomerase was not found. Ex vivo hepatocytes from 10~12th week showed increased heat shock resistance at 43oC. NNM-treated hepatocytes exhibited heat shock induced cell death (necrosis) after 7 hours, whereas the control showed necrosis after 3 hours. The signal molecules related to nucleolar growth revealed increased expression which included B23, C23, p38, Erk1/2 and p120. Partial degradation of B23 and Erk2 was noted in necrosis of NNM treated hepatocytes induced by heat shock. CONCLUSION: The hepatocytes at the stage of 10~12th week in the stop experiment of NNM are situated in the tumour promotion. Those cells showed various metabolic alterations. We found that the increased growth related signals were accompanied with increased heat shock resistance, telomere shortening but no induction of telomerase.