PMID:21378058

Citation	Selby, K, Lindström, M, Somervuo, P, Heap, JT, Minton, NP and Korkeala, H (2011) Important role of class I heat shock genes hrcA and dnaK in the heat shock response and the response to pH and NaCl stress of group I Clostridium botulinum strain ATCC 3502. Appl. Environ. Microbiol. 77:2823-30
Abstract	Class I heat shock genes (HSGs) code for molecular chaperones which play a major role in the bacterial response to sudden increases of environmental temperature by assisting protein folding. Quantitative reverse transcriptase real-time PCR gene expression analysis of the food-borne pathogen Clostridium botulinum grown at 37°C showed that the class I HSGs grpE, dnaK, dnaJ, groEL, and groES and their repressor, hrcA, were expressed at constant levels in the exponential and transitional growth phases, whereas strong downregulation of all six genes was observed during stationary phase. After heat shock from 37 to 45°C, all HSGs were transiently upregulated. A mutant with insertionally inactivated hrcA expressed higher levels of class I HSGs during exponential growth than the wild type, followed by upregulation of only groES and groES after heat shock. Inactivation of hrcA or of dnaK encoding a major chaperone resulted in lower maximum growth temperatures than for the wild type and reduced growth rates under optimal conditions compared to the wild type. The dnaK mutant showed growth inhibition under all tested temperature, pH, and NaCl stress conditions. In contrast, the growth of an hrcA mutant was unaffected by mild temperature or acid stress compared to the wild-type strain, indicating that induced class I HSGs support growth under moderately nonoptimal conditions. We show that the expression of class I HSGs plays a major role for survival and growth of C. botulinum under the stressful environmental conditions that may be encountered during food processing or growth in food products, in the mammalian intestine, or in wounds.
Links	PubMed PMC3126429 Online version:10.1128/AEM.02633-10
Keywords	Bacterial Load; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Biomass; Clostridium botulinum/drug effects; Clostridium botulinum/genetics; Clostridium botulinum/physiology; Clostridium botulinum/radiation effects; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Heat-Shock Response; Hydrogen-Ion Concentration; Microbial Viability/drug effects; Microbial Viability/radiation effects; Molecular Chaperones/genetics; Molecular Chaperones/metabolism; Mutagenesis, Insertional; Osmotic Pressure; Reverse Transcriptase Polymerase Chain Reaction; Spectrophotometry
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
CLOBH:DNAK		GO:0006950: response to stress	ECO:0000315:		P		Figure 6 and Table 3. Both show that the dnaK mutants had a maximum growth rate lower than the wild type strain at various stresses (temperature, pH, etc.)	complete CACAO 3853
CLOBH:DNAK		GO:0071475: cellular hyperosmotic salinity response	ECO:0000315:		P		As seen in figure 6 and table 3, there was a large reduction in growth in the DnaK mutant strain of Clostridium botulinum as compared to the wild type strain of Clostridium botulinum when grown in both 3% and 3.5% NaCl concentrations.	complete CACAO 4147
CLOBH:DNAK		GO:0071468: cellular response to acidity	ECO:0000315:		P		As seen in table 3 and in figure 6, there was a reduction in growth in the DnaK mutant strain of Clostridium botulinum as compared to the wild type strain of Clostridium botulinum when put under the stress of being grown at a pH of 5 or 6.	complete CACAO 4148
CLOBH:DNAK		GO:0034605: cellular response to heat	ECO:0000315:		P		As seen in figure 6 and table 3, there was a large reduction in growth in the DnaK mutant strain of Clostridium botulinum as compared to the wild type strain of Clostridium botulinum when put under the stress of being grown at high temperatures (temperatures greater than 37°C). Also, as seen in figure 7, the DnaK mutant strain of Clostridium botulinum showed much less growth when put under a temperature gradient of 42 to 48°C when grown on TPGY plates.	complete CACAO 4149
CLOBH:DNAK	involved_in	GO:0034605: cellular response to heat	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
CLOBH:DNAK	involved_in	GO:0071468: cellular response to acidic pH	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
CLOBH:DNAK	involved_in	GO:0071475: cellular hyperosmotic salinity response	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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