Heat and Pressure Resistance in Escherichia coli Relates to Protein Folding and Aggregation

Abstract

The locus of heat resistance (LHR) confers extreme heat resistance in Escherichia coli. This study explored the role of the LHR in heat and pressure resistance of E. coli, as well as its relationship with protein folding and aggregation in vivo. The role of LHR was investigated in E. coli MG1655 and the pressure resistant E. coli LMM1010 expressing an ibpA-yfp fusion protein to visualize inclusion bodies by fluorescence microscopy. The expression of proteins by the LHR was determined by proteomic analysis; inclusion bodies of untreated and treated cells were also analyzed by proteomics, and by fluorescent microscopy. In total, 11 proteins of LHR were expressed: sHSP20, ClpK GI , sHSP, YdfX1 and YdfX2, HdeD, KefB, Trx, PsiE, DegP, and a hypothetical protein. The proteomic analysis of inclusion bodies revealed a differential abundance of proteins related to oxidative stress in strains carrying the LHR. The LHR reduced the presence of inclusion bodies after heat or pressure treatment, indicating that proteins expressed by the LHR prevent protein aggregation, or disaggregate proteins. This phenotype of the LHR was also conferred by expression of a fragment containing only sHSP20, ClpK GI , and sHSP. The LHR and the fragment encoding only sHSP20, ClpK GI , and sHSP also enhanced pressure resistance in E. coli MG1655 but had no effect on pressure resistance of E. coli LMM1010. In conclusion, the LHR confers pressure resistance to some strains of E. coli, and reduces protein aggregation. Pressure and heat resistance are also dependent on additional LHR-encoded functions.

A recently isolated human commensal Escherichia coli ST10 clone member mediates enhanced thermotolerance and tetrathionate respiration on a P1 phage‐derived IncY plasmid

“…S. enterica probably readily survived in dried egg powder that was a frequent source of outbreaks of salmonellosis in the 1940s. In this line, the TLPQC locus has recently also been shown to mediate pressure tolerance and tolerance against oxidizing agents used in the food industry (Li et al, 2020;Wang et al, 2020).…”

“…The contribution of plasmids toward genomic plasticity reaches beyond the provision of pathogenicity factors, antimicrobial resistance determinants, and degradation pathways (Koraimann, 2018;Pilla and Tang, 2018;Shintani et al, 2010). One plasmid-encoded feature is the up to 19 kbp long Transmissible Locus of Protein Quality Control (TLPQC) which mediates elevated tolerance against lethal temperature, pressure, and oxidatives (Boll et al, 2017;Lee et al, 2016;Li and Ganzle, 2016;Li et al, 2020;Wang et al, 2020). The TLPQC locus, originally derived from an environmental species, has also been obtained by clinically relevant bacteria (Bojer et al, 2012).…”

Control of pathogenic and spoilage bacteria in meat and meat products by high pressure: Challenges and future perspectives

“…It has been shown that genetic strategies supporting the acquisition of pressure resistance include both loss and acquisition of some genes (Garcia-Hernandez, 2015; Hauben et al, 1997;Li et al, 2020;Vanlint et al, 2013). Resistance of pathogens to high pressure was described in wild-type strains or to laboratory-based selection and genetic modifications.…”

“…However, the relationship between high pressure and protein aggregation is not very clear. Some studies showed that high pressure caused formation of cytosolic‐aggregated clumps corresponding to aggregation of cytoplasmic proteins and condensation of the nucleoid in both Gram‐positive and Gram‐negative bacteria (Kaletunc, Lee, Alpas, & Bozoglu, 2004; Mañas & Mackey, 2004; Mohamed, Diono, & Yousef, 2012), while other studies, which were based on microscopic observations with single cells that were labeled with fluorescent indicators of protein aggregation, demonstrated that high pressure dissociates intracellular protein aggregates (Govers & Aertsen, 2015; Govers, Dutre, & Aertsen, 2014; Li et al., 2020). High pressure induces intracellular oxidative stress through the increased oxidation of cytoplasmic disulfide bonds and the accumulation of the catalyst iron, which is induced by denaturation of proteins containing Fe‐S clusters in the cytoplasm (Aertsen et al., 2005; Gänzle & Liu, 2015).…”

“…The acquisition of a transmissible genomic island locus of heat resistance (LHR) has been found to confer cross‐protections to stresses such as pressure, heat, and chlorine; it is present in approximately 2% of strains of E. coli , including pathogenic strains, and occurs in diverse pathogenic species of β‐ and γ‐Proteobacteria including P. aeruginosa , Cronobacter sakazakii , and Klebsiella pneumoniae (Li et al., 2020; Mercer et al., 2015; Mercer, Walker, Yang, McMullen, & Gänzle, 2017; Zhi et al., 2016). Three proteins encoded by the LHR including heat shock proteins sHsp20 and sHsp, and disaggregase ClpKGI (ATP‐dependent HSP100 family protein), reduce protein aggregation and increase pressure resistance of E. coli , indicating that the increased resistance induced by the LHR may be related to the protein folding and aggregation (Li et al., 2020). Other studies also demonstrated that heat shock proteins can aggregate cytoplasmic proteins: sHSP20 and ClpK GI can bind to misfolded proteins and prevent aggregation, or disaggregate and refold the denatured proteins (Hunke & Betton, 2003; Lee et al., 2015, 2018; Lee, Wigren, Lünsdorf, & Römling, 2016).…”