Defining heat shock response for the thermoacidophilic model crenarchaeon Sulfolobus acidocaldarius
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ORIGINAL PAPER
Defining heat shock response for the thermoacidophilic model crenarchaeon Sulfolobus acidocaldarius Rani Baes1 · Liesbeth Lemmens1 · Kim Mignon1,3 · Matthias Carlier2 · Eveline Peeters1 Received: 20 February 2020 / Accepted: 8 June 2020 © Springer Japan KK, part of Springer Nature 2020
Abstract The crenarchaeon Sulfolobus acidocaldarius, growing optimally at temperatures between 75 and 80 °C, thrives in volcanic hot spring habitats that are typified by large temperature gradients, which impose frequent temperature stresses on the cells. Heat shock response is characterized by an upregulation of heat shock proteins, but similar to most (hyper-)thermophilic archaea, S. acidocaldarius seems to be able to bear supra-optimal temperatures with a restricted repertoire of chaperones. Here, we study the physiological consequences of continuous high-temperature stress and rapid heat shock for S. acidocaldarius. Growth experiments and cell viability assays demonstrate that temperatures of 85 °C and higher result in a decreased growth rate and, when the cells are rapidly subjected to a heat shock, a dynamic increase in mRNA levels of all relevant heat shock proteins and a subset of transcription regulators is observed. When exponentially growing cultures are exposed to a heat shock, the survival tipping point is situated around 90 °C, and the rate of heating determines whether cells are able to cope with this stress or whether the defense mechanism immediately fails, leading to extensive cell death. In conclusion, S. acidocaldarius does not seem to be better equipped to handle sudden supra-optimal temperature stress than mesophilic organisms. Keywords Archaea · Sulfolobus · Heat shock · Transcriptional regulation · Thermosome Abbreviations BR Biological replicate HS Heat shock HSP Heat shock protein Pfdα Prefoldin subunit α Pfdβ Prefoldin subunit β sHSP Small heat shock protein Communicated by M. Moracci. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00792-020-01184-y) contains supplementary material, which is available to authorized users. * Eveline Peeters [email protected] 1
Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
2
Department of Electronics and Informatics, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
3
Present Address: Department of Animal Sciences and Aquatic Ecology, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium
td Doubling time TF Transcription factor Thα Thermosome subunit α Thβ Thermosome subunit β Thγ Thermosome subunit γ µ Specific growth rate
Introduction For all living organisms, high-temperature stress compromises cellular and molecular integrity. Therefore, an adequate response to a sudden, rapid temperature rise above the optimal physiological temperature is crucial for the survival and fitness of a species. This so-called heat-shock (HS) response is characterized by an
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