The alarmone (p)ppGpp is part of the heat shock response ofBacillus subtilis

Abstract

27 Here, B. subtilis was used as a model organism to investigate how cells respond and adapt to 28 proteotoxic stress conditions. Our experiments suggested that the stringent response, caused 29 by raised levels of the (p)ppGpp alarmone, plays a role during thermotolerance development 30 and the heat shock response. Accordingly, our experiments revealed a rapid increase of 31 cellular (p)ppGpp levels upon heat shock as well as salt-and oxidative stress. Strains lacking 32 (p)ppGpp exhibited increased stress sensitivity, while raised (p)ppGpp levels conferred 33 increased stress tolerance to heat-and oxidative stress. During thermotolerance development, 34 stress response genes were highly up-regulated together with a concurrent transcriptional 35 down-regulation of the rRNA, which was influenced by the second messenger (p)ppGpp and 36 the transcription factor Spx. Remarkably, we observed that (p)ppGpp appeared to control the 37 cellular translational capacity and that during heat stress the raised cellular levels of the 38 alarmone were able to curb the rate of protein synthesis. Furthermore, (p)ppGpp controls the 39 heat-induced expression of Hpf and thus the formation of translationally inactive 100S 40 disomes. These results indicate that B. subtilis cells respond to heat-mediated protein 41 unfolding and aggregation, not only by raising the cellular repair capacity, but also by 42 decreasing translation involving (p)ppGpp mediated stringent response to concurrently reduce 43 the protein load for the cellular protein quality control system. 44Author Summary 45 Here we demonstrate that the bacterial stringent response, which is known to slow down 46 translation upon sensing nutrient starvation, is also intricately involved in the stress response 47 of B. subtilis cells. The second messengers (p)ppGpp act as pleiotropic regulators during the 48 adaptation to heat stress. (p)ppGpp slows down translation and is also involved in the 49 transcriptional down-regulation of the translation machinery, together with the transcriptional 3 50 stress regulator Spx. The stress-induced elevation of cellular (p)ppGpp levels confers 51 increased stress tolerance and facilitates an improved protein homeostasis by reducing the 52 load on the protein quality control system. 53Introduction 54 Bacteria have evolved complex and diverse regulatory networks to sense and respond to 55 changes in the environment, which can include physical stresses or nutrient limitations [1].56 The protein quality control system (PQS) comprises a conserved set of chaperones and 57 proteases that monitor and maintain protein homeostasis is present in all cells. Various 58 physical stresses, such as heat stress, favor the unfolding and aggregation of cellular proteins, 59 which can be sensed by heat shock response systems, allowing an appropriate cellular stress 60 response. This response includes the induction of the expression of chaperones and proteases 61 of the PQS, also known as heat shock proteins [2,3]. 62Interestingly, in all cells including B. ...

InMycobacterium abscessus, the stringent factor Rel regulates metabolism, but is not the only (p)ppGpp synthase

“…Our transcriptomics analysis corroborate these results, as they indicate that RelMab does not upregulate stress response genes, but does alter transcription of growth metabolism 10 genes (Table S2, Supplemental file 1). It remains possible that increases in (p)ppGpp stimulate transcription of stress response genes in Mab, as is seen in other species (3,52,74,75) our experiments did not test this because ∆relMab synthesizes similar amounts of (p)ppGpp as wild-type. Our transcriptional data show that RelMab is involved in downregulating metabolism for growth arrest (Fig.…”

“…Stringent inhibition of growth (44)(45)(46)(47)(48)(49)(50) indirectly protects against some stresses and antibiotics that interfere with growth factors. In many species, the stringent response upregulates stress response genes such as heat shock proteins, hibernation factors, and stress-specific transcription factors (3,51,52) and promotes survival in stress (13). The stringent response also helps many bacteria survive through antibiotic treatment by promoting antibiotic tolerance (12).…”