1
|
Baruzzo G, Serafini A, Finotello F, Sanavia T, Cioetto-Mazzabò L, Boldrin F, Lavezzo E, Barzon L, Toppo S, Provvedi R, Manganelli R, Di Camillo B. Role of the Extracytoplasmic Function Sigma Factor SigE in the Stringent Response of Mycobacterium tuberculosis. Microbiol Spectr 2023; 11:e0294422. [PMID: 36946740 PMCID: PMC10100808 DOI: 10.1128/spectrum.02944-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 02/15/2023] [Indexed: 03/23/2023] Open
Abstract
Bacteria respond to nutrient starvation implementing the stringent response, a stress signaling system resulting in metabolic remodeling leading to decreased growth rate and energy requirements. A well-characterized model of stringent response in Mycobacterium tuberculosis is the one induced by growth in low phosphate. The extracytoplasmic function (ECF) sigma factor SigE was previously suggested as having a key role in the activation of stringent response. In this study, we challenge this hypothesis by analyzing the temporal dynamics of the transcriptional response of a sigE mutant and its wild-type parental strain to low phosphate using RNA sequencing. We found that both strains responded to low phosphate with a typical stringent response trait, including the downregulation of genes encoding ribosomal proteins and RNA polymerase. We also observed transcriptional changes that support the occurring of an energetics imbalance, compensated by a reduced activity of the electron transport chain, decreased export of protons, and a remodeling of central metabolism. The most striking difference between the two strains was the induction in the sigE mutant of several stress-related genes, in particular, the genes encoding the ECF sigma factor SigH and the transcriptional regulator WhiB6. Since both proteins respond to redox unbalances, their induction suggests that the sigE mutant is not able to maintain redox homeostasis in response to the energetics imbalance induced by low phosphate. In conclusion, our data suggest that SigE is not directly involved in initiating stringent response but in protecting the cell from stress consequent to the low phosphate exposure and activation of stringent response. IMPORTANCE Mycobacterium tuberculosis can enter a dormant state enabling it to establish latent infections and to become tolerant to antibacterial drugs. Dormant bacteria's physiology and the mechanism(s) used by bacteria to enter dormancy during infection are still unknown due to the lack of reliable animal models. However, several in vitro models, mimicking conditions encountered during infection, can reproduce different aspects of dormancy (growth arrest, metabolic slowdown, drug tolerance). The stringent response, a stress response program enabling bacteria to cope with nutrient starvation, is one of them. In this study, we provide evidence suggesting that the sigma factor SigE is not directly involved in the activation of stringent response as previously hypothesized, but it is important to help the bacteria to handle the metabolic stress related to the adaptation to low phosphate and activation of stringent response, thus giving an important contribution to our understanding of the mechanism behind stringent response development.
Collapse
Affiliation(s)
- Giacomo Baruzzo
- Department of Information Engineering, University of Padova, Padua, Italy
| | - Agnese Serafini
- Department of Molecular Medicine, University of Padova, Padua, Italy
| | | | - Tiziana Sanavia
- Department of Information Engineering, University of Padova, Padua, Italy
| | | | - Francesca Boldrin
- Department of Molecular Medicine, University of Padova, Padua, Italy
| | - Enrico Lavezzo
- Department of Molecular Medicine, University of Padova, Padua, Italy
| | - Luisa Barzon
- Department of Molecular Medicine, University of Padova, Padua, Italy
| | - Stefano Toppo
- Department of Molecular Medicine, University of Padova, Padua, Italy
| | | | | | - Barbara Di Camillo
- Department of Information Engineering, University of Padova, Padua, Italy
- Department of Comparative Biomedicine and Food Science, University of Padova, Padua, Italy
| |
Collapse
|
2
|
The polyHIS Tract of Yeast AMPK Coordinates Carbon Metabolism with Iron Availability. Int J Mol Sci 2023; 24:ijms24021368. [PMID: 36674878 PMCID: PMC9863760 DOI: 10.3390/ijms24021368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/06/2023] [Accepted: 01/07/2023] [Indexed: 01/13/2023] Open
Abstract
Energy status in all eukaryotic cells is sensed by AMP-kinases. We have previously found that the poly-histidine tract at the N-terminus of S. cerevisiae AMPK (Snf1) inhibits its function in the presence of glucose via a pH-regulated mechanism. We show here that in the absence of glucose, the poly-histidine tract has a second function, linking together carbon and iron metabolism. Under conditions of iron deprivation, when different iron-intense cellular systems compete for this scarce resource, Snf1 is inhibited. The inhibition is via an interaction of the poly-histidine tract with the low-iron transcription factor Aft1. Aft1 inhibition of Snf1 occurs in the nucleus at the nuclear membrane, and only inhibits nuclear Snf1, without affecting cytosolic Snf1 activities. Thus, the temporal and spatial regulation of Snf1 activity enables a differential response to iron depending upon the type of carbon source. The linkage of nuclear Snf1 activity to iron sufficiency ensures that sufficient clusters are available to support respiratory enzymatic activity and tests mitochondrial competency prior to activation of nuclear Snf1.
Collapse
|
3
|
Djoko K, Cavet J. Perspectives on Metals in Microbiology. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35786425 DOI: 10.1099/mic.0.001215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
- Karrera Djoko
- Department of Biosciences, Durham University, Durham, UK
| | - Jennifer Cavet
- School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK
| |
Collapse
|
4
|
Beste DJV. New perspectives on an ancient pathogen: thoughts for World Tuberculosis Day 2022. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 35357305 PMCID: PMC9558351 DOI: 10.1099/mic.0.001178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Dany J V Beste
- Department of Microbial Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, UK
| |
Collapse
|
5
|
Thomas GH. Microbial Musings – June 2021. Microbiology (Reading) 2021; 167. [DOI: 10.1099/mic.0.001077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|