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Pizzolato-Cezar LR, Spira B, Machini MT. Bacterial toxin-antitoxin systems: Novel insights on toxin activation across populations and experimental shortcomings. CURRENT RESEARCH IN MICROBIAL SCIENCES 2023; 5:100204. [PMID: 38024808 PMCID: PMC10643148 DOI: 10.1016/j.crmicr.2023.100204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023] Open
Abstract
The alarming rise in hard-to-treat bacterial infections is of great concern to human health. Thus, the identification of molecular mechanisms that enable the survival and growth of pathogens is of utmost urgency for the development of more efficient antimicrobial therapies. In challenging environments, such as presence of antibiotics, or during host infection, metabolic adjustments are essential for microorganism survival and competitiveness. Toxin-antitoxin systems (TASs) consisting of a toxin with metabolic modulating activity and a cognate antitoxin that antagonizes that toxin are important elements in the arsenal of bacterial stress defense. However, the exact physiological function of TA systems is highly debatable and with the exception of stabilization of mobile genetic elements and phage inhibition, other proposed biological functions lack a broad consensus. This review aims at gaining new insights into the physiological effects of TASs in bacteria and exploring the experimental shortcomings that lead to discrepant results in TAS research. Distinct control mechanisms ensure that only subsets of cells within isogenic cultures transiently develop moderate levels of toxin activity. As a result, TASs cause phenotypic growth heterogeneity rather than cell stasis in the entire population. It is this feature that allows bacteria to thrive in diverse environments through the creation of subpopulations with different metabolic rates and stress tolerance programs.
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Affiliation(s)
- Luis R. Pizzolato-Cezar
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Beny Spira
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - M. Teresa Machini
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
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Bartelds MW, García-Blay Ó, Verhagen PGA, Wubbolts EJ, van Sluijs B, Heus HA, de Greef TFA, Huck WTS, Hansen MMK. Noise Minimization in Cell-Free Gene Expression. ACS Synth Biol 2023; 12:2217-2225. [PMID: 37478000 PMCID: PMC10443034 DOI: 10.1021/acssynbio.3c00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Indexed: 07/23/2023]
Abstract
Biochemical reactions that involve small numbers of molecules are accompanied by a degree of inherent randomness that results in noisy reaction outcomes. In synthetic biology, the ability to minimize noise particularly during the reconstitution of future synthetic protocells is an outstanding challenge to secure robust and reproducible behavior. Here we show that by encapsulation of a bacterial cell-free gene expression system in water-in-oil droplets, in vitro-synthesized MazF reduces cell-free gene expression noise >2-fold. With stochastic simulations we identify that this noise minimization acts through both increased degradation and the autoregulatory feedback of MazF. Specifically, we find that the expression of MazF enhances the degradation rate of mRNA up to 18-fold in a sequence-dependent manner. This sequence specificity of MazF would allow targeted noise control, making it ideal to integrate into synthetic gene networks. Therefore, including MazF production in synthetic biology can significantly minimize gene expression noise, impacting future design principles of more complex cell-free gene circuits.
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Affiliation(s)
- Mart W. Bartelds
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Óscar García-Blay
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Pieter G. A. Verhagen
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Elise J. Wubbolts
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Bob van Sluijs
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Hans A. Heus
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Tom F. A. de Greef
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
- Laboratory
of Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Institute
for Complex Molecular Systems, Eindhoven
University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Computational
Biology Group, Department of Biomedical Engineering, Eindhoven University of Technology,
P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Center
for Living Technologies, Eindhoven-Wageningen-Utrecht
Alliance, 5600 MB Eindhoven, The Netherlands
| | - Wilhelm T. S. Huck
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
| | - Maike M. K. Hansen
- Institute
for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
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Berkvens A, Chauhan P, Bruggeman FJ. Integrative biology of persister cell formation: molecular circuitry, phenotypic diversification and fitness effects. JOURNAL OF THE ROYAL SOCIETY, INTERFACE 2022; 19:20220129. [PMID: 36099930 PMCID: PMC9470271 DOI: 10.1098/rsif.2022.0129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Microbial populations often contain persister cells, which reduce the extinction risk upon sudden stresses. Persister cell formation is deeply intertwined with physiology. Due to this complexity, it cannot be satisfactorily understood by focusing only on mechanistic, physiological or evolutionary aspects. In this review, we take an integrative biology perspective to identify common principles of persister cell formation, which might be applicable across evolutionary-distinct microbes. Persister cells probably evolved to cope with a fundamental trade-off between cellular stress and growth tasks, as any biosynthetic resource investment in growth-supporting proteins is at the expense of stress tasks and vice versa. Natural selection probably favours persister cell subpopulation formation over a single-phenotype strategy, where each cell is prepared for growth and stress to a suboptimal extent, since persister cells can withstand harsher environments and their coexistence with growing cells leads to a higher fitness. The formation of coexisting phenotypes requires bistable molecular circuitry. Bistability probably emerges from growth-modulated, positive feedback loops in the cell's growth versus stress control network, involving interactions between sigma factors, guanosine pentaphosphate and toxin-antitoxin (TA) systems. We conclude that persister cell formation is most likely a response to a sudden reduction in growth rate, which can be achieved by antibiotic addition, nutrient starvation, sudden stresses, nutrient transitions or activation of a TA system.
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Affiliation(s)
- Alicia Berkvens
- Systems Biology Lab, AIMMS, VU University, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
| | - Priyanka Chauhan
- Systems Biology Lab, AIMMS, VU University, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
| | - Frank J Bruggeman
- Systems Biology Lab, AIMMS, VU University, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands
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Nikolic N, Sauert M, Albanese TG, Moll I. Quantifying heterologous gene expression during ectopic MazF production in Escherichia coli. BMC Res Notes 2022; 15:173. [PMID: 35562780 PMCID: PMC9102682 DOI: 10.1186/s13104-022-06061-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 04/28/2022] [Indexed: 12/13/2022] Open
Abstract
Objective MazF is a sequence-specific endoribonuclease-toxin of the MazEF toxin–antitoxin system. MazF cleaves single-stranded ribonucleic acid (RNA) regions at adenine–cytosine–adenine (ACA) sequences in the bacterium Escherichia coli. The MazEF system has been used in various biotechnology and synthetic biology applications. In this study, we infer how ectopic mazF overexpression affects production of heterologous proteins. To this end, we quantified the levels of fluorescent proteins expressed in E. coli from reporters translated from the ACA-containing or ACA-less messenger RNAs (mRNAs). Additionally, we addressed the impact of the 5′-untranslated region of these reporter mRNAs under the same conditions by comparing expression from mRNAs that comprise (canonical mRNA) or lack this region (leaderless mRNA). Results Flow cytometry analysis indicates that during mazF overexpression, fluorescent proteins are translated from the canonical as well as leaderless mRNAs. Our analysis further indicates that longer mazF overexpression generally increases the concentration of fluorescent proteins translated from ACA-less mRNAs, however it also substantially increases bacterial population heterogeneity. Finally, our results suggest that the strength and duration of mazF overexpression should be optimized for each experimental setup, to maximize the heterologous protein production and minimize the amount of phenotypic heterogeneity in bacterial populations, which is unfavorable in biotechnological processes. Supplementary Information The online version contains supplementary material available at 10.1186/s13104-022-06061-9.
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Affiliation(s)
- Nela Nikolic
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria. .,Department of Microbiology, Immunobiology and Genetics, Max Perutz Labs, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria. .,Living Systems Institute, University of Exeter, Exeter, UK.
| | - Martina Sauert
- Department of Microbiology, Immunobiology and Genetics, Max Perutz Labs, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria
| | - Tanino G Albanese
- Department of Microbiology, Immunobiology and Genetics, Max Perutz Labs, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria
| | - Isabella Moll
- Department of Microbiology, Immunobiology and Genetics, Max Perutz Labs, Vienna Biocenter (VBC), University of Vienna, Vienna, Austria.
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Sulaiman JE, Lam H. Proteomic Investigation of Tolerant Escherichia coli Populations from Cyclic Antibiotic Treatment. J Proteome Res 2020; 19:900-913. [PMID: 31920087 DOI: 10.1021/acs.jproteome.9b00687] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Persisters are a subpopulation of cells that have enhanced abilities to survive antibiotics and other stressful conditions. Recently, it was found that when persisters were repeatedly regrown and retreated with the same antibiotic for several cycles, the new population will become tolerant to the drug. In this study, we applied such cyclic antibiotic treatment on Escherichia coli populations using different classes of antibiotics (ampicillin, ciprofloxacin, and apramycin) during the exponential phase. After a few cycles, we observed that the evolved populations exhibit high tolerance to the specific class of antibiotic used during the evolution experiments, which are achieved by single-point mutations in one or several genes. Interestingly, all evolved populations show multidrug tolerance at the stationary phase, indicating that they have higher triggered persister fraction. Proteomic analysis and cross-comparison of the regulated proteomes of the tolerant populations during the stationary phase identified protein candidates with similar expression profiles that might be important for the tolerance phenotype. Susceptibility tests of mutants lacking gene coding for these protein candidates showed that they have significantly reduced survival toward antibiotics not only during the stationary phase, but also during the exponential phase. We demonstrated how proteomics, combined with cyclic antibiotic treatment as a means to enrich tolerant populations, is a promising avenue to obtain fresh insights into the phenomenon of persistence.
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Affiliation(s)
- Jordy Evan Sulaiman
- Department of Chemical and Biological Engineering , The Hong Kong University of Science & Technology , Clear Water Bay , Kowloon 999077 , Hong Kong , China
| | - Henry Lam
- Department of Chemical and Biological Engineering , The Hong Kong University of Science & Technology , Clear Water Bay , Kowloon 999077 , Hong Kong , China
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Deciphering the Antitoxin-Regulated Bacterial Stress Response via Single-Cell Analysis. ACS Chem Biol 2019; 14:2859-2866. [PMID: 31670944 DOI: 10.1021/acschembio.9b00721] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Bacterial toxin-antitoxin (TA) systems, which are diverse and widespread among prokaryotes, are responsible for tolerance to drugs and environmental stresses. However, the low abundance of toxin and antitoxin proteins renders their quantitative measurement in single bacteria challenging. Employing a laboratory-built nano-flow cytometer (nFCM) to monitor a tetracysteine (TC)-tagged TA system labeled with the biarsenical dye FlAsH, we here report the development of a sensitive method that enables the detection of basal-level expression of antitoxin. Using the Escherichia coli MqsR/MqsA as a model TA system, we reveal for the first time that under its native promoter and in the absence of environmental stress, there exist two populations of bacteria with high or low levels of antitoxin MqsA. Under environmental stress, such as bile acid stress, heat shock, and amino acid starvation, the two populations of bacteria responded differently in terms of MqsA degradation and production. Subsequently, resumed production of MqsA after amino acid stress was observed for the first time. Taking advantage of the multiparameter capability of nFCM, bacterial growth rate and MqsA production were analyzed simultaneously. We found that under environmental stress, the response of bacterial growth was consistent with MqsA production but with an approximate 60 min lag. Overall, the results of the present study indicate that stochastic elevation of MqsA level facilitates bacterial survival, and the two populations with distinct phenotypes empower bacteria to deal with fluctuating environments. This analytical method will help researchers gain deeper insight into the heterogeneity and fundamental role of TA systems.
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Ferretti MB, Karbstein K. Does functional specialization of ribosomes really exist? RNA (NEW YORK, N.Y.) 2019; 25:521-538. [PMID: 30733326 PMCID: PMC6467006 DOI: 10.1261/rna.069823.118] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
It has recently become clear that ribosomes are much more heterogeneous than previously thought, with diversity arising from rRNA sequence and modifications, ribosomal protein (RP) content and posttranslational modifications (PTMs), as well as bound nonribosomal proteins. In some cases, the existence of these diverse ribosome populations has been verified by biochemical or structural methods. Furthermore, knockout or knockdown of RPs can diversify ribosome populations, while also affecting the translation of some mRNAs (but not others) with biological consequences. However, the effects on translation arising from depletion of diverse proteins can be highly similar, suggesting that there may be a more general defect in ribosome function or stability, perhaps arising from reduced ribosome numbers. Consistently, overall reduced ribosome numbers can differentially affect subclasses of mRNAs, necessitating controls for specificity. Moreover, in order to study the functional consequences of ribosome diversity, perturbations including affinity tags and knockouts are introduced, which can also affect the outcome of the experiment. Here we review the available literature to carefully evaluate whether the published data support functional diversification, defined as diverse ribosome populations differentially affecting translation of distinct mRNA (classes). Based on these observations and the commonly observed cellular responses to perturbations in the system, we suggest a set of important controls to validate functional diversity, which should include gain-of-function assays and the demonstration of inducibility under physiological conditions.
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Affiliation(s)
- Max B Ferretti
- Department of Integrative Structural and Molecular Biology, The Scripps Research Institute, Jupiter, Florida 33458, USA
- The Skaggs Graduate School of Chemical and Biological Sciences, The Scripps Research Institute, Jupiter, Florida 33458, USA
| | - Katrin Karbstein
- Department of Integrative Structural and Molecular Biology, The Scripps Research Institute, Jupiter, Florida 33458, USA
- The Skaggs Graduate School of Chemical and Biological Sciences, The Scripps Research Institute, Jupiter, Florida 33458, USA
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Nikolic N. Autoregulation of bacterial gene expression: lessons from the MazEF toxin-antitoxin system. Curr Genet 2019; 65:133-138. [PMID: 30132188 PMCID: PMC6343021 DOI: 10.1007/s00294-018-0879-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 08/13/2018] [Accepted: 08/14/2018] [Indexed: 11/30/2022]
Abstract
Autoregulation is the direct modulation of gene expression by the product of the corresponding gene. Autoregulation of bacterial gene expression has been mostly studied at the transcriptional level, when a protein acts as the cognate transcriptional repressor. A recent study investigating dynamics of the bacterial toxin-antitoxin MazEF system has shown how autoregulation at both the transcriptional and post-transcriptional levels affects the heterogeneity of Escherichia coli populations. Toxin-antitoxin systems hold a crucial but still elusive part in bacterial response to stress. This perspective highlights how these modules can also serve as a great model system for investigating basic concepts in gene regulation. However, as the genomic background and environmental conditions substantially influence toxin activation, it is important to study (auto)regulation of toxin-antitoxin systems in well-defined setups as well as in conditions that resemble the environmental niche.
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Affiliation(s)
- Nela Nikolic
- Institute of Science and Technology (IST) Austria, 3400, Klosterneuburg, Austria.
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Nikolic N, Bergmiller T, Vandervelde A, Albanese TG, Gelens L, Moll I. Autoregulation of mazEF expression underlies growth heterogeneity in bacterial populations. Nucleic Acids Res 2018; 46:2918-2931. [PMID: 29432616 PMCID: PMC5888573 DOI: 10.1093/nar/gky079] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 12/30/2017] [Accepted: 01/27/2018] [Indexed: 01/24/2023] Open
Abstract
The MazF toxin sequence-specifically cleaves single-stranded RNA upon various stressful conditions, and it is activated as a part of the mazEF toxin-antitoxin module in Escherichia coli. Although autoregulation of mazEF expression through the MazE antitoxin-dependent transcriptional repression has been biochemically characterized, less is known about post-transcriptional autoregulation, as well as how both of these autoregulatory features affect growth of single cells during conditions that promote MazF production. Here, we demonstrate post-transcriptional autoregulation of mazF expression dynamics by MazF cleaving its own transcript. Single-cell analyses of bacterial populations during ectopic MazF production indicated that two-level autoregulation of mazEF expression influences cell-to-cell growth rate heterogeneity. The increase in growth rate heterogeneity is governed by the MazE antitoxin, and tuned by the MazF-dependent mazF mRNA cleavage. Also, both autoregulatory features grant rapid exit from the stress caused by mazF overexpression. Time-lapse microscopy revealed that MazF-mediated cleavage of mazF mRNA leads to increased temporal variability in length of individual cells during ectopic mazF overexpression, as explained by a stochastic model indicating that mazEF mRNA cleavage underlies temporal fluctuations in MazF levels during stress.
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Affiliation(s)
- Nela Nikolic
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Tobias Bergmiller
- Institute of Science and Technology Austria (IST Austria), 3400 Klosterneuburg, Austria
| | - Alexandra Vandervelde
- Laboratory of Dynamics in Biological Systems, Department of Cellular and Molecular Medicine, University of Leuven, 3000 Leuven, Belgium
| | - Tanino G Albanese
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna BioCenter (VBC), 1030 Vienna, Austria
| | - Lendert Gelens
- Laboratory of Dynamics in Biological Systems, Department of Cellular and Molecular Medicine, University of Leuven, 3000 Leuven, Belgium
| | - Isabella Moll
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, University of Vienna, Vienna BioCenter (VBC), 1030 Vienna, Austria
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