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Fromm K, Boegli A, Ortelli M, Wagner A, Bohn E, Malmsheimer S, Wagner S, Dehio C. Bartonella taylorii: A Model Organism for Studying Bartonella Infection in vitro and in vivo. Front Microbiol 2022; 13:913434. [PMID: 35910598 PMCID: PMC9336547 DOI: 10.3389/fmicb.2022.913434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 05/05/2022] [Indexed: 11/13/2022] Open
Abstract
Bartonella spp. are Gram-negative facultative intracellular pathogens that infect diverse mammals and cause a long-lasting intra-erythrocytic bacteremia in their natural host. These bacteria translocate Bartonella effector proteins (Beps) into host cells via their VirB/VirD4 type 4 secretion system (T4SS) in order to subvert host cellular functions, thereby leading to the downregulation of innate immune responses. Most studies on the functional analysis of the VirB/VirD4 T4SS and the Beps were performed with the major zoonotic pathogen Bartonella henselae for which efficient in vitro infection protocols have been established. However, its natural host, the cat, is unsuitable as an experimental infection model. In vivo studies were mostly confined to rodent models using rodent-specific Bartonella species, while the in vitro infection protocols devised for B. henselae are not transferable for those pathogens. The disparities of in vitro and in vivo studies in different species have hampered progress in our understanding of Bartonella pathogenesis. Here we describe the murine-specific strain Bartonella taylorii IBS296 as a new model organism facilitating the study of bacterial pathogenesis both in vitro in cell cultures and in vivo in laboratory mice. We implemented the split NanoLuc luciferase-based translocation assay to study BepD translocation through the VirB/VirD4 T4SS. We found increased effector-translocation into host cells if the bacteria were grown on tryptic soy agar (TSA) plates and experienced a temperature shift immediately before infection. The improved infectivity in vitro was correlating to an upregulation of the VirB/VirD4 T4SS. Using our adapted infection protocols, we showed BepD-dependent immunomodulatory phenotypes in vitro. In mice, the implemented growth conditions enabled infection by a massively reduced inoculum without having an impact on the course of the intra-erythrocytic bacteremia. The established model opens new avenues to study the role of the VirB/VirD4 T4SS and the translocated Bep effectors in vitro and in vivo.
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Affiliation(s)
- Katja Fromm
- Biozentrum, University of Basel, Basel, Switzerland
| | - Alexandra Boegli
- Department of Biochemistry, Faculty of Biology and Medicine, Université de Lausanne, Epalinges, Switzerland
| | | | | | - Erwin Bohn
- Institute of Medical Microbiology and Hygiene, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Silke Malmsheimer
- Section of Cellular and Molecular Microbiology, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
| | - Samuel Wagner
- Section of Cellular and Molecular Microbiology, Interfaculty Institute of Microbiology and Infection Medicine (IMIT), University of Tübingen, Tübingen, Germany
- Excellence Cluster “Controlling Microbes to Fight Infections” (CMFI), Tübingen, Germany
- Partner-site Tübingen, German Center for Infection Research (DZIF), Tübingen, Germany
| | - Christoph Dehio
- Biozentrum, University of Basel, Basel, Switzerland
- *Correspondence: Christoph Dehio,
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Effects of NaCl Concentration on the Behavior of Vibrio brasiliensis and Transcriptome Analysis. Foods 2022; 11:foods11060840. [PMID: 35327263 PMCID: PMC8955013 DOI: 10.3390/foods11060840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 03/08/2022] [Accepted: 03/10/2022] [Indexed: 11/26/2022] Open
Abstract
The growth of Vibrio bacteria is affected by environmental conditions, and unfavorable conditions will produce different degrees of stress on Vibrio. The cells respond to the stress on the bacteria through changes in biological characteristics and transcriptomes. To study the effect of NaCl concentration on Vibrio brasiliensis, we have determined the biological characteristics of the 0%, 1%, 2%, 3%, 5%, and 7% NaCl concentrations cultured V. brasiliensis to research the salt stress to bacteria. We found that the biological properties of V. brasiliensis cultured with different NaCl concentrations were different, and the expression of outer membrane proteins of V. brasiliensis changed when it was grown under different NaCl concentrations. When bacteria cultured in higher NaCl concentrations (3%, 5% and 7% NaCl), the sodium-type flagellar protein MotY was found. Finally, the transcriptome analysis of V. brasiliensis cultured with 0% NaCl and 7% NaCl was carried out to find out the differentially expressed genes. We found that the same gene have opposite up-regulated and down-regulated expression in two treatments, indicating that these types of genes are regulated different in low and high osmotic stress.
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Gutiérrez R, Ram Y, Berman J, Carstens Marques de Sousa K, Nachum-Biala Y, Britzi M, Elad D, Glaser G, Covo S, Harrus S. Adaptive resistance mutations at supra-inhibitory concentrations independent of SOS mutagenesis. Mol Biol Evol 2021; 38:4095-4115. [PMID: 34175952 PMCID: PMC8476149 DOI: 10.1093/molbev/msab196] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Emergence of resistant bacteria during antimicrobial treatment is one of the most critical and universal health threats. It is known that several stress-induced mutagenesis and heteroresistance mechanisms can enhance microbial adaptation to antibiotics. Here, we demonstrate that the pathogen Bartonella can undergo stress-induced mutagenesis despite the fact it lacks error-prone polymerases, the rpoS gene and functional UV-induced mutagenesis. We demonstrate that Bartonella acquire de novo single mutations during rifampicin exposure at suprainhibitory concentrations at a much higher rate than expected from spontaneous fluctuations. This is while exhibiting a minimal heteroresistance capacity. The emerged resistant mutants acquired a single rpoB mutation, whereas no other mutations were found in their whole genome. Interestingly, the emergence of resistance in Bartonella occurred only during gradual exposure to the antibiotic, indicating that Bartonella sense and react to the changing environment. Using a mathematical model, we demonstrated that, to reproduce the experimental results, mutation rates should be transiently increased over 1,000-folds, and a larger population size or greater heteroresistance capacity is required. RNA expression analysis suggests that the increased mutation rate is due to downregulation of key DNA repair genes (mutS, mutY, and recA), associated with DNA breaks caused by massive prophage inductions. These results provide new evidence of the hazard of antibiotic overuse in medicine and agriculture.
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Affiliation(s)
- Ricardo Gutiérrez
- The Koret School of Veterinary Medicine, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel.,The Center for Research in Tropical Diseases, Faculty of Microbiology, University of Costa Rica, San José, Costa Rica
| | - Yoav Ram
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel.,School of Computer Science, Interdisciplinary Center Herzliya, Herzliya, Israel
| | - Judith Berman
- Shmunis School of Biomedicine and Cancer, Faculty of Life Sciences, Tel Aviv University, Tel Aviv University, Ramat Aviv, Israel
| | | | - Yaarit Nachum-Biala
- The Koret School of Veterinary Medicine, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Malka Britzi
- The National Residue Control Laboratory, The Kimron Veterinary Institute, Bet Dagan, Israel
| | - Daniel Elad
- Department of Clinical Bacteriology and Mycology, The Kimron Veterinary Institute, Bet Dagan, Israel
| | - Gad Glaser
- Department of Developmental Biology and Cancer Research, Institute for Medical Research Israel-Canada, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Shay Covo
- Department of Plant Pathology and Microbiology, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Shimon Harrus
- The Koret School of Veterinary Medicine, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel
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4
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Abstract
Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress. Bacteria must sense alterations in their environment and respond with changes in function and/or structure in order to cope. Extracytoplasmic function sigma factors (ECF σs) modulate transcription in response to cellular and environmental signals. The symbiotic nitrogen-fixing alphaproteobacterium Sinorhizobium meliloti carries genes for 11 ECF-like σs (RpoE1 to -E10 and FecI). We hypothesized that some of these play a role in mediating the interaction between the bacterium and its plant symbiotic partner. The bacterium senses changes in its immediate environment as it establishes contact with the plant root, initiates invasion of the plant as the root nodule is formed, traverses several root cell layers, and enters plant cortical cells via endocytosis. We used genetics, transcriptomics, and functionality to characterize the entire S. meliloti cohort of ECF σs. We discovered new targets for individual σs, confirmed others by overexpressing individual ECF σs, and identified or confirmed putative promoter motifs for nine of them. We constructed precise deletions of each ECF σ gene and its demonstrated or putative anti-σ gene and also a strain in which all 11 ECF σ and anti-σ genes were deleted. This all-ECF σ deletion strain showed no major defects in free-living growth, in Biolog Phenotype MicroArray assays, or in response to multiple stresses. None of the ECF σs were required for symbiosis on the host plants Medicago sativa and Medicago truncatula: the strain deleted for all ECF σ and anti-σ genes was symbiotically normal. IMPORTANCE Fixed (reduced) soil nitrogen plays a critical role in soil fertility and successful food growth. Much soil fertility relies on symbiotic nitrogen fixation: the bacterial partner infects the host plant roots and reduces atmospheric dinitrogen in exchange for host metabolic fuel, a process that involves complex interactions between the partners mediated by changes in gene expression in each partner. Here we test the roles of a family of 11 extracytoplasmic function (ECF) gene regulatory proteins (sigma factors [σs]) that interact with RNA polymerase to determine if they play a significant role in establishing a nitrogen-fixing symbiosis or in responding to various stresses, including cell envelope stress. We discovered that symbiotic nitrogen fixation occurs even when all 11 of these regulatory genes are deleted, that most ECF sigma factors control accessory functions, and that none of the ECF sigma factors are required to survive envelope stress.
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Ledermann R, Bartsch I, Müller B, Wülser J, Fischer HM. A Functional General Stress Response of Bradyrhizobium diazoefficiens Is Required for Early Stages of Host Plant Infection. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:537-547. [PMID: 29278144 DOI: 10.1094/mpmi-11-17-0284-r] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Phylogenetically diverse bacteria respond to various stress conditions by mounting a general stress response (GSR) resulting in the induction of protection or damage repair functions. In α-proteobacteria, the GSR is induced by a regulatory cascade consisting of the extracytoplasmic function (ECF) σ factor σEcfG, its anti-σ factor NepR, and the anti-anti-σ factor PhyR. We have reported previously that σEcfG and PhyR of Bradyrhizobium diazoefficiens (formerly named Bradyrhizobium japonicum), the nitrogen-fixing root nodule symbiont of soybean and related legumes, are required for efficient symbiosis; however, the precise role of the GSR remained undefined. Here, we analyze the symbiotic defects of a B. diazoefficiens mutant lacking σEcfG by comparing distinct infection stages of enzymatically or fluorescently tagged wild-type and mutant bacteria. Although root colonization and root hair curling were indistinguishable, the mutant was not competitive, and showed delayed development of emerging nodules and only a few infection threads. Consequently, many of the mutant-induced nodules were aborted, empty, or partially colonized. Congruent with these results, we found that σEcfG was active in bacteria present in root-hair-entrapped microcolonies and infection threads but not in root-associated bacteria and nitrogen-fixing bacteroids. We conclude that GSR-controlled functions are crucial for synchronization of infection thread formation, colonization, and nodule development.
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Affiliation(s)
- Raphael Ledermann
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Ilka Bartsch
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Barbara Müller
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Janine Wülser
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
| | - Hans-Martin Fischer
- ETH Zurich, Institute of Microbiology, Vladimir-Prelog-Weg 4, CH-8093 Zurich, Switzerland
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6
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Champion CJ, Xu J. The impact of metagenomic interplay on the mosquito redox homeostasis. Free Radic Biol Med 2017; 105:79-85. [PMID: 27880869 PMCID: PMC5401789 DOI: 10.1016/j.freeradbiomed.2016.11.031] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 11/02/2016] [Accepted: 11/17/2016] [Indexed: 10/20/2022]
Abstract
Mosquitoes are exposed to oxidative challenges throughout their life cycle. The primary challenge comes from a blood meal. The blood digestion turns the midgut into an oxidative environment, which imposes pressure not only on mosquito fecundity and other physiological traits but also on the microbiota in the midgut. During evolution, mosquitoes have developed numerous oxidative defense mechanisms to maintain redox homeostasis in the midgut. In addition to antioxidants, SOD, catalase, and glutathione system, sufficient supply of the reducing agent, NADPH, is vital for a successful defense against oxidative stress. Increasing evidence indicates that in response to oxidative stress, cells reconfigure metabolic pathways to increase the generation of NADPH through NADP-reducing networks including the pentose phosphate pathway and others. The microbial homeostasis is critical for the functional contributions to various host phenotypes. The symbiotic microbiota is regulated largely by the Duox-ROS pathway in Drosophila. In mosquitoes, Duox-ROS pathway, heme-mediated signaling, antimicrobial peptide production and C-type lectins work in concert to maintain the dynamic microbial community in the midgut. Microbial mechanisms against oxidative stress in this context are not well understood. Emerging evidence that microbial metabolites trigger host oxidative response warrants further study on the metagenomic interplay in an oxidative environment like mosquito gut ecosystem. Besides the classical Drosophila model, hematophagous insects like mosquitoes provide an alternative model system to study redox homeostasis in a symbiotic metagenomic context.
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Affiliation(s)
- Cody J Champion
- Biology Department, New Mexico State University, PO BOX 30001, MSC 3AF, Las Cruces, NM 88003, United States
| | - Jiannong Xu
- Biology Department, New Mexico State University, PO BOX 30001, MSC 3AF, Las Cruces, NM 88003, United States.
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7
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Rapid, Sensitive Detection of Bartonella quintana by Loop-Mediated Isothermal Amplification of the groEL Gene. Int J Mol Sci 2016; 17:ijms17121902. [PMID: 27916953 PMCID: PMC5187759 DOI: 10.3390/ijms17121902] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/08/2016] [Accepted: 11/10/2016] [Indexed: 01/27/2023] Open
Abstract
Trench fever, caused by Bartonella quintana, is recognized as a re-emerging and neglected disease. Rapid and sensitive detection approaches are urgently required to monitor and help control B. quintana infections. Here, loop-mediated isothermal amplification (LAMP), which amplifies target DNA at a fixed temperature with high sensitivity, specificity and rapidity, was employed to detect B. quintana. Thirty-six strains, including 10 B. quintana, 13 other Bartonella spp., and 13 other common pathogens, were applied to verify and evaluate the LAMP assay. The specificity of the LAMP assay was 100%, and the limit of detection was 125 fg/reaction. The LAMP assay was compared with qPCR in the examination of 100 rhesus and 20 rhesus-feeder blood samples; the diagnostic accuracy was found to be 100% when LAMP was compared to qPCR, but the LAMP assay was significantly more sensitive (p < 0.05). Thus, LAMP methodology is a useful for diagnosis of trench fever in humans and primates, especially in low-resource settings, because of its rapid, sensitive detection that does not require sophisticated equipment.
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8
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Tu N, Carroll RK, Weiss A, Shaw LN, Nicolas G, Thomas S, Lima A, Okaro U, Anderson B. A family of genus-specific RNAs in tandem with DNA-binding proteins control expression of the badA major virulence factor gene in Bartonella henselae. Microbiologyopen 2016; 6. [PMID: 27790856 PMCID: PMC5387305 DOI: 10.1002/mbo3.420] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 09/21/2016] [Accepted: 09/28/2016] [Indexed: 12/28/2022] Open
Abstract
Bartonella henselae is a gram‐negative zoonotic bacterium that causes infections in humans including endocarditis and bacillary angiomatosis. B. henselae has been shown to grow as large aggregates and form biofilms in vitro. The aggregative growth and the angiogenic host response requires the trimeric autotransporter adhesin BadA. We examined the transcriptome of the Houston‐1 strain of B. henselae using RNA‐seq revealing nine novel, highly‐expressed intergenic transcripts (Bartonella regulatory transcript, Brt1‐9). The Brt family of RNAs is unique to the genus Bartonella and ranges from 194 to 203 nucleotides with high homology and stable predicted secondary structures. Immediately downstream of each of the nine RNA genes is a helix‐turn‐helix DNA‐binding protein (transcriptional regulatory protein, Trp1‐9) that is poorly transcribed under the growth conditions used for RNA‐seq. Using knockdown or overexpressing strains, we show a role of both the Brt1 and Trp1 in the regulation of badA and also in biofilm formation. Based on these data, we hypothesize that Brt1 is a trans‐acting sRNA that also serves as a cis‐acting riboswitch to control the expression of badA. This family of RNAs together with the downstream Trp DNA‐binding proteins represents a novel coordinated regulatory circuit controlling expression of virulence‐associated genes in the bartonellae.
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Affiliation(s)
- Nhan Tu
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Ronan K Carroll
- Department of Biological Sciences, Ohio University, Athens, OH, USA
| | - Andy Weiss
- Department of Cellular, Molecular and Microbiology, College of Arts and Sciences, University of South Florida, Tampa, FL, USA
| | - Lindsey N Shaw
- Department of Cellular, Molecular and Microbiology, College of Arts and Sciences, University of South Florida, Tampa, FL, USA
| | - Gael Nicolas
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Sarah Thomas
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Amorce Lima
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Udoka Okaro
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
| | - Burt Anderson
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, USA
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9
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Willett JW, Herrou J, Czyz DM, Cheng JX, Crosson S. Brucella abortus ΔrpoE1 confers protective immunity against wild type challenge in a mouse model of brucellosis. Vaccine 2016; 34:5073-5081. [PMID: 27591954 DOI: 10.1016/j.vaccine.2016.08.076] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 08/22/2016] [Accepted: 08/26/2016] [Indexed: 11/28/2022]
Abstract
The Brucella abortus general stress response (GSR) system regulates activity of the alternative sigma factor, σ(E1), which controls transcription of approximately 100 genes and is required for persistence in a BALB/c mouse chronic infection model. We evaluated the host response to infection by a B. abortus strain lacking σ(E1) (ΔrpoE1), and identified pathological and immunological features that distinguish ΔrpoE1-infected mice from wild-type (WT), and that correspond with clearance of ΔrpoE1 from the host. ΔrpoE1 infection was indistinguishable from WT in terms of splenic bacterial burden, inflammation and histopathology up to 6weeks post-infection. However, Brucella-specific serum IgG levels in ΔrpoE1-infected mice were 5 times higher than WT by 4weeks post-infection, and remained significantly higher throughout the course of a 12-week infection. Total IgG and Brucella-specific IgG levels peaked strongly in ΔrpoE1-infected mice at 6weeks, which correlated with reduced splenomegaly and bacterial burden relative to WT-infected mice. Given the difference in immune response to infection with wild-type and ΔrpoE1, we tested whether ΔrpoE1 confers protective immunity to wild-type challenge. Mice immunized with ΔrpoE1 completely resisted WT infection and had significantly higher serum titers of Brucella-specific IgG, IgG2a and IFN-γ after WT challenge relative to age-matched naïve mice. We conclude that immunization of BALB/c mice with the B. abortus GSR pathway mutant, ΔrpoE1, elicits an adaptive immune response that confers significant protective immunity against WT infection.
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Affiliation(s)
- Jonathan W Willett
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA
| | - Julien Herrou
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA
| | - Daniel M Czyz
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA
| | - Jason X Cheng
- Department of Pathology, University of Chicago, Chicago, IL, USA
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA.,Department of Microbiology, University of Chicago, Chicago, IL, USA
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10
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Characterization of the general stress response in Bartonella henselae. Microb Pathog 2015; 92:1-10. [PMID: 26724735 DOI: 10.1016/j.micpath.2015.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/14/2015] [Accepted: 12/22/2015] [Indexed: 11/20/2022]
Abstract
Bacteria utilize a general stress response system to combat stresses from their surrounding environments. In alpha-proteobacteria, the general stress response uses an alternate sigma factor as the main regulator and incorporates it with a two-component system into a unique regulatory circuit. This system has been described in several alpha-proteobacterial species, including the pathogens Bartonella quintana and Brucella abortus. Most of the studies have focused on characterizing the PhyR anti-anti-sigma factor, the NepR anti-sigma factor, and the alternate sigma factor. However, not enough attention is directed toward studying the role of histidine kinases in the general stress response. Our study identifies the general stress response system in Bartonella henselae, where the gene synteny is conserved and both the PhyR and alternate sigma factor have similar sequence and domain structures with other alpha-proteobacteria. Our data showed that the general stress response genes are up-regulated under conditions that mimic the cat flea vector. Furthermore, we showed that both RpoE and PhyR positively regulate this system and that RpoE also affects transcription of genes encoding heme-binding proteins and the gene encoding the BadA adhesin. Finally, we identified a histidine kinase, annotated as BH13820 that can potentially phosphorylate PhyR.
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11
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Abstract
The Alphaproteobacteria uniquely integrate features of two-component signal transduction and alternative σ factor regulation to control transcription of genes that ensure growth and survival across a range of stress conditions. Research over the past decade has led to the discovery of the key molecular players of this general stress response (GSR) system, including the sigma factor σ(EcfG), its anti-σ factor NepR, and the anti-anti-σ factor PhyR. The central molecular event of GSR activation entails aspartyl phosphorylation of PhyR, which promotes its binding to NepR and thereby releases σ(EcfG) to associate with RNAP and direct transcription. Recent studies are providing a new understanding of complex, multilayered sensory networks that activate and repress this central protein partner switch. This review synthesizes our structural and functional understanding of the core GSR regulatory proteins and highlights emerging data that are defining the systems that regulate GSR transcription in a variety of species.
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Affiliation(s)
- Aretha Fiebig
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Julien Herrou
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Jonathan Willett
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637;
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12
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Abstract
The anti-σ factor NepR plays a central role in regulation of the general stress response (GSR) in alphaproteobacteria. This small protein has two known interaction partners: its cognate extracytoplasmic function (ECF) σ factor and the anti-anti-σ factor, PhyR. Stress-dependent phosphorylation of PhyR initiates a protein partner switch that promotes phospho-PhyR binding to NepR, which frees ECF σ to activate transcription of genes required for cell survival under adverse or fluctuating conditions. We have defined key functional roles for structured and intrinsically disordered domains of Caulobacter crescentus NepR in partner binding and activation of GSR transcription. We further demonstrate that NepR strongly stimulates the rate of PhyR phosphorylation in vitro and that this effect requires the structured and disordered domains of NepR. This result provides evidence for an additional layer of GSR regulation in which NepR directly influences activation of its binding partner, PhyR, as an anti-anti-σ factor. We conclude that structured and intrinsically disordered domains of NepR coordinately control multiple functions in the GSR signaling pathway, including core protein partner switch interactions and pathway activation by phosphorylation. Anti-σ factors are key molecular participants in a range of adaptive responses in bacteria. The anti-σ factor NepR plays a vital role in a multiprotein partner switch that governs general stress response (GSR) transcription in alphaproteobacteria. We have defined conserved and unconserved features of NepR structure that determine its function as an anti-σ factor and uncovered a functional role for intrinsically disordered regions of NepR in partner binding events required for GSR activation. We further demonstrate a novel function for NepR as an enhancer of PhyR phosphorylation; this activity also requires the disordered domains of NepR. Our results provide evidence for a new layer of GSR regulatory control in which NepR directly modulates PhyR phosphorylation and, hence, activation of the GSR.
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13
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The general stress response in Alphaproteobacteria. Trends Microbiol 2015; 23:164-71. [DOI: 10.1016/j.tim.2014.12.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/08/2014] [Accepted: 12/09/2014] [Indexed: 11/18/2022]
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14
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Sycz G, Carrica MC, Tseng TS, Bogomolni RA, Briggs WR, Goldbaum FA, Paris G. LOV Histidine Kinase Modulates the General Stress Response System and Affects the virB Operon Expression in Brucella abortus. PLoS One 2015; 10:e0124058. [PMID: 25993430 PMCID: PMC4438053 DOI: 10.1371/journal.pone.0124058] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 03/05/2015] [Indexed: 12/31/2022] Open
Abstract
Brucella is the causative agent of the zoonotic disease brucellosis, and its success as an intracellular pathogen relies on its ability to adapt to the harsh environmental conditions that it encounters inside the host. The Brucella genome encodes a sensor histidine kinase containing a LOV domain upstream from the kinase, LOVHK, which plays an important role in light-regulated Brucella virulence. In this report we study the intracellular signaling pathway initiated by the light sensor LOVHK using an integrated biochemical and genetic approach. From results of bacterial two-hybrid assays and phosphotransfer experiments we demonstrate that LOVHK functionally interacts with two response regulators: PhyR and LovR, constituting a functional two-component signal-transduction system. LOVHK contributes to the activation of the General Stress Response (GSR) system in Brucella via PhyR, while LovR is proposed to be a phosphate-sink for LOVHK, decreasing its phosphorylation state. We also show that in the absence of LOVHK the expression of the virB operon is down-regulated. In conclusion, our results suggest that LOVHK positively regulates the GSR system in vivo, and has an effect on the expression of the virB operon. The proposed regulatory network suggests a similar role for LOVHK in other microorganisms.
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Affiliation(s)
- Gabriela Sycz
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
| | - Mariela Carmen Carrica
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
| | - Tong-Seung Tseng
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California, United States of America
| | - Roberto A. Bogomolni
- Department of Chemistry and Biochemistry, University of California Santa Cruz, Santa Cruz, California, United States of America
| | - Winslow R. Briggs
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California, United States of America
| | - Fernando A. Goldbaum
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
| | - Gastón Paris
- Laboratorio de Inmunología y Microbiología Molecular, Fundación Instituto Leloir (IIBBA-CONICET), Buenos Aires, Argentina
- * E-mail:
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15
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Fu X, Liang W, Du P, Yan M, Kan B. Transcript changes in Vibrio cholerae in response to salt stress. Gut Pathog 2014; 6:47. [PMID: 25589902 PMCID: PMC4293811 DOI: 10.1186/s13099-014-0047-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 12/13/2014] [Indexed: 11/23/2022] Open
Abstract
Vibrio cholerae, which is a serious human intestinal pathogen, often resides and thrives in estuaries but requires major self-regulation to overcome intestinal hyperosmotic stress or high salt stress in water and food. In the present study, we selected multiple O1 and O139 group V. cholerae strains that were isolated from different regions and during different years to study their salt tolerance. Based on the mechanisms that other bacteria use to respond to high salt stress, we selected salt stress-response related genes to study the mechanisms which V. cholerae responds to high salt stress. V. cholerae strains showed salt-resistance characteristics that varied in salt concentrations from 4% to 6%. However, group O1 and group O139 showed no significant difference in the degree of salt tolerance. The primary responses of bacteria to salt stress, including Na+ exclusion, K+ uptake and glutamate biosynthesis, were observed in V. cholerae strains. In addition, some sigma factors were up-regulated in V. cholerae strains, suggesting that V. cholerae may recruit common sigma factors to achieve an active salt stress response. However, some changes in gene transcript levels in response to salt stress in V. cholerae were strain-specific. In particular, hierarchical clustering of differentially expressed genes indicated that transcript levels of these genes were correlated with the degree of salt tolerance. Therefore, elevated transcript levels of some genes, including sigma factors and genes involved in peptidoglycan biosynthesis, may be due to the salt tolerance of strains. In addition, high salt-tolerant strains may recruit common as well as additional sigma factors to activate the salt stress response.
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Affiliation(s)
- Xiuping Fu
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 155, Changbai Road, Changping, Beijing 102206 China ; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, 310006 China
| | - Weili Liang
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 155, Changbai Road, Changping, Beijing 102206 China ; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, 310006 China
| | - Pengcheng Du
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 155, Changbai Road, Changping, Beijing 102206 China ; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, 310006 China
| | - Meiying Yan
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 155, Changbai Road, Changping, Beijing 102206 China ; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, 310006 China
| | - Biao Kan
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 155, Changbai Road, Changping, Beijing 102206 China ; Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Hangzhou, 310006 China
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16
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Complex two-component signaling regulates the general stress response in Alphaproteobacteria. Proc Natl Acad Sci U S A 2014; 111:E5196-204. [PMID: 25404331 DOI: 10.1073/pnas.1410095111] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The general stress response (GSR) in Alphaproteobacteria was recently shown to be controlled by a partner-switching mechanism that is triggered by phosphorylation of the response regulator PhyR. Activation of PhyR ultimately results in release of the alternative extracytoplasmic function sigma factor σ(EcfG), which redirects transcription toward the GSR. Little is known about the signal transduction pathway(s) controlling PhyR phosphorylation. Here, we identified the single-domain response regulator (SDRR) SdrG and seven histidine kinases, PakA to PakG, belonging to the HWE/HisKA2 family as positive modulators of the GSR in Sphingomonas melonis Fr1. Phenotypic analyses, epistasis experiments, and in vitro phosphorylation assays indicate that Paks directly phosphorylate PhyR and SdrG, and that SdrG acts upstream of or in concert with PhyR, modulating its activity in a nonlinear pathway. Furthermore, we found that additional SDRRs negatively affect the GSR in a way that strictly requires PhyR and SdrG. Finally, analysis of GSR activation by thermal, osmotic, and oxidative stress indicates that Paks display different degrees of redundancy and that a specific kinase can sense multiple stresses, suggesting that the GSR senses a particular condition as a combination of, rather than individual, molecular cues. This study thus establishes the alphaproteobacterial GSR as a complex and interlinked network of two-component systems, in which multiple histidine kinases converge to PhyR, the phosphorylation of which is, in addition, subject to regulation by several SDRRs. Our finding that most HWE/HisKA2 kinases contribute to the GSR in S. melonis Fr1 opens the possibility that this notion might also be true for other Alphaproteobacteria.
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17
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Kim HS, Willett JW, Jain-Gupta N, Fiebig A, Crosson S. The Brucella abortus virulence regulator, LovhK, is a sensor kinase in the general stress response signalling pathway. Mol Microbiol 2014; 94:913-25. [PMID: 25257300 DOI: 10.1111/mmi.12809] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/23/2014] [Indexed: 12/11/2022]
Abstract
In the intracellular pathogen Brucella abortus, the general stress response (GSR) signalling system determines survival under acute stress conditions in vitro, and is required for long-term residence in a mammalian host. To date, the identity of the Brucella sensor kinase(s) that function to perceive stress and directly activate GSR signalling have remained undefined. We demonstrate that the flavin-binding sensor histidine kinase, LovhK (bab2_0652), functions as a primary B. abortus GSR sensor. LovhK rapidly and specifically phosphorylates the central GSR regulator, PhyR, and activates transcription of a set of genes that closely overlaps the known B. abortus GSR regulon. Deletion of lovhK severely compromises cell survival under defined oxidative and acid stress conditions. We further show that lovhK is required for cell survival during the early phase of mammalian cell infection and for establishment of long-term residence in a mouse infection model. Finally, we present evidence that particular regions of primary structure within the two N-terminal PAS domains of LovhK have distinct sensory roles under specific environmental conditions. This study elucidates new molecular components of a conserved signalling pathway that regulates B. abortus stress physiology and infection biology.
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Affiliation(s)
- Hye-Sook Kim
- The Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA; Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA
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18
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A putative bifunctional histidine kinase/phosphatase of the HWE family exerts positive and negative control on the Sinorhizobium meliloti general stress response. J Bacteriol 2014; 196:2526-35. [PMID: 24794560 DOI: 10.1128/jb.01623-14] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The EcfG-type sigma factor RpoE2 is the regulator of the general stress response in Sinorhizobium meliloti. RpoE2 activity is negatively regulated by two NepR-type anti-sigma factors (RsiA1/A2), themselves under the control of two anti-anti-sigma factors (RsiB1/B2) belonging to the PhyR family of response regulators. The current model of RpoE2 activation suggests that in response to stress, RsiB1/B2 are activated by phosphorylation of an aspartate residue in their receiver domain. Once activated, RsiB1/B2 become able to interact with the anti-sigma factors and release RpoE2, which can then associate with the RNA polymerase to transcribe its target genes. The purpose of this work was to identify and characterize proteins involved in controlling the phosphorylation status of RsiB1/B2. Using in vivo approaches, we show that the putative histidine kinase encoded by the rsiC gene (SMc01507), located downstream from rpoE2, is able to both positively and negatively regulate the general stress response. In addition, our data suggest that the negative action of RsiC results from inhibition of RsiB1/B2 phosphorylation. From these observations, we propose that RsiC is a bifunctional histidine kinase/phosphatase responsible for RsiB1/B2 phosphorylation or dephosphorylation in the presence or absence of stress, respectively. Two proteins were previously proposed to control PhyR phosphorylation in Caulobacter crescentus and Sphingomonas sp. strain FR1. However, these proteins contain a Pfam:HisKA_2 domain of dimerization and histidine phosphotransfer, whereas S. meliloti RsiC harbors a Pfam:HWE_HK domain instead. Therefore, this is the first report of an HWE_HK-containing protein controlling the general stress response in Alphaproteobacteria.
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Jans A, Vercruysse M, Gao S, Engelen K, Lambrichts I, Fauvart M, Michiels J. Canonical and non-canonical EcfG sigma factors control the general stress response in Rhizobium etli. Microbiologyopen 2013; 2:976-87. [PMID: 24311555 PMCID: PMC3892343 DOI: 10.1002/mbo3.137] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Revised: 09/16/2013] [Accepted: 09/23/2013] [Indexed: 01/14/2023] Open
Abstract
A core component of the α-proteobacterial general stress response (GSR) is the extracytoplasmic function (ECF) sigma factor EcfG, exclusively present in this taxonomic class. Half of the completed α-proteobacterial genome sequences contain two or more copies of genes encoding σEcfG-like sigma factors, with the primary copy typically located adjacent to genes coding for a cognate anti-sigma factor (NepR) and two-component response regulator (PhyR). So far, the widespread occurrence of additional, non-canonical σEcfG copies has not satisfactorily been explained. This study explores the hierarchical relation between Rhizobium etli σEcfG1 and σEcfG2, canonical and non-canonical σEcfG proteins, respectively. Contrary to reports in other species, we find that σEcfG1 and σEcfG2 act in parallel, as nodes of a complex regulatory network, rather than in series, as elements of a linear regulatory cascade. We demonstrate that both sigma factors control unique yet also shared target genes, corroborating phenotypic evidence. σEcfG1 drives expression of rpoH2, explaining the increased heat sensitivity of an ecfG1 mutant, while katG is under control of σEcfG2, accounting for reduced oxidative stress resistance of an ecfG2 mutant. We also identify non-coding RNA genes as novel σEcfG targets. We propose a modified model for GSR regulation in R. etli, in which σEcfG1 and σEcfG2 function largely independently. Based on a phylogenetic analysis and considering the prevalence of α-proteobacterial genomes with multiple σEcfG copies, this model may also be applicable to numerous other species.
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Affiliation(s)
- Ann Jans
- Centre of Microbial and Plant Genetics, KU Leuven, Heverlee, B-3001, Belgium
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20
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Québatte M, Dick MS, Kaever V, Schmidt A, Dehio C. Dual input control: activation of theBartonella henselae VirB/D4 type IV secretion system by the stringent sigma factor RpoH1 and the BatR/BatS two-component system. Mol Microbiol 2013; 90:756-75. [DOI: 10.1111/mmi.12396] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2013] [Indexed: 01/12/2023]
Affiliation(s)
- Maxime Québatte
- Focal Area Infection Biology, Biozentrum; University of Basel; Klingelbergstrasse 70 4056 Basel Switzerland
| | - Mathias S. Dick
- Focal Area Infection Biology, Biozentrum; University of Basel; Klingelbergstrasse 70 4056 Basel Switzerland
| | - Volkhard Kaever
- Research Core Unit for Mass Spectrometry - Metabolomics; Institute of Pharmacology; Hannover Medical School; Hannover Germany
| | - Alexander Schmidt
- Proteomics Core Facility, Biozentrum; University of Basel; Basel Switzerland
| | - Christoph Dehio
- Focal Area Infection Biology, Biozentrum; University of Basel; Klingelbergstrasse 70 4056 Basel Switzerland
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