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Urs K, Zimmern PE, Reitzer L. Abundant urinary amino acids activate glutamine synthetase-encoding glnA by two different mechanisms in Escherichia coli. J Bacteriol 2024; 206:e0037623. [PMID: 38358279 PMCID: PMC10955845 DOI: 10.1128/jb.00376-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 01/31/2024] [Indexed: 02/16/2024] Open
Abstract
Growth of uropathogenic Escherichia coli in the bladder induces transcription of glnA which codes for the ammonia-assimilating glutamine synthetase (GS) despite the normally suppressive high ammonia concentration. We previously showed that the major urinary component, urea, induces transcription from the Crp-dependent glnAp1 promoter, but the urea-induced transcript is not translated. Our purpose here was to determine whether the most abundant urinary amino acids, which are known to inhibit GS activity in vitro, also affect glnA transcription in vivo. We found that the abundant amino acids impaired growth, which glutamine and glutamate reversed; this implies inhibition of GS activity. In strains with deletions of crp and glnG that force transcription from the glnAp2 and glnAp1 promoters, respectively, we examined growth and glnA transcription with a glnA-gfp transcriptional fusion and quantitative reverse transcription PCR with primers that can distinguish transcription from the two promoters. The abundant urinary amino acids stimulated transcription from the glnAp2 promoter in the absence of urea but from the glnAp1 promoter in the presence of urea. However, transcription from glnAp1 did not produce a translatable mRNA or GS as assessed by a glnA-gfp translational fusion, enzymatic assay of GS, and Western blot to detect GS antigen in urea-containing media. We discuss these results within the context of the extremely rapid growth of uropathogenic E. coli in urine, the different factors that control the two glnA promoters and possible mechanisms that either overcome or bypass the urea-imposed block of glutamine synthesis during bacterial growth in urine.IMPORTANCEKnowledge of the regulatory mechanisms for genes expressed at the site of infection provides insight into the virulence of pathogenic bacteria. During urinary tract infections-most often caused by Escherichia coli-growth in urine induces the glnA gene which codes for glutamine synthetase. The most abundant urinary amino acids amplified the effect of urea which resulted in hypertranscription from the glnAp1 promoter and, unexpectedly, an untranslated transcript. E. coli must overcome this block in glutamine synthesis during growth in urine, and the mechanism of glutamine acquisition or synthesis may suggest a possible therapy.
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Affiliation(s)
- Karthik Urs
- Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Philippe E. Zimmern
- Department of Urology, University of Texas Southwestern Medical School, Dallas, Texas, USA
| | - Larry Reitzer
- Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA
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2
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Doranga S, Conway T. Nitrogen assimilation by E. coli in the mammalian intestine. mBio 2024; 15:e0002524. [PMID: 38380942 PMCID: PMC10936423 DOI: 10.1128/mbio.00025-24] [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: 01/10/2024] [Accepted: 01/17/2024] [Indexed: 02/22/2024] Open
Abstract
Nitrogen is an essential element for all living organisms, including Escherichia coli. Potential nitrogen sources are abundant in the intestine, but knowledge of those used specifically by E. coli to colonize remains limited. Here, we sought to determine the specific nitrogen sources used by E. coli to colonize the streptomycin-treated mouse intestine. We began by investigating whether nitrogen is limiting in the intestine. The NtrBC two-component system upregulates approximately 100 genes in response to nitrogen limitation. We showed that NtrBC is crucial for E. coli colonization, although most genes of the NtrBC regulon are not induced, which indicates that nitrogen is not limiting in the intestine. RNA-seq identified upregulated genes in colonized E. coli involved in transport and catabolism of seven amino acids, dipeptides and tripeptides, purines, pyrimidines, urea, and ethanolamine. Competitive colonization experiments revealed that L-serine, N-acetylneuraminic acid, N-acetylglucosamine, and di- and tripeptides serve as nitrogen sources for E. coli in the intestine. Furthermore, the colonization defect of a L-serine deaminase mutant was rescued by excess nitrogen in the drinking water but not by an excess of carbon and energy, demonstrating that L-serine serves primarily as a nitrogen source. Similar rescue experiments showed that N-acetylneuraminic acid serves as both a carbon and nitrogen source. To a minor extent, aspartate and ammonia also serve as nitrogen sources. Overall, these findings demonstrate that E. coli utilizes multiple nitrogen sources for successful colonization of the mouse intestine, the most important of which is L-serine. IMPORTANCE While much is known about the carbon and energy sources that are used by E. coli to colonize the mammalian intestine, very little is known about the sources of nitrogen. Interrogation of colonized E. coli by RNA-seq revealed that nitrogen is not limiting, indicating an abundance of nitrogen sources in the intestine. Pathways for assimilation of nitrogen from several amino acids, dipeptides and tripeptides, purines, pyrimidines, urea, and ethanolamine were induced in mice. Competitive colonization assays confirmed that mutants lacking catabolic pathways for L-serine, N-acetylneuraminic acid, N-acetylglucosamine, and di- and tripeptides had colonization defects. Rescue experiments in mice showed that L-serine serves primarily as a nitrogen source, whereas N-acetylneuraminic acid provides both carbon and nitrogen. Of the many nitrogen assimilation mutants tested, the largest colonization defect was for an L-serine deaminase mutant, which demonstrates L-serine is the most important nitrogen source for colonized E. coli.
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Affiliation(s)
- Sudhir Doranga
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
- Department of Cardiovascular and Metabolic Sciences, Cleveland Clinic, Cleveland, Ohio, USA
| | - Tyrrell Conway
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
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Fang F, Xue Y, Xu X, Fang D, Liu W, Zhong Y, Han J, Li Y, Tao Q, Lu R, Ma C, Kumar A, Wang D. L-glutamine protects against enterohemorrhagic Escherichia coli infection by inhibiting bacterial virulence and enhancing host defense concurrently. Microbiol Spectr 2023; 11:e0097523. [PMID: 37815335 PMCID: PMC10714755 DOI: 10.1128/spectrum.00975-23] [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: 03/07/2023] [Accepted: 08/24/2023] [Indexed: 10/11/2023] Open
Abstract
IMPORTANCE The type 3 secretion system (T3SS) was obtained in many Gram-negative bacterial pathogens, and it is crucial for their pathogenesis. Environmental signals were found to be involved in the expression regulation of T3SS, which was vital for successful bacterial infection in the host. Here, we discovered that L-glutamine (Gln), the most abundant amino acid in the human body, could repress enterohemorrhagic Escherichia coli (EHEC) T3SS expression via nitrogen metabolism and therefore had potential as an antivirulence agent. Our in vitro and in vivo evidence demonstrated that Gln could decline EHEC infection by attenuating bacterial virulence and enhancing host defense simultaneously. We repurpose Gln as a potential treatment for EHEC infection accordingly.
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Affiliation(s)
- Fang Fang
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Yunxin Xue
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Xuefang Xu
- State Key Laboratory of Infectious Disease Prevention and Control and National Institute for Communicable Diseases Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China
| | - Dingli Fang
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Weijia Liu
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Ying Zhong
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Jinping Han
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Yunhe Li
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Qian Tao
- Department of Pathology, Women and Children's Hospital, State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics, National Innovation Platform for Industry-Education Integration in Vaccine Research, Xiamen University, Xiamen, Fujian Province, China
| | - Rong Lu
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
| | - Cong Ma
- Department of Nephrology, Lishan Hospital, Anshan Central Hospital, Anshan, Liaoning Province, China
| | | | - Dai Wang
- Department of Laboratory Medicine, Xiamen Key Laboratory of Perinatal-Neonatal Infection, Women and Children's Hospital, State Key Laboratory of Vaccines for Infectious Diseases, Xiang An Biomedical Laboratory, School of Public Health and School of Medicine, Xiamen University, Xiamen, Fujian Province, China
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4
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North H, McLaughlin M, Fiebig A, Crosson S. The Caulobacter NtrB-NtrC two-component system bridges nitrogen assimilation and cell development. J Bacteriol 2023; 205:e0018123. [PMID: 37791753 PMCID: PMC10601693 DOI: 10.1128/jb.00181-23] [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: 06/07/2023] [Accepted: 09/03/2023] [Indexed: 10/05/2023] Open
Abstract
A suite of molecular sensory systems enables Caulobacter to control growth, development, and reproduction in response to levels of essential elements. The bacterial enhancer-binding protein (bEBP) NtrC and its cognate sensor histidine kinase, NtrB, are key regulators of nitrogen assimilation in many bacteria, but their roles in Caulobacter metabolism and development are not well defined. Notably, Caulobacter NtrC is an unconventional bEBP that lacks the σ54-interacting loop commonly known as the GAFTGA motif. Here we show that deletion of Caulobacter crescentus ntrC slows cell growth in complex medium and that ntrB and ntrC are essential when ammonium is the sole nitrogen source due to their requirement for glutamine synthetase expression. Random transposition of a conserved IS3-family mobile genetic element frequently rescued the growth defect of ntrC mutant strains by restoring transcription of the glnBA operon, revealing a possible role for IS3 transposition in shaping the evolution of Caulobacter populations during nutrient limitation. We further identified dozens of direct NtrC-binding sites on the C. crescentus chromosome, with a large fraction located near genes involved in polysaccharide biosynthesis. The majority of binding sites align with those of the essential nucleoid-associated protein, GapR, or the cell cycle regulator, MucR1. NtrC is therefore predicted to directly impact the regulation of cell cycle and cell development. Indeed, loss of NtrC function led to elongated polar stalks and elevated synthesis of cell envelope polysaccharides. This study establishes regulatory connections between NtrC, nitrogen metabolism, polar morphogenesis, and envelope polysaccharide synthesis in Caulobacter. IMPORTANCE Bacteria balance cellular processes with the availability of nutrients in their environment. The NtrB-NtrC two-component signaling system is responsible for controlling nitrogen assimilation in many bacteria. We have characterized the effect of ntrB and ntrC deletion on Caulobacter growth and development and uncovered a role for spontaneous IS element transposition in the rescue of transcriptional and nutritional deficiencies caused by ntrC mutation. We further defined the regulon of Caulobacter NtrC, a bacterial enhancer-binding protein, and demonstrate that it shares specific binding sites with essential proteins involved in cell cycle regulation and chromosome organization. Our work provides a comprehensive view of transcriptional regulation mediated by a distinctive NtrC protein, establishing its connection to nitrogen assimilation and developmental processes in Caulobacter.
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Affiliation(s)
- Hunter North
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Maeve McLaughlin
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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5
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North H, McLaughlin M, Fiebig A, Crosson S. The Caulobacter NtrB-NtrC two-component system bridges nitrogen assimilation and cell development. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.06.543975. [PMID: 37333394 PMCID: PMC10274813 DOI: 10.1101/2023.06.06.543975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
A suite of molecular sensory systems enables Caulobacter to control growth, development, and reproduction in response to levels of essential elements. The bacterial enhancer binding protein (bEBP) NtrC, and its cognate sensor histidine kinase NtrB, are key regulators of nitrogen assimilation in many bacteria, but their roles in Caulobacter metabolism and development are not well defined. Notably, Caulobacter NtrC is an unconventional bEBP that lacks the σ54-interacting loop commonly known as the GAFTGA motif. Here we show that deletion of C. crescentus ntrC slows cell growth in complex medium, and that ntrB and ntrC are essential when ammonium is the sole nitrogen source due to their requirement for glutamine synthetase (glnA) expression. Random transposition of a conserved IS3-family mobile genetic element frequently rescued the growth defect of ntrC mutant strains by restoring transcription of the glnBA operon, revealing a possible role for IS3 transposition in shaping the evolution of Caulobacter populations during nutrient limitation. We further identified dozens of direct NtrC binding sites on the C. crescentus chromosome, with a large fraction located near genes involved in polysaccharide biosynthesis. The majority of binding sites align with those of the essential nucleoid associated protein, GapR, or the cell cycle regulator, MucR1. NtrC is therefore predicted to directly impact the regulation of cell cycle and cell development. Indeed, loss of NtrC function led to elongated polar stalks and elevated synthesis of cell envelope polysaccharides. This study establishes regulatory connections between NtrC, nitrogen metabolism, polar morphogenesis, and envelope polysaccharide synthesis in Caulobacter .
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Affiliation(s)
- Hunter North
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
| | - Maeve McLaughlin
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
| | - Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan USA
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6
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Vogt SL, Serapio-Palacios A, Woodward SE, Santos AS, de Vries SP, Daigneault MC, Brandmeier LV, Grant AJ, Maskell DJ, Allen-Vercoe E, Finlay BB. Enterohemorrhagic Escherichia coli responds to gut microbiota metabolites by altering metabolism and activating stress responses. Gut Microbes 2023; 15:2190303. [PMID: 36951510 PMCID: PMC10038027 DOI: 10.1080/19490976.2023.2190303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 03/08/2023] [Indexed: 03/24/2023] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) is a major cause of severe bloody diarrhea, with potentially lethal complications, such as hemolytic uremic syndrome. In humans, EHEC colonizes the colon, which is also home to a diverse community of trillions of microbes known as the gut microbiota. Although these microbes and the metabolites that they produce represent an important component of EHEC's ecological niche, little is known about how EHEC senses and responds to the presence of gut microbiota metabolites. In this study, we used a combined RNA-Seq and Tn-Seq approach to characterize EHEC's response to metabolites from an in vitro culture of 33 human gut microbiota isolates (MET-1), previously demonstrated to effectively resolve recurrent Clostridioides difficile infection in human patients. Collectively, the results revealed that EHEC adjusts to growth in the presence of microbiota metabolites in two major ways: by altering its metabolism and by activating stress responses. Metabolic adaptations to the presence of microbiota metabolites included increased expression of systems for maintaining redox balance and decreased expression of biotin biosynthesis genes, reflecting the high levels of biotin released by the microbiota into the culture medium. In addition, numerous genes related to envelope and oxidative stress responses (including cpxP, spy, soxS, yhcN, and bhsA) were upregulated during EHEC growth in a medium containing microbiota metabolites. Together, these results provide insight into the molecular mechanisms by which pathogens adapt to the presence of competing microbes in the host environment, which ultimately may enable the development of therapies to enhance colonization resistance and prevent infection.
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Affiliation(s)
- Stefanie L. Vogt
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Sarah E. Woodward
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Andrew S. Santos
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Stefan P.W. de Vries
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Michelle C. Daigneault
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Lisa V. Brandmeier
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
| | - Andrew J. Grant
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Duncan J. Maskell
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Emma Allen-Vercoe
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - B. Brett Finlay
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
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7
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Characterization of the Role of Two-Component Systems in Antibiotic Resistance Formation in Salmonella enterica Serovar Enteritidis. mSphere 2022; 7:e0038322. [PMID: 36286534 PMCID: PMC9769886 DOI: 10.1128/msphere.00383-22] [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] [Indexed: 01/13/2023] Open
Abstract
The two-component system (TCS) is one of the primary pathways by which bacteria adapt to environmental stresses such as antibiotics. This study aimed to systematically explore the role of TCSs in the development of multidrug resistance (MDR) in Salmonella enterica serovar Enteritidis. Twenty-six in-frame deletion mutants of TCSs were generated from S. Enteritidis SJTUF12367 (the wild type [WT]). Antimicrobial susceptibility tests with these mutants revealed that 10 TCSs were involved in the development of antibiotic resistance in S. Enteritidis. In these 10 pairs of TCSs, functional defects in CpxAR, PhoPQ, and GlnGL in various S. Enteritidis isolates led to a frequent decrease in MIC values against at least three classes of clinically important antibiotics, including cephalosporins and quinolones, which indicated the importance of these TCSs to the formation of MDR. Interaction network analysis via STRING revealed that the genes cpxA, cpxR, phoP, and phoQ played important roles in the direct interaction with global regulatory genes and the relevant genes of efflux pumps and outer membrane porins. Quantitative reverse transcription-PCR analysis further demonstrated that the increased susceptibility to cephalosporins and quinolones in ΔphoP and ΔcpxR mutant cells was accompanied by increased expression of membrane porin genes (ompC, ompD, and ompF) and reduced expression of efflux pump genes (acrA, macB, and mdtK), as well as an adverse transcription of the global regulatory genes (ramA and crp). These results indicated that CpxAR and PhoPQ played an important role in the development of MDR in S. Enteritidis through regulation of cell membrane permeability and efflux pump activity. IMPORTANCE S. Enteritidis is a predominant Salmonella serotype that causes human salmonellosis and frequently exhibits high-level resistance to commonly used antibiotics, including cephalosporins and quinolones. Although TCSs are known as regulators for bacterial adaptation to stressful conditions, which modulates β-lactam resistance in Vibrio parahaemolyticus and colistin resistance in Salmonella enterica serovar Typhimurium, there is little knowledge of their functional mechanisms underlying the development of antibiotic resistance in S. Enteritidis. Here, we systematically identified the TCS elements in S. Enteritidis SJTUF12367, revealed that the three TCSs CpxAR, PhoPQ, and GlnGL were crucial for the MDR formation in S. Enteritidis, and preliminarily illustrated the regulatory functions of CpxAR and PhoPQ for antimicrobial resistance genes. Our work provides the basis to understand the important TCSs that regulate formation of antibiotic resistance in S. Enteritidis.
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8
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NtrC Increases Fitness of Salmonella enterica Serovar Typhimurium under Low and Fluctuating Nutrient Conditions. J Bacteriol 2022; 204:e0026422. [PMID: 36317920 PMCID: PMC9765038 DOI: 10.1128/jb.00264-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Enteric pathogens cycle between nutrient-rich host and nutrient-poor external environment. These pathogens compete for nutrients while cycling between host and external environment, and often experience starvation. In this context, we have studied the role of a global regulator (NtrC) of Salmonella Typhimurium. The ntrC knockout mutation caused extended lag phase (8 h) and slow growth in the minimal medium. In lag phase, the wild-type cells showed ~60-fold more expression of ntrC gene. Gene expression studies and biochemical assays showed that the extended lag phase and slow growth is due to slow metabolism, instead of nitrogen transport. Further, we observed that ntrC knockout mutation led extended lag phase and slow growth, made ΔntrC mutant unable to compete with wild-type S. Typhimurium in both static and fluctuating nutrient condition. In addition to this, ΔntrC knockout mutant was unable to survive long-term nitrogen starvation (150 days). The nutrient recycling assays and gene expression studies revealed that ntrC gene is essential for rapid recycling of nutrients from the dead cells. Moreover, in the absence of ntrC gene, magnesium limits the nutrient recycling efficiency of S. Typhimurium. Therefore, the ntrC gene, which is often studied with respect to nitrogen scavenging in a low nitrogen growing condition, is required even in the adequate supply of nitrogen to maintain optimal growth and fast exit from the lag phase. Hence, we conclude that, the ntrC expression is essential for competitive fitness of S. Typhimurium under the low and fluctuating nutrient condition. IMPORTANCE S. Typhimurium, both in host and external environment, faces enormous competition from other microorganisms. The competition may take place either in static or in fluctuating nutrient conditions. Thus, how S. Typhimurium survives under such overlapping stress conditions remained unclear. Therefore, using S. Typhimurium as model organism we report that a global regulator NtrC, found in enteric bacteria like Escherichia coli and Salmonella, activates the set of genes and operons involved in rapid adaptation and efficient nutrient recycling/scavenging. These properties enable cells to compete with other microbes under the characteristic feast-or-famine lifestyle of S. Typhimurium. Therefore, this work helps us to understand the starvation physiology of the enteric bacterial pathogen S. Typhimurium.
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9
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Molecular Origins of Transcriptional Heterogeneity in Diazotrophic Klebsiella oxytoca. mSystems 2022; 7:e0059622. [PMID: 36073804 PMCID: PMC9600154 DOI: 10.1128/msystems.00596-22] [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: 01/04/2023] Open
Abstract
Phenotypic heterogeneity in clonal bacterial batch cultures has been shown for a range of bacterial systems; however, the molecular origins of such heterogeneity and its magnitude are not well understood. Under conditions of extreme low-nitrogen stress in the model diazotroph Klebsiella oxytoca, we found remarkably high heterogeneity of nifHDK gene expression, which codes for the structural genes of nitrogenase, one key enzyme of the global nitrogen cycle. This heterogeneity limited the bulk observed nitrogen-fixing capacity of the population. Using dual-probe, single-cell RNA fluorescent in situ hybridization, we correlated nifHDK expression with that of nifLA and glnK-amtB, which code for the main upstream regulatory components. Through stochastic transcription models and mutual information analysis, we revealed likely molecular origins for heterogeneity in nitrogenase expression. In the wild type and regulatory variants, we found that nifHDK transcription was inherently bursty, but we established that noise propagation through signaling was also significant. The regulatory gene glnK had the highest discernible effect on nifHDK variance, while noise from factors outside the regulatory pathway were negligible. Understanding the basis of inherent heterogeneity of nitrogenase expression and its origins can inform biotechnology strategies seeking to enhance biological nitrogen fixation. Finally, we speculate on potential benefits of diazotrophic heterogeneity in natural soil environments. IMPORTANCE Nitrogen is an essential micronutrient for both plant and animal life and naturally exists in both reactive and inert chemical forms. Modern agriculture is heavily reliant on nitrogen that has been "fixed" into a reactive form via the energetically expensive Haber-Bosch process, with significant environmental consequences. Nitrogen-fixing bacteria provide an alternative source of fixed nitrogen for use in both biotechnological and agricultural settings, but this relies on a firm understanding of how the fixation process is regulated within individual bacterial cells. We examined the cell-to-cell variability in the nitrogen-fixing behavior of Klebsiella oxytoca, a free-living bacterium. The significance of our research is in identifying not only the presence of marked variability but also the specific mechanisms that give rise to it. This understanding gives insight into both the evolutionary advantages of variable behavior as well as strategies for biotechnological applications.
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10
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Walling LR, Kouse AB, Shabalina SA, Zhang H, Storz G. A 3' UTR-derived small RNA connecting nitrogen and carbon metabolism in enteric bacteria. Nucleic Acids Res 2022; 50:10093-10109. [PMID: 36062564 DOI: 10.1093/nar/gkac748] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 08/11/2022] [Accepted: 08/26/2022] [Indexed: 11/13/2022] Open
Abstract
Increasing numbers of small, regulatory RNAs (sRNAs) corresponding to 3' untranslated regions (UTR) are being discovered in bacteria. One such sRNA, denoted GlnZ, corresponds to the 3' UTR of the Escherichia coli glnA mRNA encoding glutamine synthetase. Several forms of GlnZ, processed from the glnA mRNA, are detected in cells growing with limiting ammonium. GlnZ levels are regulated transcriptionally by the NtrC transcription factor and post-transcriptionally by RNase III. Consistent with the expression, E. coli cells lacking glnZ show delayed outgrowth from nitrogen starvation compared to wild type cells. Transcriptome-wide RNA-RNA interactome datasets indicated that GlnZ binds to multiple target RNAs. Immunoblots and assays of fusions confirmed GlnZ-mediated repression of glnP and sucA, encoding proteins that contribute to glutamine transport and the citric acid cycle, respectively. Although the overall sequences of GlnZ from E. coli K-12, Enterohemorrhagic E. coli and Salmonella enterica have significant differences due to various sequence insertions, all forms of the sRNA were able to regulate the two targets characterized. Together our data show that GlnZ impacts growth of E. coli under low nitrogen conditions by modulating genes that affect carbon and nitrogen flux.
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Affiliation(s)
- Lauren R Walling
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-4417, USA
| | - Andrew B Kouse
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-4417, USA
| | - Svetlana A Shabalina
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - Hongen Zhang
- Bioinformatics and Scientific Programming Core, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-4417, USA
| | - Gisela Storz
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892-4417, USA
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Prochlorococcus Exudate Stimulates Heterotrophic Bacterial Competition with Rival Phytoplankton for Available Nitrogen. mBio 2022; 13:e0257121. [PMID: 35012332 PMCID: PMC8749424 DOI: 10.1128/mbio.02571-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The marine cyanobacterium Prochlorococcus numerically dominates the phytoplankton community of the nutrient-limited open ocean, establishing itself as the most abundant photosynthetic organism on Earth. This ecological success has been attributed to lower cell quotas for limiting nutrients, superior resource acquisition, and other advantages associated with cell size reduction and genome streamlining. In this study, we tested the prediction that Prochlorococcus outcompetes its rivals for scarce nutrients and that this advantage leads to its numerical success in nutrient-limited waters. Strains of Prochlorococcus and its sister genus Synechococcus grew well in both mono- and cocultures when nutrients were replete. However, in nitrogen-limited medium, Prochlorococcus outgrew Synechococcus but only when heterotrophic bacteria were also present. In the nitrogen-limited medium, the heterotroph Alteromonas macleodii outcompeted Synechococcus for nitrogen but only if stimulated by the exudate released by Prochlorococcus or if a proxy organic carbon source was provided. Genetic analysis of Alteromonas suggested that it outcompetes Synechococcus for nitrate and/or nitrite, during which cocultured Prochlorococcus grows on ammonia or other available nitrogen species. We propose that Prochlorococcus can stimulate antagonism between heterotrophic bacteria and potential phytoplankton competitors through a metabolic cross-feeding interaction, and this stimulation could contribute to the numerical success of Prochlorococcus in nutrient-limited regions of the ocean. IMPORTANCE In nutrient-poor habitats, competition for limited resources is thought to select for organisms with an enhanced ability to scavenge nutrients and utilize them efficiently. Such adaptations characterize the cyanobacterium Prochlorococcus, the most abundant photosynthetic organism in the nutrient-limited open ocean. In this study, the competitive superiority of Prochlorococcus over a rival cyanobacterium, Synechococcus, was captured in laboratory culture. Critically, this outcome was achieved only when key aspects of the open ocean were simulated: a limited supply of nitrogen and the presence of heterotrophic bacteria. The results indicate that Prochlorococcus promotes its numerical dominance over Synechococcus by energizing the heterotroph's ability to outcompete Synechococcus for available nitrogen. This study demonstrates how interactions between trophic groups can influence interactions within trophic groups and how these interactions likely contribute to the success of the most abundant photosynthetic microorganism.
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12
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Miyakoshi M, Morita T, Kobayashi A, Berger A, Takahashi H, Gotoh Y, Hayashi T, Tanaka K. Glutamine synthetase mRNA releases sRNA from its 3'UTR to regulate carbon/nitrogen metabolic balance in Enterobacteriaceae. eLife 2022; 11:82411. [PMID: 36440827 PMCID: PMC9731577 DOI: 10.7554/elife.82411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 11/27/2022] [Indexed: 11/29/2022] Open
Abstract
Glutamine synthetase (GS) is the key enzyme of nitrogen assimilation induced under nitrogen limiting conditions. The carbon skeleton of glutamate and glutamine, 2-oxoglutarate, is supplied from the TCA cycle, but how this metabolic flow is controlled in response to nitrogen availability remains unknown. We show that the expression of the E1o component of 2-oxoglutarate dehydrogenase, SucA, is repressed under nitrogen limitation in Salmonella enterica and Escherichia coli. The repression is exerted at the post-transcriptional level by an Hfq-dependent sRNA GlnZ generated from the 3'UTR of the GS-encoding glnA mRNA. Enterobacterial GlnZ variants contain a conserved seed sequence and primarily regulate sucA through base-pairing far upstream of the translation initiation region. During growth on glutamine as the nitrogen source, the glnA 3'UTR deletion mutants expressed SucA at higher levels than the S. enterica and E. coli wild-type strains, respectively. In E. coli, the transcriptional regulator Nac also participates in the repression of sucA. Lastly, this study clarifies that the release of GlnZ from the glnA mRNA by RNase E is essential for the post-transcriptional regulation of sucA. Thus, the mRNA coordinates the two independent functions to balance the supply and demand of the fundamental metabolites.
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Affiliation(s)
- Masatoshi Miyakoshi
- Department of Infection Biology, Faculty of Medicine, University of TsukubaTsukubaJapan,Transborder Medical Research Center, University of TsukubaTsukubaJapan,International Joint Degree Master’s Program in Agro-Biomedical Science in Food and Health (GIP-TRIAD), University of TsukubaTsukubaJapan
| | - Teppei Morita
- Institute for Advanced Biosciences, Keio UniversityTsuruokaJapan,Graduate School of Media and Governance, Keio UniversityFujisawaJapan
| | - Asaki Kobayashi
- Transborder Medical Research Center, University of TsukubaTsukubaJapan
| | - Anna Berger
- International Joint Degree Master’s Program in Agro-Biomedical Science in Food and Health (GIP-TRIAD), University of TsukubaTsukubaJapan
| | | | - Yasuhiro Gotoh
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu UniversityFukuokaJapan
| | - Tetsuya Hayashi
- Department of Bacteriology, Faculty of Medical Sciences, Kyushu UniversityFukuokaJapan
| | - Kan Tanaka
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of TechnologyYokohamaJapan
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13
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Nolan C, Behrends V. Sub-Inhibitory Antibiotic Exposure and Virulence in Pseudomonas aeruginosa. Antibiotics (Basel) 2021; 10:antibiotics10111393. [PMID: 34827331 PMCID: PMC8615142 DOI: 10.3390/antibiotics10111393] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/09/2021] [Accepted: 11/10/2021] [Indexed: 12/20/2022] Open
Abstract
Pseudomonas aeruginosa is a prime opportunistic pathogen, one of the most important causes of hospital-acquired infections and the major cause of morbidity and mortality in cystic fibrosis lung infections. One reason for the bacterium's pathogenic success is the large array of virulence factors that it can employ. Another is its high degree of intrinsic and acquired resistance to antibiotics. In this review, we first summarise the current knowledge about the regulation of virulence factor expression and production. We then look at the impact of sub-MIC antibiotic exposure and find that the virulence-antibiotic interaction for P. aeruginosa is antibiotic-specific, multifaceted, and complex. Most studies undertaken to date have been in vitro assays in batch culture systems, involving short-term (<24 h) antibiotic exposure. Therefore, we discuss the importance of long-term, in vivo-mimicking models for future work, particularly highlighting the need to account for bacterial physiology, which by extension governs both virulence factor expression and antibiotic tolerance/resistance.
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Master regulator NtrC controls the utilization of alternative nitrogen sources in Pseudomonas stutzeri A1501. World J Microbiol Biotechnol 2021; 37:177. [PMID: 34524580 PMCID: PMC8443478 DOI: 10.1007/s11274-021-03144-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 09/07/2021] [Indexed: 11/25/2022]
Abstract
Pseudomonas stutzeri A1501 is a model strain used to study associative nitrogen fixation, and it possesses the nitrogen regulatory NtrC protein in the core genome. Nitrogen sources represent one of the important factors affecting the efficiency of biological nitrogen fixation in the natural environment. However, the regulation of NtrC during nitrogen metabolism in P. stutzeri A1501 has not been clarified. In this work, a phenotypic analysis of the ntrC mutant characterized the roles of NtrC in nitrogen metabolism and the oxidative stress response of P. stutzeri A1501. To systematically identify NtrC-controlled gene expression, RNA-seq was performed to further analyse the gene expression differences between the wild-type strain and the ∆ntrC mutant under nitrogen fixation conditions. A total of 1431 genes were found to be significantly altered by ntrC deletion, among which 147 associative genes had NtrC-binding sites, and the pathways for nitrogen fixation regulation, nitrogenous compound acquisition and catabolism and nitrate assimilation were discussed. Furthermore, the oxidative stress-related gene (katB), which was upregulated by ntrC deletion, was suggested to be a potential target gene of NtrC, thus highlighting the importance of NtrC in nitrogenase protection against oxygen damage. Based on these findings, we propose that NtrC is a high-ranking element in the regulatory network of P. stutzeri A1501 that controls a variety of nitrogen metabolic and oxidative stress responsive traits required for adaptation to complex rhizosphere environments.
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15
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Waite CJ, Lindström Battle A, Bennett MH, Carey MR, Hong CK, Kotta-Loizou I, Buck M, Schumacher J. Resource Allocation During the Transition to Diazotrophy in Klebsiella oxytoca. Front Microbiol 2021; 12:718487. [PMID: 34434180 PMCID: PMC8381380 DOI: 10.3389/fmicb.2021.718487] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Accepted: 07/12/2021] [Indexed: 11/13/2022] Open
Abstract
Free-living nitrogen-fixing bacteria can improve growth yields of some non-leguminous plants and, if enhanced through bioengineering approaches, have the potential to address major nutrient imbalances in global crop production by supplementing inorganic nitrogen fertilisers. However, nitrogen fixation is a highly resource-costly adaptation and is de-repressed only in environments in which sources of reduced nitrogen are scarce. Here we investigate nitrogen fixation (nif) gene expression and nitrogen starvation response signaling in the model diazotroph Klebsiella oxytoca (Ko) M5a1 during ammonium depletion and the transition to growth on atmospheric N2. Exploratory RNA-sequencing revealed that over 50% of genes were differentially expressed under diazotrophic conditions, among which the nif genes are among the most highly expressed and highly upregulated. Isotopically labelled QconCAT standards were designed for multiplexed, absolute quantification of Nif and nitrogen-stress proteins via multiple reaction monitoring mass spectrometry (MRM-MS). Time-resolved Nif protein concentrations were indicative of bifurcation in the accumulation rates of nitrogenase subunits (NifHDK) and accessory proteins. We estimate that the nitrogenase may account for more than 40% of cell protein during diazotrophic growth and occupy approximately half the active ribosome complement. The concentrations of free amino acids in nitrogen-starved cells were insufficient to support the observed rates of Nif protein expression. Total Nif protein accumulation was reduced 10-fold when the NifK protein was truncated and nitrogenase catalysis lost (nifK1–1203), implying that reinvestment of de novo fixed nitrogen is essential for further nif expression and a complete diazotrophy transition. Several amino acids accumulated in non-fixing ΔnifLA and nifK1–1203 mutants, while the rest remained highly stable despite prolonged N starvation. Monitoring post-translational uridylylation of the PII-type signaling proteins GlnB and GlnK revealed distinct nitrogen regulatory roles in Ko M5a1. GlnK uridylylation was persistent throughout the diazotrophy transition while a ΔglnK mutant exhibited significantly reduced Nif expression and nitrogen fixation activity. Altogether, these findings highlight quantitatively the scale of resource allocation required to enable the nitrogen fixation adaptation to take place once underlying signaling processes are fulfilled. Our work also provides an omics-level framework with which to model nitrogen fixation in free-living diazotrophs and inform rational engineering strategies.
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Affiliation(s)
- Christopher J Waite
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | | | - Mark H Bennett
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Matthew R Carey
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Chun K Hong
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Ioly Kotta-Loizou
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Martin Buck
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Jörg Schumacher
- Department of Life Sciences, Imperial College London, London, United Kingdom
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16
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Kim YJ, Choi BJ, Park SH, Lee HB, Son JE, Choi U, Chi WJ, Lee CR. Distinct Amino Acid Availability-Dependent Regulatory Mechanisms of MepS and MepM Levels in Escherichia coli. Front Microbiol 2021; 12:677739. [PMID: 34276609 PMCID: PMC8278236 DOI: 10.3389/fmicb.2021.677739] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 05/28/2021] [Indexed: 12/17/2022] Open
Abstract
Peptidoglycan (PG) hydrolases play important roles in various aspects of bacterial physiology, including cytokinesis, PG synthesis, quality control of PG, PG recycling, and antibiotic resistance. However, the regulatory mechanisms of their expression are poorly understood. In this study, we have uncovered novel regulatory mechanisms of the protein levels of the synthetically lethal PG endopeptidases MepS and MepM, which are involved in PG synthesis. A mutant defective for both MepS and MepM was lethal in an amino acid-rich medium, whereas it exhibited almost normal growth in a minimal medium, suggesting the expendability of MepS and MepM in a minimal medium. Protein levels of MepS and MepM dramatically decreased in the minimal medium. Although MepM was revealed as a substrate of Prc, a periplasmic protease involved in the proteolysis of MepS, only the decrease in the MepS level in the minimal medium was affected by the prc depletion. Phenotypic and biochemical analyses showed that the presence of aromatic amino acids in the medium induced the accumulation of MepS, but not MepM, while the presence of glutamate increased the level of MepM, but not MepS. Together, these results demonstrate that the protein levels of the two major PG endopeptidases are regulated in an amino acid availability-dependent manner, but their molecular mechanisms and signaling are significantly distinct.
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Affiliation(s)
- Yung Jae Kim
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Byoung Jun Choi
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Si Hyoung Park
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Han Byeol Lee
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Ji Eun Son
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Umji Choi
- Department of Biological Sciences, Myongji University, Yongin, South Korea
| | - Won-Jae Chi
- Biological and Genetic Resource Assessment Division, National Institute of Biological Resource, Incheon, South Korea
| | - Chang-Ro Lee
- Department of Biological Sciences, Myongji University, Yongin, South Korea
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17
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Naren N, Zhang XX. Role of a local transcription factor in governing cellular carbon/nitrogen homeostasis in Pseudomonas fluorescens. Nucleic Acids Res 2021; 49:3204-3216. [PMID: 33675669 PMCID: PMC8034625 DOI: 10.1093/nar/gkab091] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 12/14/2022] Open
Abstract
Autoactivation of two-component systems (TCSs) can increase the sensitivity to signals but inherently cause a delayed response. Here, we describe a unique negative feedback mechanism enabling the global NtrB/NtrC regulator to rapidly respond to nitrogen starvation over the course of histidine utilization (hut) in Pseudomonas fluorescens. NtrBC directly activates transcription of hut genes, but overexpression will produce excess ammonium leading to NtrBC inactivation. To prevent this from occurring, the histidine-responsive repressor HutC fine-tunes ntrBC autoactivation: HutC and NtrC bind to the same operator site in the ntrBC promoter. This newly discovered low-affinity binding site shows little sequence similarity with the consensus sequence that HutC recognizes for substrate-specific induction of hut operons. A combination of genetic and transcriptomic analysis indicated that both ntrBC and hut promoter activities cannot be stably maintained in the ΔhutC background when histidine fluctuates at high concentrations. Moreover, the global carbon regulator CbrA/CbrB is involved in directly activating hut transcription while de-repressing hut translation via the CbrAB-CrcYZ-Crc/Hfq regulatory cascade. Together, our data reveal that the local transcription factor HutC plays a crucial role in governing NtrBC to maintain carbon/nitrogen homeostasis through the complex interactions between two TCSs (NtrBC and CbrAB) at the hut promoter.
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Affiliation(s)
- Naran Naren
- School of Natural and Computational Sciences, Massey University at Albany, Auckland 0745, New Zealand
| | - Xue-Xian Zhang
- School of Natural and Computational Sciences, Massey University at Albany, Auckland 0745, New Zealand
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18
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A Novel Small RNA Promotes Motility and Virulence of Enterohemorrhagic Escherichia coli O157:H7 in Response to Ammonium. mBio 2021; 12:mBio.03605-20. [PMID: 33688013 PMCID: PMC8092317 DOI: 10.1128/mbio.03605-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The process by which bacteria sense environmental cues to regulate their virulence is complex. Several studies have focused on regulating the expression of the locus of enterocyte effacement pathogenicity island in the typical gut pathogenic bacterium, O157. Enterohemorrhagic Escherichia coli serotype O157:H7 (O157) is a critical, foodborne, human intestinal pathogen that causes severe acute hemorrhagic diarrhea, abdominal cramping, and even death. Small RNAs (sRNAs) are noncoding regulatory molecules that sense environmental changes and trigger various virulence-related signaling pathways; however, few such sRNAs have been identified in O157. Here, we report a novel sRNA, EsrF that senses high ammonium concentrations in the colon and enhances O157 pathogenicity by promoting bacterial motility and adhesion to host cells. Specifically, EsrF was found to directly interact with the 5′ untranslated regions of the flagellar biosynthetic gene, flhB, mRNA and increase its abundance, thereby upregulating expression of essential flagellar genes, including flhD, flhC, fliA, and fliC, leading to elevated O157 motility and virulence. Meanwhile, an infant rabbit model of O157 infection showed that deletion of esrF and flhB significantly attenuates O157 pathogenicity. Furthermore, NtrC—the response regulator of the NtrC/B two-component system—was found to exert direct, negative regulation of esrF expression. Meanwhile, high ammonium concentrations in the colon release the inhibitory effect of NtrC on esrF, thereby enhancing its expression and subsequently promoting bacterial colonization in the host colon. Our work reveals a novel, sRNA-centered, virulence-related signaling pathway in O157 that senses high ammonium concentrations. These findings provide novel insights for future research on O157 pathogenesis and targeted treatment strategies.
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19
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McQuail J, Switzer A, Burchell L, Wigneshweraraj S. The RNA-binding protein Hfq assembles into foci-like structures in nitrogen starved Escherichia coli. J Biol Chem 2020; 295:12355-12367. [PMID: 32532816 PMCID: PMC7458820 DOI: 10.1074/jbc.ra120.014107] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/09/2020] [Indexed: 11/13/2022] Open
Abstract
The initial adaptive responses to nutrient depletion in bacteria often occur at the level of gene expression. Hfq is an RNA-binding protein present in diverse bacterial lineages that contributes to many different aspects of RNA metabolism during gene expression. Using photoactivated localization microscopy and single-molecule tracking, we demonstrate that Hfq forms a distinct and reversible focus-like structure in Escherichia coli specifically experiencing long-term nitrogen starvation. Using the ability of T7 phage to replicate in nitrogen-starved bacteria as a biological probe of E. coli cell function during nitrogen starvation, we demonstrate that Hfq foci have a role in the adaptive response of E. coli to long-term nitrogen starvation. We further show that Hfq foci formation does not depend on gene expression once nitrogen starvation has set in and occurs indepen-dently of the transcription factor N-regulatory protein C, which activates the initial adaptive response to N starvation in E. coli These results serve as a paradigm to demonstrate that bacterial adaptation to long-term nutrient starvation can be spatiotemporally coordinated and can occur independently of de novo gene expression during starvation.
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Affiliation(s)
- Josh McQuail
- Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - Amy Switzer
- Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - Lynn Burchell
- Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
| | - Sivaramesh Wigneshweraraj
- Medical Research Council Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom
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20
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The Adaptive Response to Long-Term Nitrogen Starvation in Escherichia coli Requires the Breakdown of Allantoin. J Bacteriol 2020; 202:JB.00172-20. [PMID: 32571968 PMCID: PMC7417836 DOI: 10.1128/jb.00172-20] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Accepted: 06/15/2020] [Indexed: 01/08/2023] Open
Abstract
Bacteria initially respond to nutrient starvation by eliciting large-scale transcriptional changes. The accompanying changes in gene expression and metabolism allow the bacterial cells to effectively adapt to the nutrient-starved state. How the transcriptome subsequently changes as nutrient starvation ensues is not well understood. We used nitrogen (N) starvation as a model nutrient starvation condition to study the transcriptional changes in Escherichia coli experiencing long-term N starvation. The results reveal that the transcriptome of N-starved E. coli undergoes changes that are required to maximize chances of viability and to effectively recover growth when N starvation conditions become alleviated. We further reveal that, over time, N-starved E. coli cells rely on the degradation of allantoin for optimal growth recovery when N becomes replenished. This study provides insights into the temporally coordinated adaptive responses that occur in E. coli experiencing sustained N starvation.IMPORTANCE Bacteria in their natural environments seldom encounter conditions that support continuous growth. Hence, many bacteria spend the majority of their time in states of little or no growth due to starvation of essential nutrients. To cope with prolonged periods of nutrient starvation, bacteria have evolved several strategies, primarily manifesting themselves through changes in how the information in their genes is accessed. How these coping strategies change over time under nutrient starvation is not well understood, and this knowledge is important not only to broaden our understanding of bacterial cell function but also to potentially find ways to manage harmful bacteria. This study provides insights into how nitrogen-starved Escherichia coli bacteria rely on different genes during long-term nitrogen starvation.
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21
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Yu C, Nguyen DP, Ren Z, Liu J, Yang F, Tian F, Fan S, Chen H. The RpoN2-PilRX regulatory system governs type IV pilus gene transcription and is required for bacterial motility and virulence in Xanthomonas oryzae pv. oryzae. MOLECULAR PLANT PATHOLOGY 2020; 21:652-666. [PMID: 32112711 PMCID: PMC7170775 DOI: 10.1111/mpp.12920] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 01/22/2020] [Accepted: 01/24/2020] [Indexed: 06/10/2023]
Abstract
The type IV pilus (T4P), a special class of bacterial surface filament, plays crucial roles in surface adhesion, motility, biofilm formation, and virulence in pathogenic bacteria. However, the regulatory mechanism of T4P and its relationship to bacterial virulence are still little understood in Xanthomonas oryzae pv. oryzae (Xoo), the causal pathogen of bacterial blight of rice. Our previous studies showed that the σ54 factor RpoN2 regulated bacterial virulence on rice in a flagellum-independent manner in Xoo. In this study, both yeast two-hybrid and pull-down assays revealed that RpoN2 directly and specifically interacted with PilRX, a homolog of the response regulator PilR of the two-component system PilS-PilR in the pilus gene cluster. Genomic sequence and reverse transcription PCR (RT-PCR) analysis showed 13 regulons containing 25 genes encoding T4P structural components and putative regulators. A consensus RpoN2-binding sequence GGN10 GC was identified in the promoter sequences of most T4P gene transcriptional units. Electrophoretic mobility shift assays confirmed the direct binding of RpoN2 to the promoter of the major pilin gene pilAX, the inner membrane platform protein gene pilCX, and pilRX. Promoter activity and quantitative RT-PCR assays demonstrated direct and indirect transcriptional regulation by RpoN2 of the T4P genes. In addition, individual deletions of pilAX, pilCX, and pilRX resulted in significantly reduced twitching and swimming motility, biofilm formation, and virulence in rice. Taken together, the findings from the current study suggest that the RpoN2-PilRX regulatory system controls bacterial motility and virulence by regulating T4P gene transcription in Xoo.
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Affiliation(s)
- Chao Yu
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Doan-Phuong Nguyen
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Zhaoyu Ren
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Jianan Liu
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Fenghuan Yang
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Fang Tian
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
| | - Susu Fan
- Shandong Provincial Key Laboratory of Applied MicrobiologyEcology InstituteQilu University of Technology (Shandong Academy of Sciences)Ji’nanChina
| | - Huamin Chen
- State Key Laboratory for Biology of Plant Diseases and Insect PestsInstitute of Plant ProtectionChinese Academy of Agricultural SciencesBeijingChina
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22
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Global control of bacterial nitrogen and carbon metabolism by a PTS Ntr-regulated switch. Proc Natl Acad Sci U S A 2020; 117:10234-10245. [PMID: 32341157 DOI: 10.1073/pnas.1917471117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The nitrogen-related phosphotransferase system (PTSNtr) of Rhizobium leguminosarum bv. viciae 3841 transfers phosphate from PEP via PtsP and NPr to two output regulators, ManX and PtsN. ManX controls central carbon metabolism via the tricarboxylic acid (TCA) cycle, while PtsN controls nitrogen uptake, exopolysaccharide production, and potassium homeostasis, each of which is critical for cellular adaptation and survival. Cellular nitrogen status modulates phosphorylation when glutamine, an abundant amino acid when nitrogen is available, binds to the GAF sensory domain of PtsP, preventing PtsP phosphorylation and subsequent modification of ManX and PtsN. Under nitrogen-rich, carbon-limiting conditions, unphosphorylated ManX stimulates the TCA cycle and carbon oxidation, while unphosphorylated PtsN stimulates potassium uptake. The effects are reversed with the phosphorylation of ManX and PtsN, occurring under nitrogen-limiting, carbon-rich conditions; phosphorylated PtsN triggers uptake and nitrogen metabolism, the TCA cycle and carbon oxidation are decreased, while carbon-storage polymers such as surface polysaccharide are increased. Deleting the GAF domain from PtsP makes cells "blind" to the cellular nitrogen status. PTSNtr constitutes a switch through which carbon and nitrogen metabolism are rapidly, and reversibly, regulated by protein:protein interactions. PTSNtr is widely conserved in proteobacteria, highlighting its global importance.
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23
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Hay AE, Herrera-Belaroussi A, Rey M, Fournier P, Normand P, Boubakri H. Feedback Regulation of N Fixation in Frankia-Alnus Symbiosis Through Amino Acids Profiling in Field and Greenhouse Nodules. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:499-508. [PMID: 31916486 DOI: 10.1094/mpmi-10-19-0289-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Symbiosis established between actinorhizal plants and Frankia spp., which are nitrogen-fixing actinobacteria, promotes nodule organogenesis, the site of metabolic exchange. The present study aimed to identify amino acid markers involved in Frankia-Alnus interactions by comparing nodules and associated roots from field and greenhouse samples. Our results revealed a high level of citrulline in all samples, followed by arginine (Arg), aspartate (Asp), glutamate (Glu), γ-amino-n-butyric acid (GABA), and alanine (Ala). Interestingly, the field metabolome approach highlighted more contrasted amino acid patterns between nodules and roots compared with greenhouse samples. Indeed, 12 amino acids had a mean relative abundance significantly different between field nodule and root samples, against only four amino acids in greenhouse samples, underlining the importance of developing "ecometabolome" approaches. In order to monitor the effects on Frankia cells (respiration and nitrogen fixation activities) of amino acid with an abundance pattern evocative of a role in symbiosis, in-vitro assays were performed by supplementing them in nitrogen-free cultures. Amino acids had three types of effects: i) those used by Frankia as nitrogen source (Glu, Gln, Asp), ii) amino acids stimulating both nitrogen fixation and respiration (e.g., Cit, GABA, Ala, valine, Asn), and iii) amino acids triggering a toxic effect (Arg, histidine). In this paper, a N-metabolic model was proposed to discuss how the host plant and bacteria modulate amino acids contents in nodules, leading to a fine regulation sustaining high bacterial nitrogen fixation.
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Affiliation(s)
- Anne-Emmanuelle Hay
- Université de Lyon, F-69361, Lyon, France, Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, F-69622, Villeurbanne, France
- Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, Centre d'Etude des Substances Naturelles
| | - Aude Herrera-Belaroussi
- Université de Lyon, F-69361, Lyon, France, Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, F-69622, Villeurbanne, France
| | - Marjolaine Rey
- Université de Lyon, F-69361, Lyon, France, Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, F-69622, Villeurbanne, France
- Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, Centre d'Etude des Substances Naturelles
| | - Pascale Fournier
- Université de Lyon, F-69361, Lyon, France, Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, F-69622, Villeurbanne, France
| | - Philippe Normand
- Université de Lyon, F-69361, Lyon, France, Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, F-69622, Villeurbanne, France
| | - Hasna Boubakri
- Université de Lyon, F-69361, Lyon, France, Université Claude Bernard Lyon 1, CNRS, UMR 5557, INRA UMR1418, Ecologie Microbienne, F-69622, Villeurbanne, France
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Gao Q, Su S, Li X, Wang H, Liu J, Gao S. Transcriptional analysis of RstA/RstB in avian pathogenic Escherichia coli identifies its role in the regulation of hdeD-mediated virulence and survival in chicken macrophages. Vet Microbiol 2019; 241:108555. [PMID: 31928702 DOI: 10.1016/j.vetmic.2019.108555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/16/2019] [Accepted: 12/17/2019] [Indexed: 10/25/2022]
Abstract
Avian pathogenic Escherichia coli (APEC) causes avian colibacillosis in poultry, which is characterized by systemic infections such as septicemia, air sacculitis, and pericarditis. APEC uses two-component regulatory systems (TCSs) to handle the stressful environments present in infected hosts. While many TCSs in E. coli have been well characterized, the RstA/RstB system in APEC has not been thoroughly investigated. The involvement of the RstA regulator in APEC pathogenesis was demonstrated during previous studies investigating its role in APEC persistence in chicken macrophages and respiratory infections. However, the mechanism underlying this phenomenon has not been clarified. Transcriptional analysis of the effect of rstAB deletion was therefore performed to improve the understanding of the RstA/RstB regulatory mechanism, and particularly its role in virulence. The transcriptomes of the rstAB mutant and the wild-type strain E058 were compared during their growth in the bloodstreams of challenged chickens. Overall, 198 differentially expressed (DE) genes were identified, and these indicated that RstA/RstB mainly regulates systems involved in nitrogen metabolism, iron acquisition, and acid resistance. Phenotypic assays indicated that the rstAB mutant responded more to an acidic pH than the wild-type strain did, possibly because of the repression of the acid-resistance operons hdeABD and gadABE by the deletion of rstAB. Based on the reported RstA box motif TACATNTNGTTACA, we identified four possible RstA target genes (hdeD, fadE, narG, and metE) among the DE genes. An electrophoretic mobility shift assay confirmed that RstA binds directly to the promoter of hdeD, and β-galactosidase assays showed that hdeD expression was reduced by rstAB deletion, indicating that RstA directly regulates hdeD expression. The hdeD mutation resulted in virulence attenuation in both cultured chicken macrophages and experimentally infected chickens. In conclusion, our data suggest that RstA affects APEC E058 virulence partly by directly regulating the acidic resistance gene hdeD.
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Affiliation(s)
- Qingqing Gao
- Animal Infectious Disease Laboratory, Ministry of Agriculture, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China
| | - Senyan Su
- Animal Infectious Disease Laboratory, Ministry of Agriculture, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China
| | - Xi Li
- Animal Infectious Disease Laboratory, Ministry of Agriculture, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China
| | - Hang Wang
- Animal Infectious Disease Laboratory, Ministry of Agriculture, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China
| | - Jinbiao Liu
- Animal Infectious Disease Laboratory, Ministry of Agriculture, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China
| | - Song Gao
- Animal Infectious Disease Laboratory, Ministry of Agriculture, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, PR China.
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Abstract
Global (metabolic) regulatory networks allow microorganisms to survive periods of nitrogen starvation or general nutrient stress. Uptake and utilization of various nitrogen sources are thus commonly tightly regulated in Prokarya (Bacteria and Archaea) in response to available nitrogen sources. Those well-studied regulations occur mainly at the transcriptional and posttranslational level. Surprisingly, and in contrast to their involvement in most other stress responses, small RNAs (sRNAs) involved in the response to environmental nitrogen fluctuations are only rarely reported. In addition to sRNAs indirectly affecting nitrogen metabolism, only recently it was demonstrated that three sRNAs were directly involved in regulation of nitrogen metabolism in response to changes in available nitrogen sources. All three trans-acting sRNAs are under direct transcriptional control of global nitrogen regulators and affect expression of components of nitrogen metabolism (glutamine synthetase, nitrogenase, and PII-like proteins) by either masking the ribosome binding site and thus inhibiting translation initiation or stabilizing the respective target mRNAs. Most likely, there are many more sRNAs and other types of noncoding RNAs, e.g., riboswitches, involved in the regulation of nitrogen metabolism in Prokarya that remain to be uncovered. The present review summarizes the current knowledge on sRNAs involved in nitrogen metabolism and their biological functions and targets.
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Nitrogen Starvation Induces Persister Cell Formation in Escherichia coli. J Bacteriol 2019; 201:JB.00622-18. [PMID: 30420451 DOI: 10.1128/jb.00622-18] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 11/02/2018] [Indexed: 01/23/2023] Open
Abstract
To cope with fluctuations in their environment, bacteria have evolved multiple adaptive stress responses. One such response is the nitrogen regulation stress response, which allows bacteria, such as Escherichia coli, to cope with and overcome conditions of nitrogen limitation. This response is directed by the two-component system NtrBC, where NtrC acts as the major transcriptional regulator to activate the expression of genes to mount the response. Recently, my colleagues and I showed that NtrC directly regulates the expression of the relA gene, the major (p)ppGpp synthetase in E. coli, coupling the nitrogen regulation stress and stringent responses. As elevated levels of (p)ppGpp have been implicated in the formation of persister cells, here, I investigated whether nitrogen starvation promotes their formation and whether the NtrC-RelA regulatory cascade plays a role. The results reveal that nitrogen-starved E. coli synthesizes (p)ppGpp and forms a higher percentage of persister cells than nonstarved cells and that both NtrC and RelA are important for these processes. This study provides novel insights into how the formation of persisters can be promoted in response to a nutritional stress.IMPORTANCE Bacteria often reside in environments where nutrient availability is scarce; therefore, they have evolved adaptive responses to rapidly cope with conditions of feast and famine. Understanding the mechanisms that underpin the regulation of how bacteria cope with this stress is a fundamentally important question in the wider context of understanding the biology of the bacterial cell and bacterial pathogenesis. Two major adaptive mechanisms to cope with starvation are the nitrogen regulation (ntr) stress and stringent responses. Here, I describe how these bacterial stress responses are coordinated under conditions of nitrogen starvation to promote the formation of antibiotic-tolerant persister cells by elevating levels of the secondary messenger (p)ppGpp.
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The deuridylylation activity of Herbaspirillum seropedicae GlnD protein is regulated by the glutamine:2-oxoglutarate ratio. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:1216-1223. [DOI: 10.1016/j.bbapap.2018.09.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 09/22/2018] [Accepted: 09/25/2018] [Indexed: 11/21/2022]
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Biosensors-Based In Vivo Quantification of 2-Oxoglutarate in Cyanobacteria and Proteobacteria. Life (Basel) 2018; 8:life8040051. [PMID: 30373229 PMCID: PMC6315671 DOI: 10.3390/life8040051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/24/2018] [Accepted: 10/25/2018] [Indexed: 01/12/2023] Open
Abstract
2-oxoglutarate (α-ketoglutarate; 2-OG) is an intermediate of the Krebs cycle, and constitutes the carbon skeleton for nitrogen assimilation and the synthesis of a variety of compounds. In addition to being an important metabolite, 2-OG is a signaling molecule with a broad regulatory repertoire in a variety of organisms, including plants, animals, and bacteria. Although challenging, measuring the levels and variations of metabolic signals in vivo is critical to better understand how cells control specific processes. To measure cellular 2-OG concentrations and dynamics, we designed a set of biosensors based on the fluorescence resonance energy transfer (FRET) technology that can be used in vivo in different organisms. For this purpose, we took advantage of the conformational changes of two cyanobacterial proteins induced by 2-OG binding. We show that these biosensors responded immediately and specifically to different 2-OG levels, and hence allowed to measure 2-OG variations in function of environmental modifications in the proteobacterium Escherichia coli and in the cyanobacterium Anabaena sp. PCC 7120. Our results pave the way to study 2-OG dynamics at the cellular level in uni- and multi-cellular organisms.
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Chen S, Zhou Q, Tan X, Li Y, Ren G, Wang X. The Global Response of Cronobacter sakazakii Cells to Amino Acid Deficiency. Front Microbiol 2018; 9:1875. [PMID: 30154778 PMCID: PMC6102319 DOI: 10.3389/fmicb.2018.01875] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 07/25/2018] [Indexed: 12/29/2022] Open
Abstract
Cronobacter species can cause necrotizing enterocolitis and meningitis in neonates and infants, their infection is closely relevant to their responses to extreme growth conditions. In this study, the response of Cronobacter species to amino acid deficiency has been investigated. Four Cronobacter species formed smooth colonies when grown on the solid LB medium, but formed mucoid colonies when grown on the amino acid deficient M9 medium. When the mucoid colonies were stained with tannin mordant, exopolysaccharide around the cells could be discerned. The exopolysaccharide was isolated, analyzed, and identified as colanic acid. When genes wcaD and wcaE relevant to colanic acid biosynthesis were deleted in Cronobacter sakazakii BAA-894, no exopolysaccharide could be produced, confirming the exopolysaccharide formed in C. sakazakii grown in M9 is colanic acid. On the other hand, when genes rcsA, rcsB, rcsC, rcsD, or rcsF relevant to Rcs phosphorelay system was deleted in C. sakazakii BAA-894, colanic acid could not be produced, suggesting that the production of colanic acid in C. sakazakii is regulated by Rcs phosphorelay system. Furthermore, C. sakazakii BAA-894 grown in M9 supplemented with amino acids could not produce exopolysaccharide. Transcriptomes of C. sakazakii BAA-894 grown in M9 or LB were analyzed. A total of 3956 genes were differentially expressed in M9, of which 2339 were up-regulated and 1617 were down-regulated. When C. sakazakii BAA-894 was grown in M9, the genes relevant to the biosynthesis of exopolysaccharide were significantly up-regulated; on the other hand, the genes relevant to the flagellum formation and chemotaxis were significantly down-regulated; in addition, most genes relevant to various amino acid biosynthesis were also significantly regulated. The results demonstrate that amino acid deficiency has a global impact on C. sakazakii cells.
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Affiliation(s)
- Si Chen
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Qing Zhou
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Xin Tan
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
| | - Ye Li
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Ge Ren
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Xiaoyuan Wang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
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Castro NSS, Laia CAT, Maiti BK, Cerqueira NMFSA, Moura I, Carepo MSP. Small phospho-donors phosphorylate MorR without inducing protein conformational changes. Biophys Chem 2018; 240:25-33. [PMID: 29883882 DOI: 10.1016/j.bpc.2018.05.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/10/2018] [Accepted: 05/29/2018] [Indexed: 10/14/2022]
Abstract
Phosphorylation is an essential mechanism of protein control and plays an important role in biology. The two-component system (TCS) is a bacterial regulation mechanism mediated by a response regulator (RR) protein and a kinase protein, which synchronize the regulatory circuit according to the environment. Phosphorylation is a key element in TCS function as it controls RR activity. In the present study, we characterize the behavior of MorR, an RR associated with Mo homeostasis, upon acetylphosphate and phosphoramidate treatment in vitro. Our results show that MorR was phosphorylated by both phospho-donors. Fluorescence experiments showed that MorR tryptophan emission is quenched by phosphoramidate. Furthermore, theoretical and computational results demonstrate that phosphorylation by phosphoramidate is more favorable than that by acetylphosphate. In conclusion, phosphorylated MorR is a monomeric protein and phosphorylation does not appear to induce observable conformational changes in the protein structure.
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Affiliation(s)
- Nathália S S Castro
- LAQV-REQUIMTE, Departamento de Química, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
| | - César A T Laia
- REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
| | - Biplab K Maiti
- LAQV-REQUIMTE, Departamento de Química, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Nuno M F S A Cerqueira
- REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
| | - Isabel Moura
- LAQV-REQUIMTE, Departamento de Química, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Marta S P Carepo
- LAQV-REQUIMTE, Departamento de Química, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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Different adaptive strategies in E. coli populations evolving under macronutrient limitation and metal ion limitation. BMC Evol Biol 2018; 18:72. [PMID: 29776341 PMCID: PMC5960147 DOI: 10.1186/s12862-018-1191-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 05/04/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Adaptive responses to nutrient limitation involve mutations that increase the efficiency of usage or uptake of the limiting nutrient. However, starvation of different nutrients has contrasting effects on physiology, resulting in different evolutionary responses. Most studies performed to understand these evolutionary responses have focused only on macronutrient limitation. Hence our understanding of adaptation under limitation of other forms of nutrients is limited. In this study, we compared the evolutionary response in populations evolving under growth-limiting conditions for a macronutrient and a major cation. RESULTS We evolved eight populations of E. coli in nutrient-limited chemostats for 400 generations to identify the genetic basis of the mechanisms involved in efficient usage of two nutrients: nitrogen and magnesium. Our population genomic sequencing work, based on this study and previous work, allowed us to identify targets of selection under these nutrient limiting conditions. Global transcriptional regulators glnGL were targets of selection under nitrogen starvation, while proteins involved in outer-membrane biogenesis (genes from the lpt operon) were targets of selection under magnesium starvation. The protein involved in cell-cycle arrest (yhaV) was a target of selection in both environments. We re-constructed specific mutants to analyze the effect of individual mutations on fitness in nutrient limiting conditions in chemostats and in batch cultures. We further demonstrated that adaptation to nitrogen starvation proceeds via a nutrient specific mechanism, while that to magnesium starvation involves a more general mechanism. CONCLUSIONS Our results show two different forms of adaptive strategies under limitation of nutrients that effect cellular physiology in different ways. Adaptation to nitrogen starvation proceeds by upregulation of transcriptional regulator glnG and subsequently of transporter protein amtB, both of which results in increased nitrogen scavenging ability of the cell. On the other hand, adaptation to magnesium starvation proceeds via the restructuring of the cell outer-membrane, allowing magnesium to be redistributed to other biological processes. Also, adaptation to the chemostat environment involves selection for loss of function mutations in genes that under nutrient-limiting conditions interfere with continuous growth.
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32
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Lurthy T, Alloisio N, Fournier P, Anchisi S, Ponsero A, Normand P, Pujic P, Boubakri H. Molecular response to nitrogen starvation by Frankia alni ACN14a revealed by transcriptomics and functional analysis with a fosmid library in Escherichia coli. Res Microbiol 2018; 169:90-100. [PMID: 29378337 DOI: 10.1016/j.resmic.2017.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 11/21/2017] [Accepted: 12/06/2017] [Indexed: 12/20/2022]
Abstract
The transcriptome of Frankia alni strain ACN14a was compared between in vitro ammonium-replete (N-replete) and ammonium-free dinitrogen-fixing (N-fixing) conditions using DNA arrays. A Welch-test (p < 0.05) revealed significant upregulation of 252 genes under N-fixing vs. N-replete (fold-change (FC) ≥ 2), as well as significant downregulation of 48 other genes (FC ≤ 0.5). Interestingly, there were 104 Frankia genes upregulated in vitro that were also significantly upregulated in symbiosis with Alnus glutinosa, while the other 148 genes were not, showing that the physiology of in vitro fixation is markedly different from that under symbiotic conditions. In particular,in vitro fixing cells were seen to upregulate genes identified as coding for a nitrite reductase, and amidases that were not upregulated in symbiosis. Confirmatory assays for nitrite reductase showed that Frankia indeed reduced nitrite and used it as a nitrogen source. An Escherichia coli fosmid clone carrying the nirB region was able to grow better in the presence of 5 mM nitrite than without it, confirming the function of the genome region. The physiological pattern that emerges shows that Frankia undergoes nitrogen starvation that induces a molecular response different from that seen in symbiosis.
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Affiliation(s)
- Tristan Lurthy
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Nicole Alloisio
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Pascale Fournier
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Stéphanie Anchisi
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Alise Ponsero
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Philippe Normand
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Petar Pujic
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Hasna Boubakri
- Université de Lyon, F-69622, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France.
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GlnK Facilitates the Dynamic Regulation of Bacterial Nitrogen Assimilation. Biophys J 2017; 112:2219-2230. [PMID: 28538158 PMCID: PMC5448240 DOI: 10.1016/j.bpj.2017.04.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 04/10/2017] [Accepted: 04/14/2017] [Indexed: 11/29/2022] Open
Abstract
Ammonium assimilation in Escherichia coli is regulated by two paralogous proteins (GlnB and GlnK), which orchestrate interactions with regulators of gene expression, transport proteins, and metabolic pathways. Yet how they conjointly modulate the activity of glutamine synthetase, the key enzyme for nitrogen assimilation, is poorly understood. We combine experiments and theory to study the dynamic roles of GlnB and GlnK during nitrogen starvation and upshift. We measure time-resolved in vivo concentrations of metabolites, total and posttranslationally modified proteins, and develop a concise biochemical model of GlnB and GlnK that incorporates competition for active and allosteric sites, as well as functional sequestration of GlnK. The model predicts the responses of glutamine synthetase, GlnB, and GlnK under time-varying external ammonium level in the wild-type and two genetic knock-outs. Our results show that GlnK is tightly regulated under nitrogen-rich conditions, yet it is expressed during ammonium run-out and starvation. This suggests a role for GlnK as a buffer of nitrogen shock after starvation, and provides a further functional link between nitrogen and carbon metabolisms.
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López MF, Cabrera JJ, Salas A, Delgado MJ, López-García SL. Dissecting the role of NtrC and RpoN in the expression of assimilatory nitrate and nitrite reductases in Bradyrhizobium diazoefficiens. Antonie Van Leeuwenhoek 2017; 110:531-542. [PMID: 28040856 DOI: 10.1007/s10482-016-0821-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 12/19/2016] [Indexed: 11/28/2022]
Abstract
Bradyrhizobium diazoefficiens, a nitrogen-fixing endosymbiont of soybeans, is a model strain for studying rhizobial denitrification. This bacterium can also use nitrate as the sole nitrogen (N) source during aerobic growth by inducing an assimilatory nitrate reductase encoded by nasC located within the narK-bjgb-flp-nasC operon along with a nitrite reductase encoded by nirA at a different chromosomal locus. The global nitrogen two-component regulatory system NtrBC has been reported to coordinate the expression of key enzymes in nitrogen metabolism in several bacteria. In this study, we demonstrate that disruption of ntrC caused a growth defect in B. diazoefficiens cells in the presence of nitrate or nitrite as the sole N source and a decreased activity of the nitrate and nitrite reductase enzymes. Furthermore, the expression of narK-lacZ or nirA-lacZ transcriptional fusions was significantly reduced in the ntrC mutant after incubation under nitrate assimilation conditions. A B. diazoefficiens rpoN 1/2 mutant, lacking both copies of the gene encoding the alternative sigma factor σ54, was also defective in aerobic growth with nitrate as the N source as well as in nitrate and nitrite reductase expression. These results demonstrate that the NtrC regulator is required for expression of the B. diazoefficiens nasC and nirA genes and that the sigma factor RpoN is also involved in this regulation.
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Affiliation(s)
- María F López
- Instituto de Biotecnología y Biología Molecular (IBBM), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, Calles 47 y 115, B1900AJL, La Plata, Argentina
| | - Juan J Cabrera
- Estación Experimental del Zaidín, CSIC, PO Box 419, 18080, Granada, Spain
| | - Ana Salas
- Estación Experimental del Zaidín, CSIC, PO Box 419, 18080, Granada, Spain
| | - María J Delgado
- Estación Experimental del Zaidín, CSIC, PO Box 419, 18080, Granada, Spain.
| | - Silvina L López-García
- Instituto de Biotecnología y Biología Molecular (IBBM), Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata y CCT La Plata-CONICET, Calles 47 y 115, B1900AJL, La Plata, Argentina.
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Adaptation to Potassium-Limitation Is Essential forAcinetobacter baumanniiPneumonia Pathogenesis. J Infect Dis 2016; 214:2006-2013. [DOI: 10.1093/infdis/jiw476] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 09/27/2016] [Indexed: 01/01/2023] Open
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Hartman CE, Samuels DJ, Karls AC. Modulating Salmonella Typhimurium's Response to a Changing Environment through Bacterial Enhancer-Binding Proteins and the RpoN Regulon. Front Mol Biosci 2016; 3:41. [PMID: 27583250 PMCID: PMC4987338 DOI: 10.3389/fmolb.2016.00041] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 07/28/2016] [Indexed: 12/25/2022] Open
Abstract
Transcription sigma factors direct the selective binding of RNA polymerase holoenzyme (Eσ) to specific promoters. Two families of sigma factors determine promoter specificity, the σ(70) (RpoD) family and the σ(54) (RpoN) family. In transcription controlled by σ(54), the Eσ(54)-promoter closed complex requires ATP hydrolysis by an associated bacterial enhancer-binding protein (bEBP) for the transition to open complex and transcription initiation. Given the wide host range of Salmonella enterica serovar Typhimurium, it is an excellent model system for investigating the roles of RpoN and its bEBPs in modulating the lifestyle of bacteria. The genome of S. Typhimurium encodes 13 known or predicted bEBPs, each responding to a unique intracellular or extracellular signal. While the regulons of most alternative sigma factors respond to a specific environmental or developmental signal, the RpoN regulon is very diverse, controlling genes for response to nitrogen limitation, nitric oxide stress, availability of alternative carbon sources, phage shock/envelope stress, toxic levels of zinc, nucleic acid damage, and other stressors. This review explores how bEBPs respond to environmental changes encountered by S. Typhimurium during transmission/infection and influence adaptation through control of transcription of different components of the S. Typhimurium RpoN regulon.
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Affiliation(s)
| | - David J Samuels
- Department of Microbiology, University of Georgia Athens, GA, USA
| | - Anna C Karls
- Department of Microbiology, University of Georgia Athens, GA, USA
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Abstract
The metabolite 2-oxoglutarate (also known as α-ketoglutarate, 2-ketoglutaric acid, or oxoglutaric acid) lies at the intersection between the carbon and nitrogen metabolic pathways. This compound is a key intermediate of one of the most fundamental biochemical pathways in carbon metabolism, the tricarboxylic acid (TCA) cycle. In addition, 2-oxoglutarate also acts as the major carbon skeleton for nitrogen-assimilatory reactions. Experimental data support the conclusion that intracellular levels of 2-oxoglutarate fluctuate according to nitrogen and carbon availability. This review summarizes how nature has capitalized on the ability of 2-oxoglutarate to reflect cellular nutritional status through evolution of a variety of 2-oxoglutarate-sensing regulatory proteins. The number of metabolic pathways known to be regulated by 2-oxoglutarate levels has increased significantly in recent years. The signaling properties of 2-oxoglutarate are highlighted by the fact that this metabolite regulates the synthesis of the well-established master signaling molecule, cyclic AMP (cAMP), in Escherichia coli.
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38
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Ceizel Borella G, Lagares A, Valverde C. Expression of the Sinorhizobium meliloti small RNA gene mmgR is controlled by the nitrogen source. FEMS Microbiol Lett 2016; 363:fnw069. [PMID: 27010014 DOI: 10.1093/femsle/fnw069] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/20/2016] [Indexed: 01/30/2023] Open
Abstract
Small non-coding regulatory RNAs (sRNAs) are key players in post-transcriptional regulation of gene expression. Hundreds of sRNAs have been identified in Sinorhizobium meliloti, but their biological function remains unknown for most of them. In this study, we characterized the expression pattern of the gene encoding the 77-nt sRNA MmgR in S. meliloti strain 2011. A chromosomal transcriptional reporter fusion (PmmgR-gfp) showed that the mmgR promoter is active along different stages of the interaction with alfalfa roots. In pure cultures, PmmgR-gfp activity paralleled the sRNA abundance indicating that mmgR expression is primarily controlled at the level of transcriptional initiation. PmmgR-gfp activity was higher during growth in rhizobial defined medium (RDM) than in TY medium. Furthermore, PmmgR-gfp was induced at 60 min after shifting growing cells from TY to RDM medium, i.e. shorter than the cell doubling time. In defined RDM medium containing NO3 (-), both PmmgR-gfp and MmgR level were repressed by the addition of tryptone or single amino acids, suggesting that mmgR expression depends on the cellular nitrogen (N) status. In silico analysis failed to detect conserved motifs upstream the promoter RNA polymerase binding site, but revealed a strongly conserved motif centered at -28 that may be linked to the observed regulatory pattern by the N source.
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Affiliation(s)
- Germán Ceizel Borella
- Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina
| | - Antonio Lagares
- Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina
| | - Claudio Valverde
- Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Roque Sáenz Peña 352, Bernal B1876BXD, Buenos Aires, Argentina
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39
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Oliveira MAS, Gerhardt ECM, Huergo LF, Souza EM, Pedrosa FO, Chubatsu LS. 2-Oxoglutarate levels control adenosine nucleotide binding by Herbaspirillum seropedicae PII proteins. FEBS J 2015; 282:4797-809. [PMID: 26433003 DOI: 10.1111/febs.13542] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 09/22/2015] [Accepted: 09/29/2015] [Indexed: 11/29/2022]
Abstract
Nitrogen metabolism in Proteobacteria is controlled by the Ntr system, in which PII proteins play a pivotal role, controlling the activity of target proteins in response to the metabolic state of the cell. Characterization of the binding of molecular effectors to these proteins can provide information about their regulation. Here, the binding of ATP, ADP and 2-oxoglutarate (2-OG) to the Herbaspirillum seropedicae PII proteins, GlnB and GlnK, was characterized using isothermal titration calorimetry. Results show that these proteins can bind three molecules of ATP, ADP and 2-OG with homotropic negative cooperativity, and 2-OG binding stabilizes the binding of ATP. Results also show that the affinity of uridylylated forms of GlnB and GlnK for nucleotides is significantly lower than that of the nonuridylylated proteins. Furthermore, fluctuations in the intracellular concentration of 2-OG in response to nitrogen availability are shown. Results suggest that under nitrogen-limiting conditions, PII proteins tend to bind ATP and 2-OG. By contrast, after an ammonium shock, a decrease in the 2-OG concentration is observed causing a decrease in the affinity of PII proteins for ATP. This phenomenon may facilitate the exchange of ATP for ADP on the ligand-binding pocket of PII proteins, thus it is likely that under low ammonium, low 2-OG levels would favor the ADP-bound state.
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Affiliation(s)
- Marco A S Oliveira
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
| | - Edileusa C M Gerhardt
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
| | - Luciano F Huergo
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
| | - Emanuel M Souza
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
| | - Fábio O Pedrosa
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
| | - Leda S Chubatsu
- Department of Biochemistry and Molecular Biology, Universidade Federal do Parana, Curitiba, Brazil
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40
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Lüttmann D, Göpel Y, Görke B. Cross-Talk between the Canonical and the Nitrogen-Related Phosphotransferase Systems Modulates Synthesis of the KdpFABC Potassium Transporter in Escherichia coli. J Mol Microbiol Biotechnol 2015; 25:168-77. [DOI: 10.1159/000375497] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Many Proteobacteria possess the regulatory nitrogen-related phosphotransferase system (PTS<sup>Ntr</sup>), which operates in parallel to the transport PTS. PTS<sup>Ntr</sup> is composed of the proteins EI<sup>Ntr</sup> and NPr and the final phosphate acceptor EIIA<sup>Ntr</sup>. Both PTSs can exchange phosphoryl groups among each other. Proteins governing K<sup>+</sup> uptake represent a major target of PTS<sup>Ntr</sup> in <i>Escherichia coli</i>. Nonphosphorylated EIIA<sup>Ntr</sup> binds and stimulates the K<sup>+</sup> sensor KdpD, which activates expression of the <i>kdpFABC</i> operon encoding a K<sup>+</sup> transporter. Here we show that this regulation also operates in an <i>ilvG</i><sup><i>+</i></sup> strain ruling out previous concern about interference with a nonfunctional <i>ilvG</i> allele present in many strains. Furthermore, we analyzed phosphorylation of EIIA<sup>Ntr</sup>. In wild-type cells EIIA<sup>Ntr</sup> is predominantly phosphorylated, regardless of the growth stage and the utilized carbon source. However, cross-phosphorylation of EIIA<sup>Ntr</sup> by the transport PTS becomes apparent in the absence of EI<sup>Ntr</sup>: EIIA<sup>Ntr</sup> is predominantly nonphosphorylated when cells grow on a PTS sugar and phosphorylated when a non-PTS carbohydrate is utilized. These differences in phosphorylation are transduced into corresponding <i>kdpFABC</i> transcription levels. Thus, the transport PTS may affect phosphorylation of EIIA<sup>Ntr</sup> and accordingly modulate processes controlled by EIIA<sup>Ntr</sup>. Our data suggest that this cross-talk becomes most relevant under conditions that would inhibit activity of EI<sup>Ntr</sup>.
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41
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Gerhardt EC, Rodrigues TE, Müller-Santos M, Pedrosa FO, Souza EM, Forchhammer K, Huergo LF. The Bacterial signal transduction protein GlnB regulates the committed step in fatty acid biosynthesis by acting as a dissociable regulatory subunit of acetyl-CoA carboxylase. Mol Microbiol 2015; 95:1025-35. [DOI: 10.1111/mmi.12912] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2014] [Indexed: 11/30/2022]
Affiliation(s)
- Edileusa C.M. Gerhardt
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular; Universidade Federal do Paraná; CEP 81531-990 CP 19046 Curitiba PR Brazil
- Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls Universität Tübingen; Auf der Morgenstelle 28 Tübingen 72076 Germany
| | - Thiago E. Rodrigues
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular; Universidade Federal do Paraná; CEP 81531-990 CP 19046 Curitiba PR Brazil
| | - Marcelo Müller-Santos
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular; Universidade Federal do Paraná; CEP 81531-990 CP 19046 Curitiba PR Brazil
| | - Fabio O. Pedrosa
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular; Universidade Federal do Paraná; CEP 81531-990 CP 19046 Curitiba PR Brazil
| | - Emanuel M. Souza
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular; Universidade Federal do Paraná; CEP 81531-990 CP 19046 Curitiba PR Brazil
| | - Karl Forchhammer
- Interfakultäres Institut für Mikrobiologie und Infektionsmedizin der Eberhard-Karls Universität Tübingen; Auf der Morgenstelle 28 Tübingen 72076 Germany
| | - Luciano F. Huergo
- Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Departamento de Bioquímica e Biologia Molecular; Universidade Federal do Paraná; CEP 81531-990 CP 19046 Curitiba PR Brazil
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42
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Alteri CJ, Himpsl SD, Mobley HLT. Preferential use of central metabolism in vivo reveals a nutritional basis for polymicrobial infection. PLoS Pathog 2015; 11:e1004601. [PMID: 25568946 PMCID: PMC4287612 DOI: 10.1371/journal.ppat.1004601] [Citation(s) in RCA: 76] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 12/04/2014] [Indexed: 12/04/2022] Open
Abstract
The human genitourinary tract is a common anatomical niche for polymicrobial infection and a leading site for the development of bacteremia and sepsis. Most uncomplicated, community-acquired urinary tract infections (UTI) are caused by Escherichia coli, while another bacterium, Proteus mirabilis, is more often associated with complicated UTI. Here, we report that uropathogenic E. coli and P. mirabilis have divergent requirements for specific central pathways in vivo despite colonizing and occupying the same host environment. Using mutants of specific central metabolism enzymes, we determined glycolysis mutants lacking pgi, tpiA, pfkA, or pykA all have fitness defects in vivo for P. mirabilis but do not affect colonization of E. coli during UTI. Similarly, the oxidative pentose phosphate pathway is required only for P. mirabilis in vivo. In contrast, gluconeogenesis is required only for E. coli fitness in vivo. The remarkable difference in central pathway utilization between E. coli and P. mirabilis during experimental UTI was also observed for TCA cycle mutants in sdhB, fumC, and frdA. The distinct in vivo requirements between these pathogens suggest E. coli and P. mirabilis are not direct competitors within host urinary tract nutritional niche. In support of this, we found that co-infection with E. coli and P. mirabilis wild-type strains enhanced bacterial colonization and persistence of both pathogens during UTI. Our results reveal that complementary utilization of central carbon metabolism facilitates polymicrobial disease and suggests microbial activity in vivo alters the host urinary tract nutritional niche. The human urinary tract is a leading source for polymicrobial infections and for the development of bacteremia and sepsis. Treating these potentially dangerous infections have recently become more challenging due to the appearance of uropathogenic strains that are resistant to the many of the most commonly prescribed antibiotics. The majority of urinary tract infections (UTI) are caused by Escherichia coli, while another bacterium, Proteus mirabilis, is more likely to cause catheter-associated UTI. Here, we report that uropathogenic E. coli and P. mirabilis have divergent nutritional requirements despite growing in the same host environment. This result indicates that E. coli and P. mirabilis do not directly compete for nutrients during UTI. Indeed, we found that persistence of both pathogens is enhanced when they co-colonize the host. This work represents an important step toward understanding the basic nutritional requirements for two major pathogens that cause UTI and shows how mixed infections can change these requirements. Understanding how bacteria grow during infections is fundamental to ultimately uncover new ways to combat increasingly drug-resistant bacterial infections.
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Affiliation(s)
- Christopher J. Alteri
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Stephanie D. Himpsl
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Harry L. T. Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail:
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43
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Transcriptional profiles of Haloferax mediterranei based on nitrogen availability. J Biotechnol 2014; 193:100-7. [PMID: 25435380 DOI: 10.1016/j.jbiotec.2014.11.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Revised: 11/07/2014] [Accepted: 11/19/2014] [Indexed: 11/23/2022]
Abstract
The haloarchaeon Haloferax mediterranei is able to grow in the presence of different inorganic and organic nitrogen sources by means of the assimilatory pathway under aerobic conditions. In order to identify genes of potential importance in nitrogen metabolism and its regulation in the halophilic microorganism, we have analysed its global gene expression in three culture media with different nitrogen sources: (a) cells were grown stationary and exponentially in ammonium, (b) cells were grown exponentially in nitrate, and (c) cells were shifted to nitrogen starvation conditions. The main differences in the transcriptional profiles have been identified between the cultures with ammonium as nitrogen source and the cultures with nitrate or nitrogen starvation, supporting previous results which indicate the absence of ammonium as the factor responsible for the expression of genes involved in nitrate assimilation pathway. The results have also permitted the identification of transcriptional regulators and changes in metabolic pathways related to the catabolism and anabolism of amino acids or nucleotides. The microarray data was validated by real-time quantitative PCR on 4 selected genes involved in nitrogen metabolism. This work represents the first transcriptional profiles study related to nitrogen assimilation metabolism in extreme halophilic microorganisms using microarray technology.
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44
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Valentini M, García-Mauriño SM, Pérez-Martínez I, Santero E, Canosa I, Lapouge K. Hierarchical management of carbon sources is regulated similarly by the CbrA/B systems in Pseudomonas aeruginosa and Pseudomonas putida. MICROBIOLOGY-SGM 2014; 160:2243-2252. [PMID: 25031426 DOI: 10.1099/mic.0.078873-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The CbrA/B system in pseudomonads is involved in the utilization of carbon sources and carbon catabolite repression (CCR) through the activation of the small RNAs crcZ in Pseudomonas aeruginosa, and crcZ and crcY in Pseudomonas putida. Interestingly, previous works reported that the CbrA/B system activity in P. aeruginosa PAO1 and P. putida KT2442 responded differently to the presence of different carbon sources, thus raising the question of the exact nature of the signal(s) detected by CbrA. Here, we demonstrated that the CbrA/B/CrcZ(Y) signal transduction pathway is similarly activated in the two Pseudomonas species. We show that the CbrA sensor kinase is fully interchangeable between the two species and, moreover, responds similarly to the presence of different carbon sources. In addition, a metabolomics analysis supported the hypothesis that CCR responds to the internal energy status of the cell, as the internal carbon/nitrogen ratio seems to determine CCR and non-CCR conditions. The strong difference found in the 2-oxoglutarate/glutamine ratio between CCR and non-CCR conditions points to the close relationship between carbon and nitrogen availability, or the relationship between the CbrA/B and NtrB/C systems, suggesting that both regulatory systems sense the same sort or interrelated signal.
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Affiliation(s)
- Martina Valentini
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
| | - Sofía M García-Mauriño
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Isabel Pérez-Martínez
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Eduardo Santero
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Inés Canosa
- Centro Andaluz de Biología del Desarollo/CSIC/Universidad Pablo de Olavide, 41013 Seville, Spain
| | - Karine Lapouge
- Department of Fundamental Microbiology, University of Lausanne, 1015 Lausanne, Switzerland
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45
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Brown DR, Barton G, Pan Z, Buck M, Wigneshweraraj S. Nitrogen stress response and stringent response are coupled in Escherichia coli. Nat Commun 2014; 5:4115. [PMID: 24947454 PMCID: PMC4066584 DOI: 10.1038/ncomms5115] [Citation(s) in RCA: 121] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 05/13/2014] [Indexed: 01/10/2023] Open
Abstract
Assimilation of nitrogen is an essential process in bacteria. The nitrogen regulation stress response is an adaptive mechanism used by nitrogen-starved Escherichia coli to scavenge for alternative nitrogen sources and requires the global transcriptional regulator NtrC. In addition, nitrogen-starved E. coli cells synthesize a signal molecule, guanosine tetraphosphate (ppGpp), which serves as an effector molecule of many processes including transcription to initiate global physiological changes, collectively termed the stringent response. The regulatory mechanisms leading to elevated ppGpp levels during nutritional stresses remain elusive. Here, we show that transcription of relA, a key gene responsible for the synthesis of ppGpp, is activated by NtrC during nitrogen starvation. The results reveal that NtrC couples these two major bacterial stress responses to manage conditions of nitrogen limitation, and provide novel mechanistic insights into how a specific nutritional stress leads to elevating ppGpp levels in bacteria.
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Affiliation(s)
- Daniel R. Brown
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, UK
| | - Geraint Barton
- Centre for Systems Biology and Bioinformatics, Division of Biosciences, Imperial College London, London SW7 2AZ, UK
| | - Zhensheng Pan
- MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London SW7 2AZ, UK
| | - Martin Buck
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
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46
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Abstract
Beyond fuelling cellular activities with building blocks and energy, metabolism also integrates environmental conditions into intracellular signals. The underlying regulatory network is complex and multifaceted: it ranges from slow interactions, such as changing gene expression, to rapid ones, such as the modulation of protein activity via post-translational modification or the allosteric binding of small molecules. In this Review, we outline the coordination of common metabolic tasks, including nutrient uptake, central metabolism, the generation of energy, the supply of amino acids and protein synthesis. Increasingly, a set of key metabolites is recognized to control individual regulatory circuits, which carry out specific functions of information input and regulatory output. Such a modular view of microbial metabolism facilitates an intuitive understanding of the molecular mechanisms that underlie cellular decision making.
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47
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Zurauskienė J, Kirk P, Thorne T, Pinney J, Stumpf M. Derivative processes for modelling metabolic fluxes. ACTA ACUST UNITED AC 2014; 30:1892-8. [PMID: 24578401 PMCID: PMC4071196 DOI: 10.1093/bioinformatics/btu069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Motivation: One of the challenging questions in modelling biological systems is to characterize the functional forms of the processes that control and orchestrate molecular and cellular phenotypes. Recently proposed methods for the analysis of metabolic pathways, for example, dynamic flux estimation, can only provide estimates of the underlying fluxes at discrete time points but fail to capture the complete temporal behaviour. To describe the dynamic variation of the fluxes, we additionally require the assumption of specific functional forms that can capture the temporal behaviour. However, it also remains unclear how to address the noise which might be present in experimentally measured metabolite concentrations. Results: Here we propose a novel approach to modelling metabolic fluxes: derivative processes that are based on multiple-output Gaussian processes (MGPs), which are a flexible non-parametric Bayesian modelling technique. The main advantages that follow from MGPs approach include the natural non-parametric representation of the fluxes and ability to impute the missing data in between the measurements. Our derivative process approach allows us to model changes in metabolite derivative concentrations and to characterize the temporal behaviour of metabolic fluxes from time course data. Because the derivative of a Gaussian process is itself a Gaussian process, we can readily link metabolite concentrations to metabolic fluxes and vice versa. Here we discuss how this can be implemented in an MGP framework and illustrate its application to simple models, including nitrogen metabolism in Escherichia coli. Availability and implementation: R code is available from the authors upon request. Contact:j.norkunaite@imperial.ac.uk; m.stumpf@imperial.ac.uk Supplementary information:Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Justina Zurauskienė
- Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Paul Kirk
- Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Thomas Thorne
- Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - John Pinney
- Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Michael Stumpf
- Theoretical Systems Biology Group, Centre for Bioinformatics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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48
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Schumacher J, Waite CJ, Bennett MH, Perez MF, Shethi K, Buck M. Differential secretome analysis of Pseudomonas syringae pv tomato using gel-free MS proteomics. FRONTIERS IN PLANT SCIENCE 2014; 5:242. [PMID: 25071788 PMCID: PMC4082315 DOI: 10.3389/fpls.2014.00242] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 05/12/2014] [Indexed: 05/03/2023]
Abstract
The plant pathogen Pseudomonas syringae pv.tomato (DC3000) causes virulence by delivering effector proteins into host plant cells through its type three secretion system (T3SS). In response to the plant environment DC3000 expresses hypersensitive response and pathogenicity genes (hrp). Pathogenesis depends on the ability of the pathogen to manipulate the plant metabolism and to inhibit plant immunity, which depends to a large degree on the plant's capacity to recognize both pathogen and microbial determinants (PAMP/MAMP-triggered immunity). We have developed and employed MS-based shotgun and targeted proteomics to (i) elucidate the extracellular and secretome composition of DC3000 and (ii) evaluate temporal features of the assembly of the T3SS and the secretion process together with its dependence of pH. The proteomic screen, under hrp inducing in vitro conditions, of extracellular and cytoplasmatic fractions indicated the segregated presence of not only T3SS implicated proteins such as HopP1, HrpK1, HrpA1 and AvrPto1, but also of proteins not usually associated with the T3SS or with pathogenicity. Using multiple reaction monitoring MS (MRM-MS) to quantify HrpA1 and AvrPto1, we found that HrpA1 is rapidly expressed, at a strict pH-dependent rate and is post-translationally processed extracellularly. These features appear to not interfere with rapid AvrPto1 expression and secretion but may suggest some temporal post-translational regulatory mechanism of the T3SS assembly. The high specificity and sensitivity of the MRM-MS approach should provide a powerful tool to measure secretion and translocation in infected tissues.
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Affiliation(s)
- Jörg Schumacher
- *Correspondence: Jörg Schumacher and Martin Buck, Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, London, SW7 2AZ, UK e-mail: ;
| | | | | | | | | | - Martin Buck
- *Correspondence: Jörg Schumacher and Martin Buck, Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, London, SW7 2AZ, UK e-mail: ;
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49
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Behrends V, Maharjan RP, Ryall B, Feng L, Liu B, Wang L, Bundy JG, Ferenci T. A metabolic trade-off between phosphate and glucose utilization in Escherichia coli. ACTA ACUST UNITED AC 2014; 10:2820-2. [DOI: 10.1039/c4mb00313f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using full genome sequencing and metabolomics we show that adaptation to chronic nutrient starvation reduces metabolic flexibility inEscherichia coli.
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Affiliation(s)
- Volker Behrends
- Department of Surgery and Cancer
- Imperial College London
- London SW7 2AZ, UK
| | - Ram P. Maharjan
- School of Molecular Bioscience
- University of Sydney
- , Australia
| | - Ben Ryall
- School of Molecular Bioscience
- University of Sydney
- , Australia
| | - Lu Feng
- TEDA Institute of Biological Sciences and Biotechnology
- Nankai University
- Tianjin 300457, P. R. China
- Key Laboratory of Molecular Microbiology and Technology
- Ministry of Education
| | - Bin Liu
- TEDA Institute of Biological Sciences and Biotechnology
- Nankai University
- Tianjin 300457, P. R. China
- Key Laboratory of Molecular Microbiology and Technology
- Ministry of Education
| | - Lei Wang
- TEDA Institute of Biological Sciences and Biotechnology
- Nankai University
- Tianjin 300457, P. R. China
- Key Laboratory of Molecular Microbiology and Technology
- Ministry of Education
| | - Jacob G. Bundy
- Department of Surgery and Cancer
- Imperial College London
- London SW7 2AZ, UK
| | - Thomas Ferenci
- School of Molecular Bioscience
- University of Sydney
- , Australia
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