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Gutiérrez-García K, Whitaker MRL, Bustos-Díaz ED, Salzman S, Ramos-Aboites HE, Reitz ZL, Pierce NE, Cibrián-Jaramillo A, Barona-Gómez F. Gut microbiomes of cycad-feeding insects tolerant to β-methylamino-L-alanine (BMAA) are rich in siderophore biosynthesis. ISME COMMUNICATIONS 2023; 3:122. [PMID: 37993724 PMCID: PMC10665472 DOI: 10.1038/s43705-023-00323-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 10/17/2023] [Accepted: 10/25/2023] [Indexed: 11/24/2023]
Abstract
Ingestion of the cycad toxins β-methylamino-L-alanine (BMAA) and azoxyglycosides is harmful to diverse organisms. However, some insects are specialized to feed on toxin-rich cycads with apparent immunity. Some cycad-feeding insects possess a common set of gut bacteria, which might play a role in detoxifying cycad toxins. Here, we investigated the composition of gut microbiota from a worldwide sample of cycadivorous insects and characterized the biosynthetic potential of selected bacteria. Cycadivorous insects shared a core gut microbiome consisting of six bacterial taxa, mainly belonging to the Proteobacteria, which we were able to isolate. To further investigate selected taxa from diverging lineages, we performed shotgun metagenomic sequencing of co-cultured bacterial sub-communities. We characterized the biosynthetic potential of four bacteria from Serratia, Pantoea, and two different Stenotrophomonas lineages, and discovered a suite of biosynthetic gene clusters notably rich in siderophores. Siderophore semi-untargeted metabolomics revealed a broad range of chemically related yet diverse iron-chelating metabolites, including desferrioxamine B, suggesting the occurrence of an unprecedented desferrioxamine-like biosynthetic pathway that remains to be identified. These results provide a foundation for future investigations into how cycadivorous insects tolerate diets rich in azoxyglycosides, BMAA, and other cycad toxins, including a possible role for bacterial siderophores.
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Affiliation(s)
- Karina Gutiérrez-García
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Km 9.6 Libramiento Irapuato - León, Irapuato, Guanajuato, 36824, México
- Department of Embryology, Carnegie Institution for Science, 3520 San Martin Drive, Baltimore, MD, 21218, USA
| | - Melissa R L Whitaker
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
- Department of Biological Sciences, East Tennessee State University, Johnson City, TN, 37614, USA.
| | - Edder D Bustos-Díaz
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Km 9.6 Libramiento Irapuato - León, Irapuato, Guanajuato, 36824, México
- Institute of Biology, Leiden University, Sylviusweg 72, Leiden, 2333 BE, The Netherlands
| | - Shayla Salzman
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
- University of Georgia, Entomology Department, Athens, GA, 30602, USA
| | - Hilda E Ramos-Aboites
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Km 9.6 Libramiento Irapuato - León, Irapuato, Guanajuato, 36824, México
| | - Zachary L Reitz
- Bioinformatics Group, Wageningen University, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Naomi E Pierce
- Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Angélica Cibrián-Jaramillo
- Ecological and Evolutionary Genomics Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Km 9.6 Libramiento Irapuato - León, Irapuato, Guanajuato, 36824, México
- Naturalis Biodiversity Center, Darwinweg 2, 2333 CR, Leiden, The Netherlands
| | - Francisco Barona-Gómez
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav-IPN, Km 9.6 Libramiento Irapuato - León, Irapuato, Guanajuato, 36824, México.
- Institute of Biology, Leiden University, Sylviusweg 72, Leiden, 2333 BE, The Netherlands.
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Golanowska M, Potrykus M, Motyka-Pomagruk A, Kabza M, Bacci G, Galardini M, Bazzicalupo M, Makalowska I, Smalla K, Mengoni A, Hugouvieux-Cotte-Pattat N, Lojkowska E. Comparison of Highly and Weakly Virulent Dickeya solani Strains, With a View on the Pangenome and Panregulon of This Species. Front Microbiol 2018; 9:1940. [PMID: 30233505 PMCID: PMC6127512 DOI: 10.3389/fmicb.2018.01940] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 07/31/2018] [Indexed: 11/30/2022] Open
Abstract
Bacteria belonging to the genera Dickeya and Pectobacterium are responsible for significant economic losses in a wide variety of crops and ornamentals. During last years, increasing losses in potato production have been attributed to the appearance of Dickeya solani. The D. solani strains investigated so far share genetic homogeneity, although different virulence levels were observed among strains of various origins. The purpose of this study was to investigate the genetic traits possibly related to the diverse virulence levels by means of comparative genomics. First, we developed a new genome assembly pipeline which allowed us to complete the D. solani genomes. Four de novo sequenced and ten publicly available genomes were used to identify the structure of the D. solani pangenome, in which 74.8 and 25.2% of genes were grouped into the core and dispensable genome, respectively. For D. solani panregulon analysis, we performed a binding site prediction for four transcription factors, namely CRP, KdgR, PecS and Fur, to detect the regulons of these virulence regulators. Most of the D. solani potential virulence factors were predicted to belong to the accessory regulons of CRP, KdgR, and PecS. Thus, some differences in gene expression could exist between D. solani strains. The comparison between a highly and a low virulent strain, IFB0099 and IFB0223, respectively, disclosed only small differences between their genomes but significant differences in the production of virulence factors like pectinases, cellulases and proteases, and in their mobility. The D. solani strains also diverge in the number and size of prophages present in their genomes. Another relevant difference is the disruption of the adhesin gene fhaB2 in the highly virulent strain. Strain IFB0223, which has a complete adhesin gene, is less mobile and less aggressive than IFB0099. This suggests that in this case, mobility rather than adherence is needed in order to trigger disease symptoms. This study highlights the utility of comparative genomics in predicting D. solani traits involved in the aggressiveness of this emerging plant pathogen.
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Affiliation(s)
- Malgorzata Golanowska
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Marta Potrykus
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Agata Motyka-Pomagruk
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Michal Kabza
- Department of Integrative Genomics, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland
| | - Giovanni Bacci
- Department of Biology, University of Florence, Florence, Italy
| | - Marco Galardini
- EMBL, EBI, Wellcome Trust Genome Campus, Cambridge, United Kingdom
| | | | - Izabela Makalowska
- Department of Integrative Genomics, Faculty of Biology, Adam Mickiewicz University, Poznan, Poland
| | - Kornelia Smalla
- Department of Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut - Federal Research Centre for Cultivated Plants, Braunschweig, Germany
| | - Alessio Mengoni
- Department of Biology, University of Florence, Florence, Italy
| | - Nicole Hugouvieux-Cotte-Pattat
- UMR5240 Microbiologie Adaptation et Pathogénie, Univ Lyon, CNRS, Univ Claude Bernard Lyon 1, INSA Lyon, Villeurbanne, France
| | - Ewa Lojkowska
- Department of Biotechnology, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
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Tanui CK, Shyntum DY, Priem SL, Theron J, Moleleki LN. Influence of the ferric uptake regulator (Fur) protein on pathogenicity in Pectobacterium carotovorum subsp. brasiliense. PLoS One 2017; 12:e0177647. [PMID: 28545065 PMCID: PMC5435245 DOI: 10.1371/journal.pone.0177647] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 04/30/2017] [Indexed: 11/19/2022] Open
Abstract
Iron is an important nutrient for the survival and growth of many organisms. In order to survive, iron uptake from the environment must be strictly regulated and maintained to avoid iron toxicity. The ferric uptake regulator protein (Fur) regulates genes involved in iron homeostasis in many bacteria, including phytopathogens. However, to date, the role played by Fur in the biology of Pectobacterium carotovorum subsp. brasiliense (Pcb1692), an important pathogen of potatoes, has not yet been studied. To this end, we used the lambda recombineering method to generate a fur mutant strain of Pcb1692 and assessed the virulence and fitness of the mutant strain. The results showed that production of siderophores in Pcb1692Δfur increased compared to the Pcb1692 wild-type and the complemented strain Pcb1692Δfur-pfur. However, production of N-acyl homoserine lactone (AHLs), biofilm formation, exopolysaccharide (EPS) production, virulence on potato tubers and swimming motility, were all significantly decreased in Pcb1692Δfur compared to the wild-type and complemented Pcb1692Δfur-pfur strains. The Pcb1692Δfur mutant also demonstrated significant sensitivity to oxidative stress when exposed to H2O2. Consistent with phenotypic results, qRT-PCR results demonstrated that Fur down-regulates genes which encode proteins associated with: iron uptake (HasA-extracellular heme-binding protein and Ferrodoxin-AED-0004132), stress response (SodC-superoxide dismutase), plant cell wall degrading enzymes (PrtA and CelV) and motility (FlhC and MotA). We conclude that the ferric uptake regulator protein (Fur) of Pcb1692 regulates traits that are important to host-pathogens interactions.
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Affiliation(s)
- Collins Kipngetich Tanui
- Forestry, Agriculture and Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Divine Yutefar Shyntum
- Forestry, Agriculture and Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Stefan Louis Priem
- Forestry, Agriculture and Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Jacques Theron
- Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, South Africa
| | - Lucy Novungayo Moleleki
- Forestry, Agriculture and Biotechnology Institute, University of Pretoria, Pretoria, South Africa
- Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, South Africa
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Identification and characterization of Cronobacter iron acquisition systems. Appl Environ Microbiol 2012; 78:6035-50. [PMID: 22706064 DOI: 10.1128/aem.01457-12] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Cronobacter spp. are emerging pathogens that cause severe infantile meningitis, septicemia, or necrotizing enterocolitis. Contaminated powdered infant formula has been implicated as the source of Cronobacter spp. in most cases, but questions still remain regarding the natural habitat and virulence potential for each strain. The iron acquisition systems in 231 Cronobacter strains isolated from different sources were identified and characterized. All Cronobacter spp. have both the Feo and Efe systems for acquisition of ferrous iron, and all plasmid-harboring strains (98%) have the aerobactin-like siderophore, cronobactin, for transport of ferric iron. All Cronobacter spp. have the genes encoding an enterobactin-like siderophore, although it was not functional under the conditions tested. Furthermore, all Cronobacter spp. have genes encoding five receptors for heterologous siderophores. A ferric dicitrate transport system (fec system) is encoded specifically by a subset of Cronobacter sakazakii and C. malonaticus strains, of which a high percentage were isolated from clinical samples. Phylogenetic analysis confirmed that the fec system is most closely related to orthologous genes present in human-pathogenic bacterial strains. Moreover, all strains of C. dublinensis and C. muytjensii encode two receptors, FcuA and Fct, for heterologous siderophores produced by plant pathogens. Identification of putative Fur boxes and expression of the genes under iron-depleted conditions revealed which genes and operons are components of the Fur regulon. Taken together, these results support the proposition that C. sakazakii and C. malonaticus may be more associated with the human host and C. dublinensis and C. muytjensii with plants.
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Mirus O, Strauss S, Nicolaisen K, von Haeseler A, Schleiff E. TonB-dependent transporters and their occurrence in cyanobacteria. BMC Biol 2009; 7:68. [PMID: 19821963 PMCID: PMC2771747 DOI: 10.1186/1741-7007-7-68] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 10/12/2009] [Indexed: 12/22/2022] Open
Abstract
Background Different iron transport systems evolved in Gram-negative bacteria during evolution. Most of the transport systems depend on outer membrane localized TonB-dependent transporters (TBDTs), a periplasma-facing TonB protein and a plasma membrane localized machinery (ExbBD). So far, iron chelators (siderophores), oligosaccharides and polypeptides have been identified as substrates of TBDTs. For iron transport, three uptake systems are defined: the lactoferrin/transferrin binding proteins, the porphyrin-dependent transporters and the siderophore-dependent transporters. However, for cyanobacteria almost nothing is known about possible TonB-dependent uptake systems for iron or other substrates. Results We have screened all publicly available eubacterial genomes for sequences representing (putative) TBDTs. Based on sequence similarity, we identified 195 clusters, where elements of one cluster may possibly recognize similar substrates. For Anabaena sp. PCC 7120 we identified 22 genes as putative TBDTs covering almost all known TBDT subclasses. This is a high number of TBDTs compared to other cyanobacteria. The expression of the 22 putative TBDTs individually depends on the presence of iron, copper or nitrogen. Conclusion We exemplified on TBDTs the power of CLANS-based classification, which demonstrates its importance for future application in systems biology. In addition, the tentative substrate assignment based on characterized proteins will stimulate the research of TBDTs in different species. For cyanobacteria, the atypical dependence of TBDT gene expression on different nutrition points to a yet unknown regulatory mechanism. In addition, we were able to clarify a hypothesis of the absence of TonB in cyanobacteria by the identification of according sequences.
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Affiliation(s)
- Oliver Mirus
- JWGU Frankfurt am Main, Cluster of Excellence Macromolecular Complexes, Centre of Membrane Proteomics, Department of Biosciences, Max-von-Laue Str. 9, 60438 Frankfurt, Germany.
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Tomisić V, Blanc S, Elhabiri M, Expert D, Albrecht-Gary AM. Iron(III) uptake and release by chrysobactin, a siderophore of the phytophatogenic bacterium Erwinia chrysanthemi. Inorg Chem 2008; 47:9419-30. [PMID: 18803373 DOI: 10.1021/ic801143e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The plant pathogenic enterobacterium Erwinia chrysanthemi causes important soft-rot disease on a wide range of plants including vegetables and ornamentals of economic importance. It produces a major mono(catecholate) siderophore, chrysobactin (alpha-N-(2,3-dihydroxybenzoyl)-D-lysyl-L-serine). To unravel the role of chrysobactin in the virulence of E. chrysanthemi, its iron(III) coordination properties were thus investigated in aqueous solutions using electrospray ionization mass spectrometric, potentiometric, and spectrophotometric methods. Moreover, kinetic experiments allowed us to determine the uptake and release mechanisms. The formation mechanism of the 1:1 complex reveals a key role of the terminal carboxylic group of chrysobactin in the binding of either FeOH(2+) or Fe2(OH)2(4+). The proton-driven dissociation of the ferric tris-, bis-, and mono(chrysobactin) complexes was also studied. For these three ferric complexes, a single protonation triggers the release of the bound chrysobactin molecule. Interestingly, the dissociation of the last ligand proceeded via the formation of an intermediate for which a salicylate-type mode of bonding was proposed.
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Affiliation(s)
- Vladislav Tomisić
- Laboratoire de Physico-Chimie Bioinorganique, ULP-CNRS (UMR 7177), Institut de Chimie, ECPM, 25 rue Becquerel, 67200 Strasbourg, France
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7
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Franza T, Mahé B, Expert D. Erwinia chrysanthemi requires a second iron transport route dependent of the siderophore achromobactin for extracellular growth and plant infection. Mol Microbiol 2005; 55:261-75. [PMID: 15612933 DOI: 10.1111/j.1365-2958.2004.04383.x] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Full virulence of the pectinolytic enterobacterium Erwinia chrysanthemi strain 3937 depends on the production in planta of the catechol-type siderophore chrysobactin. Under iron-limited conditions, E. chrysanthemi synthesizes a second siderophore called achromobactin belonging to the hydroxy/carboxylate class of siderophore. In this study, we cloned and functionally characterized a 13 kb long operon comprising seven genes required for the biosynthesis (acs) and extracellular release (yhcA) of achromobactin, as well as the gene encoding the specific outer membrane receptor for its ferric complex (acr). The promoter of this operon was negatively regulated by iron. In a fur null mutant, transcriptional fusions to the acsD and acsA genes were constitutively expressed. Band shift assays showed that the purified E. chrysanthemi Fur repressor protein specifically binds in vitro to the promoter region of the acsF gene confirming that the metalloregulation of the achromobactin operon is achieved directly by Fur. The temporal production of achromobactin in iron-depleted bacterial cultures was determined: achromobactin is produced before chrysobactin and its production decreases as that of chrysobactin increases. Pathogenicity tests performed on African violets showed that achromobactin production contributes to the virulence of E. chrysanthemi. Thus, during infection, synthesis of these two different siderophores allows E. chrysanthemi cells to cope with the fluctuations of iron availability encountered within plant tissues. Interestingly, iron transport mediated by achromobactin or a closely related siderophore probably exists in other phytopathogenic bacterial species such as Pseudomonas syringae.
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Affiliation(s)
- Thierry Franza
- Laboratoire de Pathologie Végétale, UMR 217 INRA/INA P-G/UPMC, 16 rue Claude Bernard, 75005 Paris, France
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Benson HP, Boncompagni E, Guerinot ML. An iron uptake operon required for proper nodule development in the Bradyrhizobium japonicum-soybean symbiosis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:950-9. [PMID: 16167765 DOI: 10.1094/mpmi-18-0950] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Rhizobia live in the soil or enter into a nitrogen-fixing symbiosis with a suitable host plant. Each environment presents different challenges with respect to iron acquisition. The soybean symbiont Bradyrhizobium japonicum 61A152 can utilize a variety of siderophores (Fe[III]-specific ligands). Purification of iron-regulated outer membrane proteins had previously allowed the cloning of a gene, fegA, from B. japonicum 61A152, whose predicted protein shares significant amino acid similarity with known TonB-dependent siderophore receptors. Here, we show that fegA is in an operon with a gene, fegB, that is predicted to encode an inner membrane protein. Characterization of fegAB and fegB mutants shows that bothfegA and fegB are required for utilization of the siderophore ferrichrome. Whereas thefegB mutant forms a normal symbiosis, the fegAB mutant has a dramatic phenotype in planta. Six weeks after inoculation with a fegAB strain, soybean nodules do not contain leghemoglobin and do not fix nitrogen. Infected cells contain few symbiosomes and are filled with vesicles. As ferrichrome is a fungal siderophore not likely to be available in nodules, the symbiotic defect suggests that the fegAB operon is serving a different function in planta, possibly one involved in signaling between the two partners.
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Affiliation(s)
- Heather P Benson
- Department of Biological Sciences, 6044 Gilman, Dartmouth College, Hanover, NH 03755, USA
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Fernández L, Márquez I, Guijarro JA. Identification of specific in vivo-induced (ivi) genes in Yersinia ruckeri and analysis of ruckerbactin, a catecholate siderophore iron acquisition system. Appl Environ Microbiol 2004; 70:5199-207. [PMID: 15345400 PMCID: PMC520893 DOI: 10.1128/aem.70.9.5199-5207.2004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Accepted: 05/27/2004] [Indexed: 11/20/2022] Open
Abstract
This work reports the utilization of an in vivo expression technology system to identify in vivo-induced (ivi) genes in Yersinia ruckeri after determination of the conditions needed for its selection in fish. Fourteen clones were selected, and the cloned DNA fragments were analyzed after partial sequencing. In addition to sequences with no significant similarity, homology with genes encoding proteins putatively involved in two-component and type IV secretion systems, adherence, specific metabolic functions, and others were found. Among these sequences, four were involved in iron acquisition through a catechol siderophore (ruckerbactin). Thus, unlike other pathogenic yersiniae producing yersiniabactin, Y. ruckeri might be able to produce and utilize only this phenolate. The genetic organization of the ruckerbactin biosynthetic and uptake loci was similar to that of the Escherichia coli enterobactin gene cluster. Genes rucC and rupG, putative counterparts of E. coli entC and fepG, respectively, involved in the biosynthesis and transport of the iron siderophore complex, respectively, were analyzed further. Thus, regulation of expression by iron and temperature and their presence in other Y. ruckeri siderophore-producing strains were confirmed for these two loci. Moreover, 50% lethal dose values 100-fold higher than those of the wild-type strain were obtained with the rucC isogenic mutant, showing the importance of ruckerbactin in the pathogenesis caused by this microorganism.
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Affiliation(s)
- L Fernández
- Microbiologia, Facultad de Medicina, Universidad de Oviedo, 33006 Oviedo, Asturias, Spain.
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Franza T, Michaud-Soret I, Piquerel P, Expert D. Coupling of iron assimilation and pectinolysis in Erwinia chrysanthemi 3937. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2002; 15:1181-1191. [PMID: 12423024 DOI: 10.1094/mpmi.2002.15.11.1181] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Two major virulence determinants of the plant-pathogenic enterobacterium Erwinia chrysanthemi strain 3937 are the production of pectate lyase enzymes that degrade plant cell walls and expression of two high-affinity iron uptake systems mediated by two structurally unrelated siderophores, chrysobactin and achromobactin. Low iron availability is a signal that triggers transcription of the genes encoding pectate lyases PelD and PelE as well as that of genes involved in iron transport. This metalloregulation is mediated by the transcriptional repressor Fur. In this study, we analyzed the molecular mechanisms of this control. We purified the Erwinia chrysanthemi Fur protein. Band shift assays showed that Fur specifically binds in vitro to the regulatory regions of the genes encoding the ferrichrysobactin outer membrane receptor Fct and the pectate lyases PelD and PelE. We identified the Fur-binding sites of these promoter regions by performing DNase I footprinting experiments. From these data, we propose that Fur could inhibit the activation of the pelD and pelE genes by the cAMP receptor protein CRP according to an anti-activation mechanism. To identify other possible effectors involved in this control, we screened a bank of insertion mutants for an increase in transcriptional activity of pelD and fct genes in response to iron limitation. We isolated a mutant affected in the kdgK gene encoding the 2-keto-3-deoxygluconate (KDG) kinase, an enzyme involved in pectin catabolism. The growth of this mutant in the presence of pectic compounds led to a constitutive expression of iron transport genes as well as complete derepression of the pectinolysis genes. This effect was caused by intracellular accumulation of KDG. However, the derepression of iron transport genes by KDG does not involve the KdgR regulator of pectinolysis genes, which uses KDG as inducer. Thus, in Erwinia chrysanthemi, iron depletion or presence of KDG induces transcription of the genes involved in iron assimilation and pectinolysis. These important pathogenicity functions are coregulated by responding to common signals encountered in planta.
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Affiliation(s)
- Thierry Franza
- Laboratoire de Pathologie Végétale UMR 217 INRA/INA-PG/Université Paris 6, France.
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11
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Rauscher L, Expert D, Matzanke BF, Trautwein AX. Chrysobactin-dependent iron acquisition in Erwinia chrysanthemi. Functional study of a homolog of the Escherichia coli ferric enterobactin esterase. J Biol Chem 2002; 277:2385-95. [PMID: 11694506 DOI: 10.1074/jbc.m107530200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Under iron limitation, the plant pathogen Erwinia chrysanthemi produces the catechol-type siderophore chrysobactin, which acts as a virulence factor. It can also use enterobactin as a xenosiderophore. We began this work by sequencing the 5'-upstream region of the fct-cbsCEBA operon, which encodes the ferric chrysobactin receptor and proteins involved in synthesis of the catechol moiety. We identified a new iron-regulated gene (cbsH) transcribed divergently relative to the fct gene, the translated sequence of which is 45.6% identical to that of Escherichia coli ferric enterobactin esterase. Insertions within this gene interrupt the chrysobactin biosynthetic pathway by exerting a polar effect on a downstream gene with some sequence identity to the E. coli enterobactin synthase gene. These mutations had no effect on the ability of the bacterium to obtain iron from enterobactin, showing that a functional cbsH gene is not required for iron removal from ferric enterobactin in E. chrysanthemi. The cbsH-negative mutants were less able to utilize ferric chrysobactin, and this effect was not caused by a defect in transport per se. In a nonpolar cbsH-negative mutant, chrysobactin accumulated intracellularly. These defects were rescued by the cbsH gene supplied on a plasmid. The amino acid sequence of the CbsH protein revealed characteristics of the S9 prolyl oligopeptidase family. Ferric chrysobactin hydrolysis was detected in cell extracts from a cbsH-positive strain that was inhibited by diisopropyl fluorophosphate. These data are consistent with the fact that chrysobactin is a d-lysyl-l-serine derivative. Mössbauer spectroscopy of whole cells at various states of (57)Fe-labeled chrysobactin uptake showed that this enzyme is not required for iron removal from chrysobactin in vivo. The CbsH protein may therefore be regarded as a peptidase that prevents the bacterial cells from being intracellularly iron-depleted by chrysobactin.
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Affiliation(s)
- Lise Rauscher
- Laboratoire de Pathologie Végétale, UMR 217 Institut National de la Recherche Agronomique, Institut National Agronomique Paris-Grignon, Université Paris 6, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
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Rogers MB, Sexton JA, DeCastro GJ, Calderwood SB. Identification of an operon required for ferrichrome iron utilization in Vibrio cholerae. J Bacteriol 2000; 182:2350-3. [PMID: 10735886 PMCID: PMC111292 DOI: 10.1128/jb.182.8.2350-2353.2000] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutagenesis of Vibrio cholerae with TnphoA, followed by screening for fusions that were activated under low-iron conditions, led to the identification of seven independent fusion strains, each of which was deficient in the ability to utilize ferrichrome as a sole iron source for growth in a plate bioassay and had an insertion in genes encoding products homologous to Escherichia coli FhuA or FhuD. Expression of the gene fusions was independent of IrgB but regulated by Fur. We report here a map of the operon and the predicted amino acid sequence of FhuA, based on the nucleotide sequence. Unlike those of the E. coli fhu operon, the V. cholerae ferrichrome utilization genes are located adjacent and opposite in orientation to a gene encoding an ATP-binding cassette transporter homolog, but this gene, if disrupted, does not affect the utilization of ferrichrome in vitro.
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Affiliation(s)
- M B Rogers
- Infectious Disease Division, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
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Franza T, Sauvage C, Expert D. Iron regulation and pathogenicity in Erwinia chrysanthemi 3937: role of the Fur repressor protein. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 1999; 12:119-28. [PMID: 9926414 DOI: 10.1094/mpmi.1999.12.2.119] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Low iron availability is a triggering signal for coordinated expression of the genes encoding pectate lyases PelB, PelC, PelD, and PelE, and chrysobactin iron transport functions, which are two main determinants of phytopathogenicity of the Erwinia chrysanthemi strain 3937. The possible implication of the ferric uptake regulation (Fur) protein in this process was investigated. The E. chrysanthemi fur gene was cloned by functional complementation of an Escherichia coli fur mutant and sequenced. The 444-bp open reading frame identified was found to code for a protein highly similar to the E. coli Fur regulator. An E. chrysanthemi fur null mutant was constructed by reverse genetics. This mutant showed altered growth capacity and reduced pathogenicity on African violets. In a fur background, transcriptional lacZ fusions to genes belonging to the E. chrysanthemi high affinity iron transport systems were constitutively expressed. Transcription of the pelA, pelD, and pelE genes was analyzed, using fusions to the uidA reporter gene. Iron availability and a fur mutation did not influence the expression of pelA. In the presence of iron, pelD and pelE transcription levels were higher in the fur mutant than in the parental strain. Furthermore, iron deficiency stimulated the expression of both fusions in the fur mutant. These findings indicate that, in E. chrysanthemi 3937, (i) Fur negatively controls iron transport and genes encoding PelD and PelE, and (ii) additional factor(s) mediate iron regulation of the pel genes.
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Affiliation(s)
- T Franza
- Laboratoire de Pathologie Végétale, INA P-G/INRA, Paris, France.
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Expert D. WITHHOLDING AND EXCHANGING IRON: Interactions Between Erwinia spp. and Their Plant Hosts. ANNUAL REVIEW OF PHYTOPATHOLOGY 1999; 37:307-334. [PMID: 11701826 DOI: 10.1146/annurev.phyto.37.1.307] [Citation(s) in RCA: 115] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The critical role of iron in plant host-parasite relationships has been elucidated in diseases as different as the soft rot and fire blight incited by Erwinia chrysanthemi and E. amylovora, respectively. As in animal infections, the role of iron and its ligands in the virulence of plant pathogens seems to be more subtle than might be expected, and is intimately related to the life cycle of the pathogen within its host. This review discusses how iron, because of its unique position in biological systems, controls the activities of these plant pathogens. Molecular studies illustrating the key question of iron acquisition and homeostasis during pathogenesis are described. The production of siderophores by pathogens not only represents a powerful strategy to acquire iron from host tissues but may also act as a protective agent against iron toxicity. The need of the host to bind and possibly sequester the metal during pathogenesis is another central issue. Possible modes of iron competition between plant host and pathogen are considered.
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Affiliation(s)
- D Expert
- Pathologie Végétale, INRA/CNRS, Institut National Agronomique, 16 rue Claude Bernard, Paris, F-75231 France; e-mail:
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Hugouvieux-Cotte-Pattat N, Condemine G, Nasser W, Reverchon S. Regulation of pectinolysis in Erwinia chrysanthemi. Annu Rev Microbiol 1996; 50:213-57. [PMID: 8905080 DOI: 10.1146/annurev.micro.50.1.213] [Citation(s) in RCA: 255] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Erwinia chrysanthemi is an enterobacterium that causes various plant diseases. Its pathogenicity results from the secretion of pectinolytic enzymes responsible for the disorganization of the plant cell wall. The E. chrysanthemi strain 3937 produces two pectin methylesterases, at least seven pectate lyases, a polygalacturonase, and a pectin lyase. The extracellular degradation of the pectin leads to the formation of oligogalacturonides that are catabolized through an intracellular pathway. The pectinase genes are expressed from independent cistrons, and their transcription is favored by environmental conditions such as presence of pectin and plant extracts, stationary growth phase, low temperature, oxygen or iron limitation, and so on. Moreover, transcription of the pectin lyase gene responds to DNA-damaging agents. The differential expressions of individual pectinase genes presumably reflect their role during plant infection. The regulation of pel genes requires several regulatory systems, including the KdgR repressor, which mediates the induction of all the pectinolysis genes in the presence of pectin catabolites. KdgR also controls the genes necessary for pectinase secretion and other pectin-inducible genes not yet characterized. PecS, a cytoplasmic protein homologous to other transcriptional regulators, can bind in vitro to the regulatory regions of pectinase and cellulase genes. The PecT protein, a member of the LysR family of transcriptional regulators, represses the expression of some pectinase genes and also affects other metabolic pathways of the bacteria. Other proteins involved in global regulations, such as CRP or HNS, can bind to the regulatory regions of the pectinase genes and affect their transcription.
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