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Liu J, Wang Z, Zeng Y, Wang W, Tang S, Jia A. 1H-Pyrrole-2,5-dicarboxylic acid, a quorum sensing inhibitor from one endophytic fungus in Areca catechu L., acts as antibiotic accelerant against Pseudomonas aeruginosa. Front Cell Infect Microbiol 2024; 14:1413728. [PMID: 39015339 PMCID: PMC11250523 DOI: 10.3389/fcimb.2024.1413728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Accepted: 05/27/2024] [Indexed: 07/18/2024] Open
Abstract
Pseudomonas aeruginosa has already been stipulated as a "critical" pathogen, emphasizing the urgent need for researching and developing novel antibacterial agents due to multidrug resistance. Bacterial biofilm formation facilitates cystic fibrosis development and restricts the antibacterial potential of many current antibiotics. The capacity of P. aeruginosa to form biofilms and resist antibiotics is closely correlated with quorum sensing (QS). Bacterial QS is being contemplated as a promising target for developing novel antibacterial agents. QS inhibitors are a promising strategy for treating chronic infections. This study reported that the active compound PT22 (1H-pyrrole-2,5-dicarboxylic acid) isolated from Perenniporia tephropora FF2, one endophytic fungus from Areca catechu L., presents QS inhibitory activity against P. aeruginosa. Combined with gentamycin or piperacillin, PT22 functions as a novel antibiotic accelerant against P. aeruginosa. PT22 (0.50 mg/mL, 0.75 mg/mL, and 1.00 mg/mL) reduces the production of QS-related virulence factors, such as pyocyanin and rhamnolipid, and inhibits biofilm formation of P. aeruginosa PAO1 instead of affecting its growth. The architectural disruption of the biofilms was confirmed by visualization through scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). Real-time quantitative PCR (RT-qPCR) indicated that PT22 significantly attenuated the expression of QS-related genes followed by docking analysis of molecules against QS activator proteins. PT22 dramatically increased the survival rate of Galleria mellonella. PT22 combined with gentamycin or piperacillin presents significant inhibition of biofilm formation and eradication of mature biofilm compared to monotherapy, which was also confirmed by visualization through SEM and CLSM. After being treated with PT22 combined with gentamycin or piperacillin, the survival rates of G. mellonella were significantly increased compared to those of monotherapy. PT22 significantly enhanced the susceptibility of gentamycin and piperacillin against P. aeruginosa PAO1. Our results suggest that PT22 from P. tephropora FF2 as a potent QS inhibitor is a candidate antibiotic accelerant to combat the antibiotic resistance of P. aeruginosa.
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Affiliation(s)
- Junsheng Liu
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou, China
- Hainan General Hospital, Hainan Affiliated Hospital of Hainan Medical University, Haikou, China
| | - Zhennan Wang
- Modern Industrial College of Traditional Chinese Medicine and Health, Lishui University, Lishui, China
| | - Yuexiang Zeng
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou, China
| | - Wei Wang
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou, China
| | - Shi Tang
- Key Laboratory of Tropical Biological Resources of Ministry of Education, School of Pharmaceutical Sciences, Hainan University, Haikou, China
| | - Aiqun Jia
- Hainan General Hospital, Hainan Affiliated Hospital of Hainan Medical University, Haikou, China
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2
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Song Y, Wu X, Li Z, Ma QQ, Bao R. Molecular mechanism of siderophore regulation by the Pseudomonas aeruginosa BfmRS two-component system in response to osmotic stress. Commun Biol 2024; 7:295. [PMID: 38461208 PMCID: PMC10924945 DOI: 10.1038/s42003-024-05995-z] [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: 11/13/2023] [Accepted: 02/29/2024] [Indexed: 03/11/2024] Open
Abstract
Pseudomonas aeruginosa, a common nosocomial pathogen, relies on siderophores to acquire iron, crucial for its survival in various environments and during host infections. However, understanding the molecular mechanisms of siderophore regulation remains incomplete. In this study, we found that the BfmRS two-component system, previously associated with biofilm formation and quorum sensing, is essential for siderophore regulation under high osmolality stress. Activated BfmR directly bound to the promoter regions of pvd, fpv, and femARI gene clusters, thereby activating their transcription and promoting siderophore production. Subsequent proteomic and phenotypic analyses confirmed that deletion of BfmRS reduces siderophore-related proteins and impairs bacterial survival in iron-deficient conditions. Furthermore, phylogenetic analysis demonstrated the high conservation of the BfmRS system across Pseudomonas species, functional evidences also indicated that BfmR homologues from Pseudomonas putida KT2440 and Pseudomonas sp. MRSN12121 could bind to the promoter regions of key siderophore genes and osmolality-mediated increases in siderophore production were observed. This work illuminates a novel signaling pathway for siderophore regulation and enhances our understanding of siderophore-mediated bacterial interactions and community establishment.
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Affiliation(s)
- Yingjie Song
- College of Life Science, Sichuan Normal University, Chengdu, 610101, China
| | - Xiyu Wu
- Advanced Mass Spectrometry Center, Research Core Facility, Frontiers Science Center for Disease-related Molecular Network, West China Hospital, Sichuan University, Chengdu, 610213, China
| | - Ze Li
- Center of Infectious Diseases, Division of Infectious Diseases in State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, China
| | - Qin Qin Ma
- College of Life Science, Sichuan Normal University, Chengdu, 610101, China
| | - Rui Bao
- Center of Infectious Diseases, Division of Infectious Diseases in State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, 610041, China.
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Kubori T. A two-component system serves as a central hub for connecting energy metabolism and plasmid dissemination in bacteria. mBio 2023; 14:e0247423. [PMID: 38032214 PMCID: PMC10746237 DOI: 10.1128/mbio.02474-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023] Open
Abstract
Mobile genetic elements such as conjugative plasmids play a key role in the acquisition of antibiotic resistance by pathogenic bacteria. Resistance genes on plasmids can be transferred between bacteria using specialized conjugation machinery. Acinetobacter baumannii, the most common bacterium associated with nosocomial infections, harbors a large conjugative plasmid that encodes a type IV secretion system (T4SS). Feng et al. recently found that the A. baumannii T4SS is specialized for plasmid transfer, suggesting that it may be involved in multidrug resistance (Z. Feng, L. Wang, Q. Guan, X. Chu, and Z.-Q. Luo, mBio e02276-23, 2023, https://doi.org/10.1128/mbio.02276-23), T4SS-encoding genes are shown to be controlled by a versatile GacA/S two-component regulatory system. GacA/S is also found to regulate genes involved in central metabolism. The coordinated regulation of metabolism and plasmid conjugation may be a bacterial strategy for adapting to selective pressure from antibiotics.
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Affiliation(s)
- Tomoko Kubori
- Department of Microbiology, Graduate School of Medicine, Gifu University, Gifu, Japan
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Teng S, Wu T, Gao D, Wu S, Xiao Y, Long Y, Xie Z. Insight into the Global Negative Regulation of Iron Scavenger 7-HT Biosynthesis by the SigW/RsiW System in Pseudomonas donghuensis HYS. Int J Mol Sci 2023; 24:ijms24021184. [PMID: 36674714 PMCID: PMC9861184 DOI: 10.3390/ijms24021184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 01/04/2023] [Accepted: 01/05/2023] [Indexed: 01/11/2023] Open
Abstract
7-Hydroxytropolone (7-HT) is a unique iron scavenger synthesized by Pseudomonas donghuensis HYS that has various biological activities in addition to functioning as a siderophore. P. donghuensis HYS is more pathogenic than P. aeruginosa toward Caenorhabditis elegans, an observation that is closely linked to the biosynthesis of 7-HT. The nonfluorescent siderophore (nfs) gene cluster is responsible for the orderly biosynthesis of 7-HT and represents a competitive advantage that contributes to the increased survival of P. donghuensis HYS; however, the regulatory mechanisms of 7-HT biosynthesis remain unclear. This study is the first to propose that the ECF σ factor has a regulatory effect on 7-HT biosynthesis. In total, 20 ECF σ factors were identified through genome-wide scanning, and their responses to extracellular ferrous ions were characterized. We found that SigW was both significantly upregulated under high-iron conditions and repressed by an adjacent anti-σ factor. RNA-Seq results suggest that the SigW/RsiW system is involved in iron metabolism and 7-HT biosynthesis. Combined with the siderophore phenotype, we also found that SigW could inhibit siderophore synthesis, and this inhibition can be relieved by RsiW. EMSA assays proved that SigW, when highly expressed, can directly bind to the promoter region of five operons of the nfs cluster to inhibit the transcription of the corresponding genes and consequently suppress 7-HT biosynthesis. In addition, SigW not only directly negatively regulates structural genes related to 7-HT synthesis but also inhibits the transcription of regulatory proteins, including of the Gac/Rsm cascade system. Taken together, our results highlight that the biosynthesis of 7-HT is negatively regulated by SigW and that the SigW/RsiW system is involved in mechanisms for the regulation of iron homeostasis in P. donghuensis HYS. As a result of this work, we identified a novel mechanism for the global negative regulation of 7-HT biosynthesis, complementing our understanding of the function of ECF σ factors in Pseudomonas.
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Singkham-In U, Phuengmaung P, Makjaroen J, Saisorn W, Bhunyakarnjanarat T, Chatsuwan T, Chirathaworn C, Chancharoenthana W, Leelahavanichkul A. Chlorhexidine Promotes Psl Expression in Pseudomonas aeruginosa That Enhances Cell Aggregation with Preserved Pathogenicity Demonstrates an Adaptation against Antiseptic. Int J Mol Sci 2022; 23:ijms23158308. [PMID: 35955437 PMCID: PMC9368580 DOI: 10.3390/ijms23158308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 07/20/2022] [Accepted: 07/25/2022] [Indexed: 11/16/2022] Open
Abstract
Because Pseudomonas aeruginosa is frequently in contact with Chlorhexidine (a regular antiseptic), bacterial adaptations are possible. In comparison with the parent strain, the Chlorhexidine-adapted strain formed smaller colonies with metabolic downregulation (proteomic analysis) with the cross-resistance against colistin (an antibiotic for several antibiotic-resistant bacteria), partly through the modification of L-Ara4N in the lipopolysaccharide at the outer membrane. Chlorhexidine-adapted strain formed dense liquid–solid interface biofilms with enhanced cell aggregation partly due to the Chlorhexidine-induced overexpression of psl (exopolysaccharide-encoded gene) through the LadS/GacSA pathway (c-di-GMP-independence) in 12 h biofilms and maintained the aggregation with SiaD-mediated c-di-GMP dependence in 24 h biofilms as evaluated by polymerase chain reaction (PCR). The addition of Ca2+ in the Chlorhexidine-adapted strain facilitated several Psl-associated genes, indicating an impact of Ca2+ in Psl production. The activation by Chlorhexidine-treated sessile bacteria demonstrated a lower expression of IL-6 and IL-8 on fibroblasts and macrophages than the activation by the parent strain, indicating the less inflammatory reactions from Chlorhexidine-exposed bacteria. However, the 14-day severity of the wounds in mouse caused by Chlorhexidine-treated bacteria versus the parent strain was similar, as indicated by wound diameters and bacterial burdens. In conclusion, Chlorhexidine induced psl over-expression and colistin cross-resistance that might be clinically important.
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Affiliation(s)
- Uthaibhorn Singkham-In
- Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand; (U.S.-I.); (P.P.); (C.C.)
| | - Pornpimol Phuengmaung
- Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand; (U.S.-I.); (P.P.); (C.C.)
| | - Jiradej Makjaroen
- Center of Excellence in Systems Biology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand;
| | - Wilasinee Saisorn
- Translational Research in Inflammation and Immunology Research Unit (TRIRU), Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand; (W.S.); (T.B.)
| | - Thansita Bhunyakarnjanarat
- Translational Research in Inflammation and Immunology Research Unit (TRIRU), Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand; (W.S.); (T.B.)
| | - Tanittha Chatsuwan
- Antimicrobial Resistance and Stewardship Research Unit, Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand;
| | - Chintana Chirathaworn
- Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand; (U.S.-I.); (P.P.); (C.C.)
| | - Wiwat Chancharoenthana
- Tropical Nephrology Research Unit, Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok 10400, Thailand
- Correspondence: (W.C.); (A.L.); Tel.: +66-2-306-9130 (W.C.); +66-2-256-4251 (A.L.); Fax: +66-2-354-9150 (W.C.); +66-2-252-6920 (A.L.)
| | - Asada Leelahavanichkul
- Translational Research in Inflammation and Immunology Research Unit (TRIRU), Department of Microbiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama 4 Road, Pathumwan, Bangkok 10330, Thailand; (W.S.); (T.B.)
- Correspondence: (W.C.); (A.L.); Tel.: +66-2-306-9130 (W.C.); +66-2-256-4251 (A.L.); Fax: +66-2-354-9150 (W.C.); +66-2-252-6920 (A.L.)
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6
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Hall KM, Pursell ZF, Morici LA. The role of the Pseudomonas aeruginosa hypermutator phenotype on the shift from acute to chronic virulence during respiratory infection. Front Cell Infect Microbiol 2022; 12:943346. [PMID: 35937684 PMCID: PMC9355025 DOI: 10.3389/fcimb.2022.943346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 06/30/2022] [Indexed: 11/13/2022] Open
Abstract
Chronic respiratory infection (CRI) with Pseudomonas aeruginosa (Pa) presents many unique challenges that complicate treatment. One notable challenge is the hypermutator phenotype which is present in up to 60% of sampled CRI patient isolates. Hypermutation can be caused by deactivating mutations in DNA mismatch repair (MMR) genes including mutS, mutL, and uvrD. In vitro and in vivo studies have demonstrated hypermutator strains to be less virulent than wild-type Pa. However, patients colonized with hypermutators display poorer lung function and a higher incidence of treatment failure. Hypermutation and MMR-deficiency create increased genetic diversity and population heterogeneity due to elevated mutation rates. MMR-deficient strains demonstrate higher rates of mucoidy, a hallmark virulence determinant of Pa during CRI in cystic fibrosis patients. The mucoid phenotype results from simple sequence repeat mutations in the mucA gene made in the absence of functional MMR. Mutations in Pa are further increased in the absence of MMR, leading to microcolony biofilm formation, further lineage diversification, and population heterogeneity which enhance bacterial persistence and host immune evasion. Hypermutation facilitates the adaptation to the lung microenvironment, enabling survival among nutritional complexity and microaerobic or anaerobic conditions. Mutations in key acute-to-chronic virulence “switch” genes, such as retS, bfmS, and ampR, are also catalyzed by hypermutation. Consequently, strong positive selection for many loss-of-function pathoadaptive mutations is seen in hypermutators and enriched in genes such as lasR. This results in the characteristic loss of Pa acute infection virulence factors, including quorum sensing, flagellar motility, and type III secretion. Further study of the role of hypermutation on Pa chronic infection is needed to better inform treatment regimens against CRI with hypermutator strains.
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Affiliation(s)
- Kalen M. Hall
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, United States
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Zachary F. Pursell
- Department of Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA, United States
| | - Lisa A. Morici
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, United States
- *Correspondence: Lisa A. Morici,
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7
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RetS Regulates Phage Infection in Pseudomonas aeruginosa via Modulating the GacS/GacA Two-Component System. J Virol 2022; 96:e0019722. [PMID: 35348363 DOI: 10.1128/jvi.00197-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In Pseudomonas aeruginosa, the complex multisensing regulatory networks RetS-GacS/GacA have been demonstrated to play key roles in controlling the switch between planktonic and sessile lifestyles. However, whether this multisensing system is involved in the regulation of phage infection has not been investigated. Here, we provide a link between the sensors RetS/GacS and infection of phages vB_Pae_QDWS and vB_Pae_W3. Our data suggest that the sensors kinases RetS and GacS in Pseudomonas aeruginosa play opposite regulatory functions on phage infection. Mutation in retS increased phage resistance. Cellular levels of RsmY and RsmZ increased in PaΔretS and were positively correlated with phage resistance. Further analysis demonstrated that RetS regulated phage infection by affecting the type IV pilus (T4P)-mediated adsorption. The regulation of RetS on phage infection depends on the GacS/GacA two-component system and is likely a dynamic process in response to environmental signals. The findings offer additional support for the rapid emergence of phage resistance. IMPORTANCE Our knowledge on the molecular mechanisms behind bacterium-phage interactions remains limited. Our study reported that the complex multisensing regulatory networks RetS-GacS/GacA of Pseudomonas aeruginosa PAO1 play key roles in controlling phage infection. The main observation was that the mutation in RetS could result in increased phage resistance by reducing the type IV pilus-mediated phage adsorption. The bacterial defense strategy is generally applicable to various phages since many P. aeruginosa phages can use type IV pilus as their receptors. The results also suggest that the phage infection is likely to be regulated dynamically, which depends on the environmental stimuli. Reduction of the signals that RetS favors would increase phage resistance. Our study is particularly remarkable for uncovering a signal transduction system that was involved in phage infection, which may help in filling some knowledge gaps in this field.
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López-Pliego L, Lara-Flores N, Molina-Romero D, May-Compañ G, Carreño-López R, Núñez CE, Castañeda M. The GacS/A-Rsm Pathway Positively Regulates Motility and Flagella Synthesis in Azotobacter vinelandii. Curr Microbiol 2021; 79:17. [PMID: 34905080 DOI: 10.1007/s00284-021-02695-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 10/21/2021] [Indexed: 10/19/2022]
Abstract
Azotobacter vinelandii is a motile bacterium that possesses an unusual pattern of peritrichous flagellation for members of the Pseudomonadaceae family. Unlike what has been reported for Pseudomonas spp. FleQ is not the master regulator of motility in A. vinelandii, this role is performed by FlhDC. Other factors involved in the regulation of motility are AlgU (σE) and CydR which act as negative regulators. In some members of the Enterobacteriaceae and Pseudomonadaceae families, the GacS/A-Rsm pathway is another important factor regulating motility. In the present study, the involvement of the GacS/A-Rsm pathway in regulating the motility of A. vinelandii was explored; we found that contrary to what has been reported for most of the strains studied of Pseudomonas species, GacS/A, through the Rsm system, positively controlled swimming motility. We show that the target of this regulation is the synthesis of flagella, which most likely occurs in an FlhDC-independent manner.
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Affiliation(s)
- Liliana López-Pliego
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México
| | - Norarizbeth Lara-Flores
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México.,Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, 13 Sur 2702, C. P. 72410, Puebla, Pue, México
| | - Dalia Molina-Romero
- Facultad de Ciencias Biológicas, BIO-1 Ciudad Universitaria, C. P. 72000, Puebla, Pue, México
| | - Gabriela May-Compañ
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México.,Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, 13 Sur 2702, C. P. 72410, Puebla, Pue, México
| | - Ricardo Carreño-López
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México
| | - Cinthia E Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, C. P. 62250, Cuernavaca, Mor, México
| | - Miguel Castañeda
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México.
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9
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Effective In Vitro Control of Two Phytopathogens of Agricultural Interest Using Cell-Free Extracts of Pseudomonas fluorescens and Chitosan. Molecules 2021; 26:molecules26216359. [PMID: 34770767 PMCID: PMC8588211 DOI: 10.3390/molecules26216359] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/25/2021] [Accepted: 09/27/2021] [Indexed: 11/16/2022] Open
Abstract
A biofungicide is a natural product that can be derived from various sources such as, among others, microorganisms, higher plants, animal products, phytochemicals, semiochemicals, and antagonist microorganisms. One of the most important approaches for the production of biofungicides is the combination of biocontrol agents. This study showed the inhibition growth of Alternaria alternata and Fusarium solani treated with cell-free extracts of P. fluorescens. Using thin-layer chromatography and plate assays it was also demonstrated that the cell-free extracts of P. fluorescens contained siderophores and derivates of 4-diacetylphloroglucinol and phenazine. Moreover, the combination of cell-free extracts of P. fluorescens and chitosan [50–1.5% (v/v)] had a synergistic effect since they notably inhibited the mycelial growth of A. altenata and F. solani. Various morphological alterations to the mycelia and conidia of the treated fungi as a result of this combination were also observed. The present study could be a starting point to control other fungal phytopathogens using different cell-free extracts and chitosan as biocontrol agents.
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Ryan Kaler KM, Nix JC, Schubot FD. RetS inhibits Pseudomonas aeruginosa biofilm formation by disrupting the canonical histidine kinase dimerization interface of GacS. J Biol Chem 2021; 297:101193. [PMID: 34529974 PMCID: PMC8498467 DOI: 10.1016/j.jbc.2021.101193] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/30/2021] [Accepted: 09/10/2021] [Indexed: 12/15/2022] Open
Abstract
Bacterial signaling histidine kinases (HKs) have long been postulated to function exclusively through linear signal transduction chains. However, several HKs have recently been shown to form complex multikinase networks (MKNs). The most prominent MKN, involving the enzymes RetS and GacS, controls the switch between the motile and biofilm lifestyles in the pathogenic bacterium Pseudomonas aeruginosa. While GacS promotes biofilm formation, RetS counteracts GacS using three distinct mechanisms. Two are dephosphorylating mechanisms. The third, a direct binding between the RetS and GacS HK regions, blocks GacS autophosphorylation. Focusing on the third mechanism, we determined the crystal structure of a cocomplex between the HK region of RetS and the dimerization and histidine phosphotransfer (DHp) domain of GacS. This is the first reported structure of a complex between two distinct bacterial signaling HKs. In the complex, the canonical HK homodimerization interface is replaced by a strikingly similar heterodimeric interface between RetS and GacS. We further demonstrate that GacS autophosphorylates in trans, thus explaining why the formation of a RetS-GacS complex inhibits GacS autophosphorylation. Using mutational analysis in conjunction with bacterial two-hybrid and biofilm assays, we not only corroborate the biological role of the observed RetS-GacS interactions, but also identify a residue critical for the equilibrium between the RetS-GacS complex and the respective RetS and GacS homodimers. Collectively, our findings suggest that RetS and GacS form a domain-swapped hetero-oligomer during the planktonic growth phase of P. aeruginosa before unknown signals cause its dissociation and a relief of GacS inhibition to promote biofilm formation.
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Affiliation(s)
- Kylie M Ryan Kaler
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Jay C Nix
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Florian D Schubot
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.
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11
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Drabinska J, Steczkiewicz K, Kujawa M, Kraszewska E. Searching for Biological Function of the Mysterious PA2504 Protein from Pseudomonas aeruginosa. Int J Mol Sci 2021; 22:ijms22189833. [PMID: 34575996 PMCID: PMC8466066 DOI: 10.3390/ijms22189833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/08/2021] [Accepted: 09/09/2021] [Indexed: 11/16/2022] Open
Abstract
For nearly half of the proteome of an important pathogen, Pseudomonas aeruginosa, the function has not yet been recognised. Here, we characterise one such mysterious protein PA2504, originally isolated by us as a sole partner of the RppH RNA hydrolase involved in transcription regulation of multiple genes. This study aims at elucidating details of PA2504 function and discussing its implications for bacterial biology. We show that PA2504 forms homodimers and is evenly distributed in the cytoplasm of bacterial cells. Molecular modelling identified the presence of a Tudor-like domain in PA2504. Transcriptomic analysis of a ΔPA2504 mutant showed that 42 transcripts, mainly coding for proteins involved in sulphur metabolism, were affected by the lack of PA2504. In vivo crosslinking of cellular proteins in the exponential and stationary phase of growth revealed several polypeptides that bound to PA2504 exclusively in the stationary phase. Mass spectrometry analysis identified them as the 30S ribosomal protein S4, the translation elongation factor TufA, and the global response regulator GacA. These results indicate that PA2504 may function as a tether for several important cellular factors.
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12
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Li E, de Jonge R, Liu C, Jiang H, Friman VP, Pieterse CMJ, Bakker PAHM, Jousset A. Rapid evolution of bacterial mutualism in the plant rhizosphere. Nat Commun 2021; 12:3829. [PMID: 34158504 PMCID: PMC8219802 DOI: 10.1038/s41467-021-24005-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 05/24/2021] [Indexed: 02/07/2023] Open
Abstract
While beneficial plant-microbe interactions are common in nature, direct evidence for the evolution of bacterial mutualism is scarce. Here we use experimental evolution to causally show that initially plant-antagonistic Pseudomonas protegens bacteria evolve into mutualists in the rhizosphere of Arabidopsis thaliana within six plant growth cycles (6 months). This evolutionary transition is accompanied with increased mutualist fitness via two mechanisms: (i) improved competitiveness for root exudates and (ii) enhanced tolerance to the plant-secreted antimicrobial scopoletin whose production is regulated by transcription factor MYB72. Crucially, these mutualistic adaptations are coupled with reduced phytotoxicity, enhanced transcription of MYB72 in roots, and a positive effect on plant growth. Genetically, mutualism is associated with diverse mutations in the GacS/GacA two-component regulator system, which confers high fitness benefits only in the presence of plants. Together, our results show that rhizosphere bacteria can rapidly evolve along the parasitism-mutualism continuum at an agriculturally relevant evolutionary timescale.
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Affiliation(s)
- Erqin Li
- grid.5477.10000000120346234Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands ,grid.14095.390000 0000 9116 4836Freie Universität Berlin, Institut für Biologie, Berlin, Germany ,grid.452299.1Berlin-Brandenburg Institute of Advanced Biodiversity Research, Berlin, Germany
| | - Ronnie de Jonge
- grid.5477.10000000120346234Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands ,grid.11486.3a0000000104788040VIB Center for Plant Systems Biology, Ghent, Belgium ,grid.5342.00000 0001 2069 7798Ghent University, Department of Plant Biotechnology and Bioinformatics, Ghent, Belgium
| | - Chen Liu
- grid.5477.10000000120346234Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Henan Jiang
- grid.5477.10000000120346234Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Ville-Petri Friman
- grid.5685.e0000 0004 1936 9668University of York, Department of Biology, York, UK
| | - Corné M. J. Pieterse
- grid.5477.10000000120346234Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Peter A. H. M. Bakker
- grid.5477.10000000120346234Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Alexandre Jousset
- grid.5477.10000000120346234Utrecht University, Department of Biology, Ecology and Biodiversity, Utrecht, The Netherlands
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13
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Li E, de Jonge R, Liu C, Jiang H, Friman VP, Pieterse CMJ, Bakker PAHM, Jousset A. Rapid evolution of bacterial mutualism in the plant rhizosphere. Nat Commun 2021. [PMID: 34158504 DOI: 10.1038/s41467-012-24005-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023] Open
Abstract
While beneficial plant-microbe interactions are common in nature, direct evidence for the evolution of bacterial mutualism is scarce. Here we use experimental evolution to causally show that initially plant-antagonistic Pseudomonas protegens bacteria evolve into mutualists in the rhizosphere of Arabidopsis thaliana within six plant growth cycles (6 months). This evolutionary transition is accompanied with increased mutualist fitness via two mechanisms: (i) improved competitiveness for root exudates and (ii) enhanced tolerance to the plant-secreted antimicrobial scopoletin whose production is regulated by transcription factor MYB72. Crucially, these mutualistic adaptations are coupled with reduced phytotoxicity, enhanced transcription of MYB72 in roots, and a positive effect on plant growth. Genetically, mutualism is associated with diverse mutations in the GacS/GacA two-component regulator system, which confers high fitness benefits only in the presence of plants. Together, our results show that rhizosphere bacteria can rapidly evolve along the parasitism-mutualism continuum at an agriculturally relevant evolutionary timescale.
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Affiliation(s)
- Erqin Li
- Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
- Freie Universität Berlin, Institut für Biologie, Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, Berlin, Germany
| | - Ronnie de Jonge
- Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands.
- VIB Center for Plant Systems Biology, Ghent, Belgium.
- Ghent University, Department of Plant Biotechnology and Bioinformatics, Ghent, Belgium.
| | - Chen Liu
- Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Henan Jiang
- Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | | | - Corné M J Pieterse
- Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Peter A H M Bakker
- Utrecht University, Department of Biology, Plant-Microbe Interactions, Utrecht, The Netherlands
| | - Alexandre Jousset
- Utrecht University, Department of Biology, Ecology and Biodiversity, Utrecht, The Netherlands.
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14
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Ortet P, Fochesato S, Bitbol AF, Whitworth DE, Lalaouna D, Santaella C, Heulin T, Achouak W, Barakat M. Evolutionary history expands the range of signaling interactions in hybrid multikinase networks. Sci Rep 2021; 11:11763. [PMID: 34083699 PMCID: PMC8175716 DOI: 10.1038/s41598-021-91260-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 05/19/2021] [Indexed: 12/02/2022] Open
Abstract
Two-component systems (TCSs) are ubiquitous signaling pathways, typically comprising a sensory histidine kinase (HK) and a response regulator, which communicate via intermolecular kinase-to-receiver domain phosphotransfer. Hybrid HKs constitute non-canonical TCS signaling pathways, with transmitter and receiver domains within a single protein communicating via intramolecular phosphotransfer. Here, we report how evolutionary relationships between hybrid HKs can be used as predictors of potential intermolecular and intramolecular interactions (‘phylogenetic promiscuity’). We used domain-swap genes chimeras to investigate the specificity of phosphotransfer within hybrid HKs of the GacS–GacA multikinase network of Pseudomonas brassicacearum. The receiver domain of GacS was replaced with those from nine donor hybrid HKs. Three chimeras with receivers from other hybrid HKs demonstrated correct functioning through complementation of a gacS mutant, which was dependent on strains having a functional gacA. Formation of functional chimeras was predictable on the basis of evolutionary heritage, and raises the possibility that HKs sharing a common ancestor with GacS might remain components of the contemporary GacS network. The results also demonstrate that understanding the evolutionary heritage of signaling domains in sophisticated networks allows their rational rewiring by simple domain transplantation, with implications for the creation of designer networks and inference of functional interactions.
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Affiliation(s)
- Philippe Ortet
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France
| | - Sylvain Fochesato
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France
| | - Anne-Florence Bitbol
- CNRS, Institut de Biologie Paris-Seine, Laboratoire Jean Perrin (UMR8237), Sorbonne Université, 75005, Paris, France.,Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - David E Whitworth
- Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Ceredigion, SY23 3DD, UK
| | - David Lalaouna
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France.,CNRS, ARN UPR 9002, Université de Strasbourg, 67000, Strasbourg, France
| | - Catherine Santaella
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France
| | - Thierry Heulin
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France
| | - Wafa Achouak
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France
| | - Mohamed Barakat
- Aix Marseille Univ, CEA, CNRS, BIAM, LEMIRE, 13108, Saint Paul-Lez-Durance, France.
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15
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Fungal-Associated Molecules Induce Key Genes Involved in the Biosynthesis of the Antifungal Secondary Metabolites Nunamycin and Nunapeptin in the Biocontrol Strain Pseudomonas fluorescens In5. Appl Environ Microbiol 2020; 86:AEM.01284-20. [PMID: 32826219 DOI: 10.1128/aem.01284-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/12/2020] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas fluorescens In5 synthesizes the antifungal cyclic lipopeptides (CLPs) nunamycin and nunapeptin, which are similar in structure and genetic organization to the pseudomonas-derived phytotoxins syringomycin and syringopeptin. Regulation of syringomycin and syringopeptin is dependent on the two-component global regulatory system GacS-GacA and the SalA, SyrF, and SyrG transcription factors, which activate syringomycin synthesis in response to plant signal molecules. Previously, we demonstrated that a specific transcription factor, NunF, positively regulates the synthesis of nunamycin and nunapeptin in P. fluorescens In5 and that the nunF gene is upregulated by fungal-associated molecules. This study focused on further unravelling the complex regulation governing CLP synthesis in P. fluorescens In5. Promoter fusions were used to show that the specific activator NunF is dependent on the global regulator of secondary metabolism GacA and is regulated by fungal-associated molecules and low temperatures. In contrast, GacA is stimulated by plant signal molecules leading to the hypothesis that P. fluorescens is a hyphosphere-associated bacterium carrying transcription factor genes that respond to signals indicating the presence of fungi and oomycetes. Based on these findings, we present a model for how synthesis of nunamycin and nunapeptin is regulated by fungal- and oomycete-associated molecules.IMPORTANCE Cyclic lipopeptide (CLP) synthesis gene clusters in pseudomonads display a high degree of synteny, and the structures of the peptides synthesized are very similar. Accordingly, the genomic island encoding the synthesis of syringomycin and syringopeptin in P. syringae pv. syringae closely resembles that of P. fluorescens In5, which contains genes coding for synthesis of the antifungal and anti-oomycete peptides nunamycin and nunapeptin, respectively. However, the regulation of syringomycin and syringopeptin synthesis is different from that of nunamycin and nunapeptin synthesis. While CLP synthesis in the plant pathogen P. syringae pv. syringae is induced by plant signal molecules, such compounds do not significantly influence synthesis of nunamycin and nunapeptin in P. fluorescens In5. Instead, fungal-associated molecules positively regulate antifungal peptide synthesis in P. fluorescens In5, while the synthesis of the global regulator GacA in P. fluorescens In5 is positively regulated by plant signal molecules but not fungal-associated molecules.
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16
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Wu L, Wang Z, Guan Y, Huang X, Shi H, Liu Y, Zhang X. The (p)ppGpp-mediated stringent response regulatory system globally inhibits primary metabolism and activates secondary metabolism in Pseudomonas protegens H78. Appl Microbiol Biotechnol 2020; 104:3061-3079. [PMID: 32009198 DOI: 10.1007/s00253-020-10421-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/18/2020] [Accepted: 01/26/2020] [Indexed: 01/08/2023]
Abstract
Pseudomonas protegens H78 produces multiple secondary metabolites, including antibiotics and iron carriers. The guanosine pentaphosphate or tetraphosphate ((p)ppGpp)-mediated stringent response is utilized by bacteria to survive during nutritional starvation and other stresses. RelA/SpoT homologues are responsible for the biosynthesis and degradation of the alarmone (p)ppGpp. Here, we investigated the global effect of relA/spoT dual deletion on the transcriptomic profiles, physiology, and metabolism of P. protegens H78 grown to mid- to late log phase. Transcriptomic profiling revealed that relA/spoT deletion globally upregulated the expression of genes involved in DNA replication, transcription, and translation; amino acid metabolism; carbohydrate and energy metabolism; ion transport and metabolism; and secretion systems. Bacterial growth was partially increased, while the cell survival rate was significantly reduced by relA/spoT deletion in H78. The utilization of some nutritional elements (C, P, S, and N) was downregulated due to relA/spoT deletion. In contrast, relA/spoT mutation globally inhibited the expression of secondary metabolic gene clusters (plt, phl, prn, ofa, fit, pch, pvd, and has). Correspondingly, antibiotic and iron carrier biosynthesis, iron utilization, and antibiotic resistance were significantly downregulated by the relA/spoT mutation. This work highlights that the (p)ppGpp-mediated stringent response regulatory system plays an important role in inhibiting primary metabolism and activating secondary metabolism in P. protegens.
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Affiliation(s)
- Lingyu Wu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Zheng Wang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yejun Guan
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xianqing Huang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
| | - Huimin Shi
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Yujie Liu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
| | - Xuehong Zhang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China
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17
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Dutta S, Yu SM, Jeong SC, Lee YH. High-throughput analysis of genes involved in biocontrol performance of Pseudomonas fluorescens NBC275 against Gray mold. J Appl Microbiol 2019; 128:265-279. [PMID: 31574191 DOI: 10.1111/jam.14475] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 09/01/2019] [Accepted: 09/17/2019] [Indexed: 01/16/2023]
Abstract
AIMS Many physiological and microbial characteristics influence the biocontrol performance of the biological control agents (BCAs) in agricultural fields. To implement effective biocontrol, the contribution of specific genes, mechanisms and traits to the biocontrol performance of BCAs need to be characterized and explored in greater detail. METHODS AND RESULTS In this study, a transposon (Tn) mutant library using the BCA Pseudomonas fluorescens NBC275 (Pf275) was generated to explore genes and bacterial characteristics involved in antifungal activity and biocontrol performance. Among the Tn mutants, 205 strains showing variations in antifungal activity compared to wild-type (WT) were selected and further analysed for biocontrol efficacy against gray mold in pepper fruits. The genes involved in pyoverdine biosynthesis (pvdI and pvdD) and chitin-binding protein (gbpA) played essential roles in the antifungal activity and biocontrol capacity of Pf275. In addition, a mutation in phlD completely abolished the antifungal activity and significantly suppressed the biocontrol ability of the strain. Genes affecting antifungal activity of Pf275 significantly influenced swimming motility, which was identified as an important trait for the biocontrol ability of the bacterial strain. CONCLUSIONS Overall, our results suggest that antifungal compound production, siderophore biosynthesis and swimming motility synergistically contribute to Pf275 biocontrol performance. The utility of this library was demonstrated by identifying genes for antagonism and biocontrol ability in this BCA strain. The functional roles of many genes identified as contributing to antagonism and in vivo biocontrol activity require further study. SIGNIFICANCE AND IMPACT OF THIS STUDY Genes contributing to antifungal activity and biocontrol performance of P. fluorescens were identified and highlighted by Tn mutagenesis, which will give insight to improve the biocontrol performance of this BCA.
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Affiliation(s)
- S Dutta
- Division of Biotechnology, Chonbuk National University, Iksan-si, Jeollabuk-do, Republic of Korea
| | - S-M Yu
- Freshwater Bioresources Utilization Division, Nakdonggang National Institute of Biological Resources, Sangju-si, Gyeongsangbuk-do, Republic of Korea
| | - S C Jeong
- Freshwater Bioresources Utilization Division, Nakdonggang National Institute of Biological Resources, Sangju-si, Gyeongsangbuk-do, Republic of Korea
| | - Y H Lee
- Division of Biotechnology, Chonbuk National University, Iksan-si, Jeollabuk-do, Republic of Korea.,Advanced Institute of Environment and Bioscience, Plant Medical Research Center, and Institute of Bio-industry, Chonbuk National University, Ikansi-si, Jeollabuk-do, Republic of Korea
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18
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An integrated genomic regulatory network of virulence-related transcriptional factors in Pseudomonas aeruginosa. Nat Commun 2019; 10:2931. [PMID: 31270321 PMCID: PMC6610081 DOI: 10.1038/s41467-019-10778-w] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Accepted: 05/30/2019] [Indexed: 01/12/2023] Open
Abstract
The virulence of Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen, is regulated by many transcriptional factors (TFs) that control the expression of quorum sensing and protein secretion systems. Here, we report a genome-wide, network-based approach to dissect the crosstalk between 20 key virulence-related TFs. Using chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq), as well as RNA-seq, we identify 1200 TF-bound genes and 4775 differentially expressed genes. We experimentally validate 347 of these genes as functional target genes, and describe the regulatory relationships of the 20 TFs with their targets in a network that we call ‘Pseudomonas aeruginosa genomic regulatory network’ (PAGnet). Analysis of the network led to the identification of novel functions for two TFs (ExsA and GacA) in quorum sensing and nitrogen metabolism. Furthermore, we present an online platform and R package based on PAGnet to facilitate updating and user-customised analyses. The virulence of Pseudomonas aeruginosa is regulated by many transcriptional factors (TFs). Here, the authors study the crosstalk between 20 key virulence-related TFs, validate 347 functional target genes, and describe the regulatory relationships of the 20 TFs with their targets in a network that is available as an online platform.
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19
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Jahanshah G, Yan Q, Gerhardt H, Pataj Z, Lämmerhofer M, Pianet I, Josten M, Sahl HG, Silby MW, Loper JE, Gross H. Discovery of the Cyclic Lipopeptide Gacamide A by Genome Mining and Repair of the Defective GacA Regulator in Pseudomonas fluorescens Pf0-1. JOURNAL OF NATURAL PRODUCTS 2019; 82:301-308. [PMID: 30666877 DOI: 10.1021/acs.jnatprod.8b00747] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Genome mining of the Gram-negative bacterium Pseudomonas fluorescens Pf0-1 showed that the strain possesses a silent NRPS-based biosynthetic gene cluster encoding a new lipopeptide; its activation required the repair of the global regulator system. In this paper, we describe the genomics-driven discovery and characterization of the associated secondary metabolite gacamide A, a lipodepsipeptide that forms a new family of Pseudomonas lipopeptides. The compound has a moderate, narrow-spectrum antibiotic activity and facilitates bacterial surface motility.
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Affiliation(s)
- Gahzaleh Jahanshah
- Pharmaceutical Institute, Department of Pharmaceutical Biology , University of Tübingen , 72076 Tübingen , Germany
- German Centre for Infection Research (DZIF) , partner site Tübingen , 72076 Tübingen , Germany
| | - Qing Yan
- Department of Botany and Plant Pathology , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Heike Gerhardt
- Pharmaceutical Institute, Department of Pharmaceutical Analysis and Bioanalysis , University of Tübingen , 72076 Tübingen , Germany
- UMR 5060, IRAMAT-CRP2A, Esplanade des Antilles , F-33600 Pessac , France
| | - Zoltán Pataj
- Pharmaceutical Institute, Department of Pharmaceutical Analysis and Bioanalysis , University of Tübingen , 72076 Tübingen , Germany
- UMR 5060, IRAMAT-CRP2A, Esplanade des Antilles , F-33600 Pessac , France
| | - Michael Lämmerhofer
- Pharmaceutical Institute, Department of Pharmaceutical Analysis and Bioanalysis , University of Tübingen , 72076 Tübingen , Germany
- UMR 5060, IRAMAT-CRP2A, Esplanade des Antilles , F-33600 Pessac , France
| | - Isabelle Pianet
- CESAMO-ISM, UMR 5255, CNRS , Université Bordeaux I , 351 Cours de la Libération , F-33405 Talence , France
| | - Michaele Josten
- Institute for Medical Microbiology, Immunology and Parasitology (IMMIP), Pharmaceutical Microbiology Unit , University of Bonn , 53115 Bonn , Germany
- German Centre for Infection Research (DZIF) , partner site Bonn-Cologne , 53115 Bonn , Germany
| | - Hans-Georg Sahl
- Institute for Medical Microbiology, Immunology and Parasitology (IMMIP), Pharmaceutical Microbiology Unit , University of Bonn , 53115 Bonn , Germany
- German Centre for Infection Research (DZIF) , partner site Bonn-Cologne , 53115 Bonn , Germany
| | - Mark W Silby
- Department of Biology , University of Massachusetts Dartmouth , North Dartmouth , Massachusetts 02747 , United States
| | - Joyce E Loper
- Department of Botany and Plant Pathology , Oregon State University , Corvallis , Oregon 97331 , United States
- Agricultural Research Service , U.S. Department of Agriculture , Corvallis , Oregon 97331 , United States
| | - Harald Gross
- Pharmaceutical Institute, Department of Pharmaceutical Biology , University of Tübingen , 72076 Tübingen , Germany
- German Centre for Infection Research (DZIF) , partner site Tübingen , 72076 Tübingen , Germany
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20
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Liu Y, Shi H, Wang Z, Huang X, Zhang X. Pleiotropic control of antibiotic biosynthesis, flagellar operon expression, biofilm formation, and carbon source utilization by RpoN in Pseudomonas protegens H78. Appl Microbiol Biotechnol 2018; 102:9719-9730. [DOI: 10.1007/s00253-018-9282-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 07/23/2018] [Accepted: 07/26/2018] [Indexed: 02/04/2023]
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21
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Grenga L, Little RH, Malone JG. Quick change: post-transcriptional regulation in Pseudomonas. FEMS Microbiol Lett 2018; 364:3866594. [PMID: 28605536 PMCID: PMC5812540 DOI: 10.1093/femsle/fnx125] [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: 03/31/2017] [Accepted: 06/09/2017] [Indexed: 01/06/2023] Open
Abstract
Pseudomonas species have evolved dynamic and intricate regulatory networks to fine-tune gene expression, with complex regulation occurring at every stage in the processing of genetic information. This approach enables Pseudomonas to generate precise individual responses to the environment in order to improve their fitness and resource economy. The weak correlations we observe between RNA and protein abundance highlight the significant regulatory contribution of a series of intersecting post-transcriptional pathways, influencing mRNA stability, translational activity and ribosome function, to Pseudomonas environmental responses. This review examines our current understanding of three major post-transcriptional regulatory systems in Pseudomonas spp.; Gac/Rsm, Hfq and RimK, and presents an overview of new research frontiers, emerging genome-wide methodologies, and their potential for the study of global regulatory responses in Pseudomonas.
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Affiliation(s)
- Lucia Grenga
- John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.,University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Richard H Little
- John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - Jacob G Malone
- John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK.,University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
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22
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Mavridou DAI, Gonzalez D, Kim W, West SA, Foster KR. Bacteria Use Collective Behavior to Generate Diverse Combat Strategies. Curr Biol 2018; 28:345-355.e4. [PMID: 29395918 DOI: 10.1016/j.cub.2017.12.030] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 11/06/2017] [Accepted: 12/14/2017] [Indexed: 01/06/2023]
Abstract
Animals have evolved a wide diversity of aggressive behavior often based upon the careful monitoring of other individuals. Bacteria are also capable of aggression, with many species using toxins to kill or inhibit their competitors. Like animals, bacteria also have systems to monitor others during antagonistic encounters, but how this translates into behavior remains poorly understood. Here, we use colonies of Escherichia coli carrying colicin-encoding plasmids as a model for studying antagonistic behavior. We show that in the absence of threat, dispersed cells with low reproductive value produce colicin toxins spontaneously, generating efficient pre-emptive attacks. Cells can also respond conditionally to toxins released by clonemates via autoinduction or other genotypes via competition sensing. The strength of both pre-emptive and responsive attacks varies widely between strains. We demonstrate that this variability occurs easily through mutation by rationally engineering strains to recapitulate the diversity in naturally occurring strategies. Finally, we discover that strains that can detect both competitors and clonemates are capable of massive coordinated attacks on competing colonies. This collective behavior protects established colonies from competitors, mirroring the evolution of alarm calling in the animal world.
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Affiliation(s)
- Despoina A I Mavridou
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK; MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, Kensington, London SW7 2DD, UK
| | - Diego Gonzalez
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK
| | - Wook Kim
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK
| | - Stuart A West
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK
| | - Kevin R Foster
- Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Calleva Research Centre for Evolution and Human Sciences, Magdalen College, Oxford OX1 4AU, UK.
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23
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Secondary Metabolism and Interspecific Competition Affect Accumulation of Spontaneous Mutants in the GacS-GacA Regulatory System in Pseudomonas protegens. mBio 2018; 9:mBio.01845-17. [PMID: 29339425 PMCID: PMC5770548 DOI: 10.1128/mbio.01845-17] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Secondary metabolites are synthesized by many microorganisms and provide a fitness benefit in the presence of competitors and predators. Secondary metabolism also can be costly, as it shunts energy and intermediates from primary metabolism. In Pseudomonas spp., secondary metabolism is controlled by the GacS-GacA global regulatory system. Intriguingly, spontaneous mutations in gacS or gacA (Gac− mutants) are commonly observed in laboratory cultures. Here we investigated the role of secondary metabolism in the accumulation of Gac− mutants in Pseudomonas protegens strain Pf-5. Our results showed that secondary metabolism, specifically biosynthesis of the antimicrobial compound pyoluteorin, contributes significantly to the accumulation of Gac− mutants. Pyoluteorin biosynthesis, which poses a metabolic burden on the producer cells, but not pyoluteorin itself, leads to the accumulation of the spontaneous mutants. Interspecific competition also influenced the accumulation of the Gac− mutants: a reduced proportion of Gac− mutants accumulated when P. protegens Pf-5 was cocultured with Bacillus subtilis than in pure cultures of strain Pf-5. Overall, our study associated a fitness trade-off with secondary metabolism, with metabolic costs versus competitive benefits of production influencing the evolution of P. protegens, assessed by the accumulation of Gac− mutants. Many microorganisms produce antibiotics, which contribute to ecologic fitness in natural environments where microbes constantly compete for resources with other organisms. However, biosynthesis of antibiotics is costly due to the metabolic burdens of the antibiotic-producing microorganism. Our results provide an example of the fitness trade-off associated with antibiotic production. Under noncompetitive conditions, antibiotic biosynthesis led to accumulation of spontaneous mutants lacking a master regulator of antibiotic production. However, relatively few of these spontaneous mutants accumulated when a competitor was present. Results from this work provide information on the evolution of antibiotic biosynthesis and provide a framework for their discovery and regulation.
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Sobrero PM, Muzlera A, Frescura J, Jofré E, Valverde C. A matter of hierarchy: activation of orfamide production by the post-transcriptional Gac-Rsm cascade of Pseudomonas protegens CHA0 through expression upregulation of the two dedicated transcriptional regulators. ENVIRONMENTAL MICROBIOLOGY REPORTS 2017; 9:599-611. [PMID: 28703431 DOI: 10.1111/1758-2229.12566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Accepted: 06/21/2017] [Indexed: 06/07/2023]
Abstract
In this work, we surveyed the genome of P. protegens CHA0 in order to identify novel mRNAs possibly under the control of the Gac-Rsm cascade that might, for their part, serve to elucidate as-yet-unknown functions involved in the biocontrol of plant pathogens and/or in cellular processes required for fitness in natural environments. In view of the experimental evidence from former studies on the Gac-Rsm cascade, we developed a computational screen supported by a combination of sequence, structural and evolutionary constraints that led to a dataset of 43 potential novel mRNA targets. We then confirmed several mRNA targets experimentally and next focused on two of the respective genes that are physically linked to the orfamide biosynthetic gene cluster and whose predicted open-reading frames resembled cognate LuxR-type transcriptional regulators of cyclic lipopeptide clusters in related pseudomonads. In this report, we demonstrate that in strain CHA0, orfamide production is stringently dependent on a functional Gac-Rsm cascade and that both mRNAs encoding transcriptional regulatory proteins are under direct translational control of the RsmA/E proteins. Our results have thus revealed a hierarchical control over the expression of orfamide biosynthetic genes with the final transcriptional control subordinated to the global Gac-Rsm post-transcriptional regulatory system.
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Affiliation(s)
- Patricio Martín Sobrero
- CONICET, Departamento de Ciencia y Tecnología, Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo. Roque Sáenz Peña 352, Bernal B1876BXD, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Andrés Muzlera
- CONICET, Departamento de Ciencia y Tecnología, Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo. Roque Sáenz Peña 352, Bernal B1876BXD, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Julieta Frescura
- CONICET, Departamento de Ciencia y Tecnología, Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo. Roque Sáenz Peña 352, Bernal B1876BXD, Universidad Nacional de Quilmes, Buenos Aires, Argentina
| | - Edgardo Jofré
- CONICET, Facultad de Ciencias Exactas Físico-Químicas y Naturales, Departmento de Ciencias Naturales. Ruta Nacional 36 Km 601, Universidad Nacional de Río Cuarto, 5800 Río Cuarto, Córdoba, Argentina
| | - Claudio Valverde
- CONICET, Departamento de Ciencia y Tecnología, Laboratorio de Bioquímica, Microbiología e Interacciones Biológicas en el Suelo. Roque Sáenz Peña 352, Bernal B1876BXD, Universidad Nacional de Quilmes, Buenos Aires, Argentina
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Wang Z, Huang X, Liu Y, Yang G, Liu Y, Zhang X. GacS/GacA activates pyoluteorin biosynthesis through Gac/Rsm-RsmE cascade and RsmA/RsmE-driven feedback loop inPseudomonas protegensH78. Mol Microbiol 2017; 105:968-985. [DOI: 10.1111/mmi.13749] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/11/2017] [Indexed: 12/16/2022]
Affiliation(s)
- Zheng Wang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences & Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Xianqing Huang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences & Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Yujie Liu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences & Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Guohuan Yang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences & Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Yang Liu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences & Biotechnology; Shanghai Jiao Tong University; Shanghai China
| | - Xuehong Zhang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences & Biotechnology; Shanghai Jiao Tong University; Shanghai China
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Reboud E, Elsen S, Bouillot S, Golovkine G, Basso P, Jeannot K, Attrée I, Huber P. Phenotype and toxicity of the recently discovered exlA-positive Pseudomonas aeruginosa strains collected worldwide. Environ Microbiol 2016; 18:3425-3439. [PMID: 26914644 DOI: 10.1111/1462-2920.13262] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 02/11/2016] [Indexed: 11/30/2022]
Abstract
We recently identified a hypervirulent strain of Pseudomonas aeruginosa, differing significantly from the classical strains in that it lacks the type 3 secretion system (T3SS), a major determinant of P. aeruginosa virulence. This new strain secretes a novel toxin, called ExlA, which induces plasma membrane rupture in host cells. For this study, we collected 18 other exlA-positive T3SS-negative strains, analyzed their main virulence factors and tested their toxicity in various models. Phylogenetic analysis revealed two groups. The strains were isolated on five continents from patients with various pathologies or in the environment. Their proteolytic activity and their motion abilities were highly different, as well as their capacity to infect epithelial, endothelial, fibroblastic and immune cells, which correlated directly with ExlA secretion levels. In contrast, their toxicity towards human erythrocytes was limited. Some strains were hypervirulent in a mouse pneumonia model and others on chicory leaves. We conclude that (i) exlA-positive strains can colonize different habitats and may induce various infection types, (ii) the strains secreting significant amounts of ExlA are cytotoxic for most cell types but are poorly hemolytic, (iii) toxicity in planta does not correlate with ExlA secretion.
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Affiliation(s)
- Emeline Reboud
- Univ. Grenoble Alpes, 38000, Grenoble, France
- CNRS, ERL5261, 38000, Grenoble, France
- CEA, iRTSV-BCI, 38000, Grenoble, France
- INSERM, U1036, 38000, Grenoble, France
| | - Sylvie Elsen
- Univ. Grenoble Alpes, 38000, Grenoble, France
- CNRS, ERL5261, 38000, Grenoble, France
- CEA, iRTSV-BCI, 38000, Grenoble, France
- INSERM, U1036, 38000, Grenoble, France
| | - Stéphanie Bouillot
- Univ. Grenoble Alpes, 38000, Grenoble, France
- CNRS, ERL5261, 38000, Grenoble, France
- CEA, iRTSV-BCI, 38000, Grenoble, France
- INSERM, U1036, 38000, Grenoble, France
| | - Guillaume Golovkine
- Univ. Grenoble Alpes, 38000, Grenoble, France
- CNRS, ERL5261, 38000, Grenoble, France
- CEA, iRTSV-BCI, 38000, Grenoble, France
- INSERM, U1036, 38000, Grenoble, France
| | - Pauline Basso
- Univ. Grenoble Alpes, 38000, Grenoble, France
- CNRS, ERL5261, 38000, Grenoble, France
- CEA, iRTSV-BCI, 38000, Grenoble, France
- INSERM, U1036, 38000, Grenoble, France
| | - Katy Jeannot
- Hôpital Universitaire de Besançon, 25030, Besançon, France
| | - Ina Attrée
- Univ. Grenoble Alpes, 38000, Grenoble, France
- CNRS, ERL5261, 38000, Grenoble, France
- CEA, iRTSV-BCI, 38000, Grenoble, France
- INSERM, U1036, 38000, Grenoble, France
| | - Philippe Huber
- Univ. Grenoble Alpes, 38000, Grenoble, France.
- CNRS, ERL5261, 38000, Grenoble, France.
- CEA, iRTSV-BCI, 38000, Grenoble, France.
- INSERM, U1036, 38000, Grenoble, France.
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Ramos-González MI, Travieso ML, Soriano MI, Matilla MA, Huertas-Rosales Ó, Barrientos-Moreno L, Tagua VG, Espinosa-Urgel M. Genetic Dissection of the Regulatory Network Associated with High c-di-GMP Levels in Pseudomonas putida KT2440. Front Microbiol 2016; 7:1093. [PMID: 27489550 PMCID: PMC4951495 DOI: 10.3389/fmicb.2016.01093] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 06/30/2016] [Indexed: 11/24/2022] Open
Abstract
Most bacteria grow in nature forming multicellular structures named biofilms. The bacterial second messenger cyclic diguanosine monophosphate (c-di-GMP) is a key player in the regulation of the transition from planktonic to sessile lifestyles and this regulation is crucial in the development of biofilms. In Pseudomonas putida KT2440, Rup4959, a multidomain response regulator with diguanylate cyclase activity, when overexpressed causes an increment in the intracellular levels of c-di-GMP that gives rise to a pleiotropic phenotype consisting of increased biofilm formation and crinkly colony morphology. In a broad genomic screen we have isolated mutant derivatives that lose the crinkly morphology, designed as cfc (crinkle free colony). A total of 19 different genes have been identified as being related with the emergence of the cfc phenotype either because the expression or functionality of Rup4959 is compromised, or due to a lack of transduction of the c-di-GMP signal to downstream elements involved in the acquisition of the phenotype. Discernment between these possibilities was investigated by using a c-di-GMP biosensor and by HPLC-MS quantification of the second messenger. Interestingly five of the identified genes encode proteins with AAA+ ATPase domain. Among the bacterial determinants found in this screen are the global transcriptional regulators GacA, AlgU and FleQ and two enzymes involved in the arginine biosynthesis pathway. We present evidences that this pathway seems to be an important element to both the availability of the free pool of the second messenger c-di-GMP and to its further transduction as a signal for biosynthesis of biopolimers. In addition we have identified an uncharacterized hybrid sensor histidine kinase whose phosphoaceptor conserved histidine residue has been shown in this work to be required for in vivo activation of the orphan response regulator Rup4959, which suggests these two elements constitute a two-component phosphorelay system.
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Affiliation(s)
- María Isabel Ramos-González
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - María L Travieso
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - María I Soriano
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Miguel A Matilla
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Óscar Huertas-Rosales
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Laura Barrientos-Moreno
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Víctor G Tagua
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
| | - Manuel Espinosa-Urgel
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas Granada, Spain
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28
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Chambonnier G, Roux L, Redelberger D, Fadel F, Filloux A, Sivaneson M, de Bentzmann S, Bordi C. The Hybrid Histidine Kinase LadS Forms a Multicomponent Signal Transduction System with the GacS/GacA Two-Component System in Pseudomonas aeruginosa. PLoS Genet 2016; 12:e1006032. [PMID: 27176226 PMCID: PMC4866733 DOI: 10.1371/journal.pgen.1006032] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 04/17/2016] [Indexed: 12/16/2022] Open
Abstract
In response to environmental changes, Pseudomonas aeruginosa is able to switch from a planktonic (free swimming) to a sessile (biofilm) lifestyle. The two-component system (TCS) GacS/GacA activates the production of two small non-coding RNAs, RsmY and RsmZ, but four histidine kinases (HKs), RetS, GacS, LadS and PA1611, are instrumental in this process. RetS hybrid HK blocks GacS unorthodox HK autophosphorylation through the formation of a heterodimer. PA1611 hybrid HK, which is structurally related to GacS, interacts with RetS in P. aeruginosa in a very similar manner to GacS. LadS hybrid HK phenotypically antagonizes the function of RetS by a mechanism that has never been investigated. The four sensors are found in most Pseudomonas species but their characteristics and mode of signaling may differ from one species to another. Here, we demonstrated in P. aeruginosa that LadS controls both rsmY and rsmZ gene expression and that this regulation occurs through the GacS/GacA TCS. We additionally evidenced that in contrast to RetS, LadS signals through GacS/GacA without forming heterodimers, either with GacS or with RetS. Instead, we demonstrated that LadS is involved in a genuine phosphorelay, which requires both transmitter and receiver LadS domains. LadS signaling ultimately requires the alternative histidine-phosphotransfer domain of GacS, which is here used as an Hpt relay by the hybrid kinase. LadS HK thus forms, with the GacS/GacA TCS, a multicomponent signal transduction system with an original phosphorelay cascade, i.e. H1LadS→D1LadS→H2GacS→D2GacA. This highlights an original strategy in which a unique output, i.e. the modulation of sRNA levels, is controlled by a complex multi-sensing network to fine-tune an adapted biofilm and virulence response.
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Affiliation(s)
- Gaël Chambonnier
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
| | - Lorène Roux
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
| | - David Redelberger
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
| | - Firas Fadel
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
- Aix Marseille Université, CNRS, AFMB UMR 7257, 13288, Marseille, France
| | - Alain Filloux
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
| | - Melissa Sivaneson
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
| | - Sophie de Bentzmann
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
| | - Christophe Bordi
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS UMR7255, Marseille, France
- * E-mail:
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29
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Biotechnological potential of a rhizosphere Pseudomonas aeruginosa strain producing phenazine-1-carboxylic acid and phenazine-1-carboxamide. World J Microbiol Biotechnol 2016; 32:50. [DOI: 10.1007/s11274-015-1987-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 11/26/2015] [Indexed: 12/31/2022]
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30
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Mitri S, Foster KR. Pleiotropy and the low cost of individual traits promote cooperation. Evolution 2016; 70:488-94. [DOI: 10.1111/evo.12851] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 12/08/2015] [Accepted: 12/16/2015] [Indexed: 12/17/2022]
Affiliation(s)
- Sara Mitri
- Department of Fundamental Microbiology; University of Lausanne; Lausanne Switzerland
| | - Kevin R. Foster
- Department of Zoology; University of Oxford; Oxford UK
- Oxford Centre for Integrative Systems Biology; University of Oxford; Oxford UK
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31
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Mercy C, Ize B, Salcedo SP, de Bentzmann S, Bigot S. Functional Characterization of Pseudomonas Contact Dependent Growth Inhibition (CDI) Systems. PLoS One 2016; 11:e0147435. [PMID: 26808644 PMCID: PMC4725963 DOI: 10.1371/journal.pone.0147435] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/04/2016] [Indexed: 11/18/2022] Open
Abstract
Contact-dependent inhibition (CDI) toxins, delivered into the cytoplasm of target bacterial cells, confer to host strain a significant competitive advantage. Upon cell contact, the toxic C-terminal region of surface-exposed CdiA protein (CdiA-CT) inhibits the growth of CDI- bacteria. CDI+ cells express a specific immunity protein, CdiI, which protects from autoinhibition by blocking the activity of cognate CdiA-CT. CdiA-CT are separated from the rest of the protein by conserved peptide motifs falling into two distinct classes, the “E. coli”- and “Burkholderia-type”. CDI systems have been described in numerous species except in Pseudomonadaceae. In this study, we identified functional toxin/immunity genes linked to CDI systems in the Pseudomonas genus, which extend beyond the conventional CDI classes by the variability of the peptide motif that delimits the polymorphic CdiA-CT domain. Using P. aeruginosa PAO1 as a model, we identified the translational repressor RsmA as a negative regulator of CDI systems. Our data further suggest that under conditions of expression, P. aeruginosa CDI systems are implicated in adhesion and biofilm formation and provide an advantage in competition assays. All together our data imply that CDI systems could play an important role in niche adaptation of Pseudomonadaceae.
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Affiliation(s)
- Chryslène Mercy
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255, Université Aix Marseille, Marseille, France
- Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France
| | - Bérengère Ize
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255, Université Aix Marseille, Marseille, France
| | - Suzana P. Salcedo
- Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France
| | - Sophie de Bentzmann
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255, Université Aix Marseille, Marseille, France
| | - Sarah Bigot
- Laboratoire d’Ingénierie des Systèmes Macromoléculaires, CNRS UMR7255, Université Aix Marseille, Marseille, France
- Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France
- * E-mail:
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32
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Regulation of GacA in Pseudomonas chlororaphis Strains Shows a Niche Specificity. PLoS One 2015; 10:e0137553. [PMID: 26379125 PMCID: PMC4574860 DOI: 10.1371/journal.pone.0137553] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2015] [Accepted: 08/19/2015] [Indexed: 01/26/2023] Open
Abstract
The GacS/GacA two-component system plays a central role in the regulation of a broad range of biological functions in many bacteria. In the biocontrol organism Pseudomonas chlororaphis, the Gac system has been shown to positively control quorum sensing, biofilm formation, and phenazine production, but has an overall negative impact on motility. These studies have been performed with strains originated from the rhizosphere predominantly. To investigate the level of conservation between the GacA regulation of biocontrol-related traits in P. chlororaphis isolates from different habitats, the studies presented here focused on the endophytic isolate G5 of P. chlororaphis subsp. aurantiaca. A gacA mutant deficient in the production of N-acylhomoserine lactones (AHLs) and phenazine was isolated through transposon mutagenesis. Further phenotypic characterization revealed that in strain G5, similar to other P. chlororaphis strains, a gacA mutation caused inability to produce biocontrol factors such as phenazine, HCN and proteases responsible for antifungal activity, but overproduced siderophores. LC-MS/MS analysis revealed that AHL production was also practically abolished in this mutant. However, the wild type exhibited an extremely diverse AHL pattern which has never been identified in P. chlororaphis. In contrast to other isolates of this organism, GacA in strain G5 was shown to negatively regulate biofilm formation and oxidative stress response whilst positively regulating cell motility and biosynthesis of indole-3-acetic acid (IAA). To gain a better understanding of the overall impact of GacA in G5, a comparative proteomic analysis was performed revealing that, in addition to some of the traits like phenazine mentioned above, GacA also negatively regulated lipopolysaccharide (LPS) and trehalose biosynthesis whilst having a positive impact on energy metabolism, an effect not previously described in P. chlororaphis. Consequently, GacA regulation shows a differential strain dependency which is likely to be in line with their niche of origin.
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Meisel JD, Panda O, Mahanti P, Schroeder FC, Kim DH. Chemosensation of bacterial secondary metabolites modulates neuroendocrine signaling and behavior of C. elegans. Cell 2015; 159:267-80. [PMID: 25303524 DOI: 10.1016/j.cell.2014.09.011] [Citation(s) in RCA: 180] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 07/03/2014] [Accepted: 09/03/2014] [Indexed: 11/30/2022]
Abstract
Discrimination between pathogenic and beneficial microbes is essential for host organism immunity and homeostasis. Here, we show that chemosensory detection of two secondary metabolites produced by Pseudomonas aeruginosa modulates a neuroendocrine signaling pathway that promotes avoidance behavior in the simple animal host Caenorhabditis elegans. Secondary metabolites phenazine-1-carboxamide and pyochelin activate a G-protein-signaling pathway in the ASJ chemosensory neuron pair that induces expression of the neuromodulator DAF-7/TGF-β. DAF-7, in turn, activates a canonical TGF-β signaling pathway in adjacent interneurons to modulate aerotaxis behavior and promote avoidance of pathogenic P. aeruginosa. Our data provide a chemical, genetic, and neuronal basis for how the behavior and physiology of a simple animal host can be modified by the microbial environment and suggest that secondary metabolites produced by microbes may provide environmental cues that contribute to pathogen recognition and host survival.
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Affiliation(s)
- Joshua D Meisel
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Oishika Panda
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Parag Mahanti
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Frank C Schroeder
- Boyce Thompson Institute and Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Dennis H Kim
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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34
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Chieng S, Mohamed R, Nathan S. Transcriptome analysis of Burkholderia pseudomallei T6SS identifies Hcp1 as a potential serodiagnostic marker. Microb Pathog 2015; 79:47-56. [PMID: 25616255 DOI: 10.1016/j.micpath.2015.01.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Revised: 01/16/2015] [Accepted: 01/19/2015] [Indexed: 10/24/2022]
Abstract
Burkholderia pseudomallei, the causative agent of melioidosis, is able to survive extreme environments and utilizes various virulence factors for survival and pathogenicity. To compete and survive within these different ecological niches, B. pseudomallei has evolved specialized pathways, including the Type VI secretion systems (T6SSs), that have a role in pathogenesis as well as interbacterial interactions. We examined the expression profile of B. pseudomallei T6SS six gene clusters during infection of U937 macrophage cells. T6SS-5 was robustly transcribed while the other five clusters were not significantly regulated proposing the utility of T6SS-5 as a potential biomarker of exposure to B. pseudomallei. Transcription of T6SS regulators VirAG and BprB was also not significant during infection when compared to bacteria grown in culture. Guided by these findings, three highly expressed T6SS genes, tssJ-4, hcp1 and tssE-5, were expressed as recombinant proteins and screened against melioidosis patient sera by western analysis and ELISA. Only Hcp1 was reactive by both types of analysis. The recombinant Hcp1 protein was further evaluated against a cohort of melioidosis patients (n = 32) and non-melioidosis individuals (n = 20) sera and the data clearly indicates a higher sensitivity (93.7%) and specificity (100%) for Hcp1 compared to bacterial lysate. The detection of anti-Hcp1 antibodies in patients' sera indicating the presence of B. pseudomallei highlights the potential of Hcp1 to be further developed as a serodiagnostic marker for melioidosis.
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Affiliation(s)
- Sylvia Chieng
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia
| | - Rahmah Mohamed
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia
| | - Sheila Nathan
- School of Biosciences and Biotechnology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia.
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Dispersed cells represent a distinct stage in the transition from bacterial biofilm to planktonic lifestyles. Nat Commun 2014; 5:4462. [PMID: 25042103 DOI: 10.1038/ncomms5462] [Citation(s) in RCA: 246] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 06/20/2014] [Indexed: 01/21/2023] Open
Abstract
Bacteria assume distinct lifestyles during the planktonic and biofilm modes of growth. Increased levels of the intracellular messenger c-di-GMP determine the transition from planktonic to biofilm growth, while a reduction causes biofilm dispersal. It is generally assumed that cells dispersed from biofilms immediately go into the planktonic growth phase. Here we use single-nucleotide resolution transcriptomic analysis to show that the physiology of dispersed cells from Pseudomonas aeruginosa biofilms is highly different from those of planktonic and biofilm cells. In dispersed cells, the expression of the small regulatory RNAs RsmY and RsmZ is downregulated, whereas secretion genes are induced. Dispersed cells are highly virulent against macrophages and Caenorhabditis elegans compared with planktonic cells. In addition, they are highly sensitive towards iron stress, and the combination of a biofilm-dispersing agent, an iron chelator and tobramycin efficiently reduces the survival of the dispersed cells.
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Zhao K, Li Y, Yue B, Wu M. Genes as early responders regulate quorum-sensing and control bacterial cooperation in Pseudomonas aeruginosa. PLoS One 2014; 9:e101887. [PMID: 25006971 PMCID: PMC4090235 DOI: 10.1371/journal.pone.0101887] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 06/12/2014] [Indexed: 11/19/2022] Open
Abstract
Quorum-sensing (QS) allows bacterial communication to coordinate the production of extracellular products essential for population fitness at higher cell densities. It has been generally accepted that a significant time duration is required to reach appropriate cell density to activate the relevant quiescent genes encoding these costly but beneficial public goods. Which regulatory genes are involved and how these genes control bacterial communication at the early phases are largely un-explored. By determining time-dependent expression of QS-related genes of the opportunistic pathogen Pseudomonas aerugionsa, we show that the induction of social cooperation could be critically influenced by environmental factors to optimize the density of population. In particular, small regulatory RNAs (RsmY and RsmZ) serving as early responders, can promote the expression of dependent genes (e.g. lasR) to boost the synthesis of intracellular enzymes and coordinate instant cooperative behavior in bacterial cells. These early responders, acting as a rheostat to finely modulate bacterial cooperation, which may be quickly activated under environment threats, but peter off when critical QS dependent genes are fully functional for cooperation. Our findings suggest that RsmY and RsmZ critically control the timing and levels of public goods production, which may have implications in sociomicrobiology and infection control.
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Affiliation(s)
- Kelei Zhao
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, United States of America
- Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China
| | - Yi Li
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, United States of America
| | - Bisong Yue
- Key Laboratory of Bio-resources and Eco-environment, Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, Sichuan, China
| | - Min Wu
- Department of Basic Sciences, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota, United States of America
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Ghequire MGK, De Mot R. Ribosomally encoded antibacterial proteins and peptides from Pseudomonas. FEMS Microbiol Rev 2014; 38:523-68. [PMID: 24923764 DOI: 10.1111/1574-6976.12079] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/05/2014] [Accepted: 05/16/2014] [Indexed: 12/26/2022] Open
Abstract
Members of the Pseudomonas genus produce diverse secondary metabolites affecting other bacteria, fungi or predating nematodes and protozoa but are also equipped with the capacity to secrete different types of ribosomally encoded toxic peptides and proteins, ranging from small microcins to large tailocins. Studies with the human pathogen Pseudomonas aeruginosa have revealed that effector proteins of type VI secretion systems are part of the antibacterial armamentarium deployed by pseudomonads. A novel class of antibacterial proteins with structural similarity to plant lectins was discovered by studying antagonism among plant-associated Pseudomonas strains. A genomic perspective on pseudomonad bacteriocinogeny shows that the modular architecture of S pyocins of P. aeruginosa is retained in a large diversified group of bacteriocins, most of which target DNA or RNA. Similar modularity is present in as yet poorly characterized Rhs (recombination hot spot) proteins and CDI (contact-dependent inhibition) proteins. Well-delimited domains for receptor recognition or cytotoxicity enable the design of chimeric toxins with novel functionalities, which has been applied successfully for S and R pyocins. Little is known regarding how these antibacterials are released and ultimately reach their targets. Other remaining issues concern the identification of environmental triggers activating these systems and assessment of their ecological impact in niches populated by pseudomonads.
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The two-component regulators GacS and GacA positively regulate a nonfluorescent siderophore through the Gac/Rsm signaling cascade in high-siderophore-yielding Pseudomonas sp. strain HYS. J Bacteriol 2014; 196:3259-70. [PMID: 24982309 DOI: 10.1128/jb.01756-14] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Siderophores, which are produced to overcome iron deficiency, are believed to be closely related to the adaptability of bacteria. The high-siderophore-yielding Pseudomonas sp. strain HYS simultaneously secretes the fluorescent siderophore pyoverdine and another nonfluorescent siderophore that is a major contributor to the high siderophore yield. Transposon mutagenesis revealed siderophore-related genes, including the two-component regulators GacS/GacA and a special cluster containing four open reading frames (the nfs cluster). Deletion mutations of these genes abolished nonfluorescent-siderophore production, and expression of the nfs cluster depended on gacA, indicating that gacS-gacA may control the nonfluorescent siderophore through regulation of the nfs cluster. Furthermore, regulation of the nonfluorescent siderophore by GacS/GacA involved the Gac/Rsm pathway. In contrast, inactivation of GacS/GacA led to upregulation of the fluorescent pyoverdine. The two siderophores were secreted under different iron conditions, probably because of differential effects of GacS/GacA. The global GacS/GacA regulatory system may control iron uptake by modulating siderophore production and may enable bacteria to adapt to changing iron environments.
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Salje J. A single-cell imaging screen reveals multiple effects of secreted small molecules on bacteria. Microbiologyopen 2014; 3:426-36. [PMID: 24910069 PMCID: PMC4287172 DOI: 10.1002/mbo3.176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 03/25/2014] [Accepted: 04/04/2014] [Indexed: 12/14/2022] Open
Abstract
Bacteria cells exist in close proximity to other cells of both the same and different species. Bacteria secrete a large number of different chemical species, and the local concentrations of these compounds at the surfaces of nearby cells may reach very high levels. It is fascinating to imagine how individual cells might sense and respond to the complex mix of signals at their surface. However, it is difficult to measure exactly what the local environmental composition looks like, or what the effects of individual compounds on nearby cells are. Here, an electron microscopy imaging screen was designed that would detect morphological changes induced by secreted small molecules. This differs from conventional approaches by detecting structural changes in individual cells rather than gene expression or growth rate changes at the population level. For example, one of the changes detected here was an increase in outer membrane vesicle production, which does not necessarily correspond to a change in gene expression. This initial study focussed on Pseudomonas aeruginosa, Escherichia coli, and Burkholderia dolosa, and revealed an intriguing range of effects of secreted small molecules on cells both within and between species.
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Affiliation(s)
- Jeanne Salje
- Harvard Medical School, 200 Longwood Avenue, Boston, Massachusetts, 02115
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