151
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Burkholderia gladioli CGB10: A Novel Strain Biocontrolling the Sugarcane Smut Disease. Microorganisms 2020; 8:microorganisms8121943. [PMID: 33297590 PMCID: PMC7762381 DOI: 10.3390/microorganisms8121943] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 11/27/2020] [Accepted: 12/04/2020] [Indexed: 12/14/2022] Open
Abstract
In this study, we isolated an endophytic Burkholderia gladioli strain, named CGB10, from sugarcane leaves. B. gladioli CGB10 displayed strong inhibitory activity against filamentous growth of fungal pathogens, one of which is Sporisorium scitamineum that causes sugarcane smut, a major disease affecting the quality and production of sugarcane in tropical and subtropical regions. CGB10 could effectively suppress sugarcane smut under field conditions, without itself causing any obvious damage or disease, thus underscoring a great potential as a biocontrol agent (BCA) for the management of sugarcane smut. A toxoflavin biosynthesis and transport gene cluster potentially responsible for such antifungal activity was identified in the CGB10 genome. Additionally, a quorum-sensing gene cluster was identified too and compared with two close Burkholderia species, thus supporting an overall connection to the regulation of toxoflavin synthesis therein. Overall, this work describes the in vitro and field Sporisorium scitamineum biocontrol by a new B. gladioli strain, and reports genes and molecular mechanisms potentially involved.
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152
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Steinbach G, Crisan C, Ng SL, Hammer BK, Yunker PJ. Accumulation of dead cells from contact killing facilitates coexistence in bacterial biofilms. J R Soc Interface 2020; 17:20200486. [PMID: 33292099 PMCID: PMC7811593 DOI: 10.1098/rsif.2020.0486] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 11/12/2020] [Indexed: 02/06/2023] Open
Abstract
Bacterial communities are governed by a wide variety of social interactions, some of which are antagonistic with potential significance for bacterial warfare. Several antagonistic mechanisms, such as killing via the type VI secretion system (T6SS), require killer cells to directly contact target cells. The T6SS is hypothesized to be a highly potent weapon, capable of facilitating the invasion and defence of bacterial populations. However, we find that the efficacy of contact killing is severely limited by the material consequences of cell death. Through experiments with Vibrio cholerae strains that kill via the T6SS, we show that dead cell debris quickly accumulates at the interface that forms between competing strains, preventing physical contact and thus preventing killing. While previous experiments have shown that T6SS killing can reduce a population of target cells by as much as 106-fold, we find that, as a result of the formation of dead cell debris barriers, the impact of contact killing depends sensitively on the initial concentration of killer cells. Killer cells are incapable of invading or eliminating competitors on a community level. Instead, bacterial warfare itself can facilitate coexistence between nominally antagonistic strains. While a variety of defensive strategies against microbial warfare exist, the material consequences of cell death provide target cells with their first line of defence.
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Affiliation(s)
- Gabi Steinbach
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
| | - Cristian Crisan
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Siu Lung Ng
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Brian K. Hammer
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Peter J. Yunker
- School of Physics, Georgia Institute of Technology, Atlanta, GA, USA
- Center for Microbial Dynamics and Infection, Georgia Institute of Technology, Atlanta, GA, USA
- Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA
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153
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Lin HH, Filloux A, Lai EM. Role of Recipient Susceptibility Factors During Contact-Dependent Interbacterial Competition. Front Microbiol 2020; 11:603652. [PMID: 33281802 PMCID: PMC7690452 DOI: 10.3389/fmicb.2020.603652] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 10/13/2020] [Indexed: 11/13/2022] Open
Abstract
Bacteria evolved multiple strategies to survive and develop optimal fitness in their ecological niche. They deployed protein secretion systems for robust and efficient delivery of antibacterial toxins into their target cells, therefore inhibiting their growth or killing them. To maximize antagonism, recipient factors on target cells can be recognized or hijacked to enhance the entry or toxicity of these toxins. To date, knowledge regarding recipient susceptibility (RS) factors and their mode of action is mostly originating from studies on the type Vb secretion system that is also known as the contact-dependent inhibition (CDI) system. Yet, recent studies on the type VI secretion system (T6SS), and the CDI by glycine-zipper protein (Cdz) system, also reported the emerging roles of RS factors in interbacterial competition. Here, we review these RS factors and their mechanistic impact in increasing susceptibility of recipient cells in response to CDI, T6SS, and Cdz. Past and future strategies for identifying novel RS factors are also discussed, which will help in understanding the interplay between attacker and prey upon secretion system-dependent competition. Understanding these mechanisms would also provide insights for developing novel antibacterial strategies to antagonize aggressive bacteria-killing pathogens.
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Affiliation(s)
- Hsiao-Han Lin
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
| | - Alain Filloux
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Erh-Min Lai
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan
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154
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Snelders NC, Rovenich H, Petti GC, Rocafort M, van den Berg GCM, Vorholt JA, Mesters JR, Seidl MF, Nijland R, Thomma BPHJ. Microbiome manipulation by a soil-borne fungal plant pathogen using effector proteins. NATURE PLANTS 2020; 6:1365-1374. [PMID: 33139860 DOI: 10.1038/s41477-020-00799-5] [Citation(s) in RCA: 89] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 09/29/2020] [Indexed: 05/23/2023]
Abstract
During colonization of their hosts, pathogens secrete effector proteins to promote disease development through various mechanisms. Increasing evidence shows that the host microbiome plays a crucial role in health, and that hosts actively shape their microbiomes to suppress disease. We proposed that pathogens evolved to manipulate host microbiomes to their advantage in turn. Here, we show that the previously identified virulence effector VdAve1, secreted by the fungal plant pathogen Verticillium dahliae, displays antimicrobial activity and facilitates colonization of tomato and cotton through the manipulation of their microbiomes by suppressing antagonistic bacteria. Moreover, we show that VdAve1, and also the newly identified antimicrobial effector VdAMP2, are exploited for microbiome manipulation in the soil environment, where the fungus resides in absence of a host. In conclusion, we demonstrate that a fungal plant pathogen uses effector proteins to modulate microbiome compositions inside and outside the host, and propose that pathogen effector catalogues represent an untapped resource for new antibiotics.
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Affiliation(s)
- Nick C Snelders
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
| | - Hanna Rovenich
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
| | - Gabriella C Petti
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
- Institute of Microbiology, ETH Zürich, Zürich, Switzerland
| | - Mercedes Rocafort
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Grardy C M van den Berg
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
| | | | - Jeroen R Mesters
- Institute of Biochemistry, University of Lübeck, Center for Structural and Cell Biology in Medicine, Lübeck, Germany
| | - Michael F Seidl
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
- Theoretical Biology & Bioinformatics Group, Department of Biology, Utrecht University, Utrecht, the Netherlands
| | - Reindert Nijland
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands
- Marine Animal Ecology Group, Wageningen University and Research, Wageningen, the Netherlands
| | - Bart P H J Thomma
- Laboratory of Phytopathology, Wageningen University and Research, Wageningen, the Netherlands.
- Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Botanical Institute, Cologne, Germany.
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155
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Wood TE, Aksoy E, Hachani A. From Welfare to Warfare: The Arbitration of Host-Microbiota Interplay by the Type VI Secretion System. Front Cell Infect Microbiol 2020; 10:587948. [PMID: 33194832 PMCID: PMC7604300 DOI: 10.3389/fcimb.2020.587948] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 09/22/2020] [Indexed: 12/17/2022] Open
Abstract
The health of mammals depends on a complex interplay with their microbial ecosystems. Compartments exposed to external environments such as the mucosal surfaces of the gastrointestinal tract accommodate the gut microbiota, composed by a wide range of bacteria. The gut microbiome confers benefits to the host, including expansion of metabolic potential and the development of an immune system that can robustly protect from external and internal insults. The cooperation between gut microbiome and host is enabled in part by the formation of partitioned niches that harbor diverse bacterial phyla. Bacterial secretion systems are commonly employed to manipulate the composition of these local environments. Here, we explore the roles of the bacterial type VI secretion system (T6SS), present in ~25% of gram-negative bacteria, including many symbionts, in the establishment and perturbation of bacterial commensalism, and symbiosis in host mucosal sites. This versatile apparatus drives bacterial competition, although in some cases can also interfere directly with host cells and facilitate nutrient acquisition. In addition, some bacterial pathogens cause disease when their T6SS leads to dysbiosis and subverts host immune responses in defined animal models. This review explores our knowledge of the T6SS in the context of the “host-microbiota-pathogen” triumvirate and examines contexts in which the importance of this secretion system may be underappreciated.
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Affiliation(s)
- Thomas E Wood
- Division of Infectious Diseases, Department of Medicine, Massachusetts General Hospital, Boston, MA, United States.,Department of Microbiology, Harvard Medical School, Boston, MA, United States
| | - Ezra Aksoy
- Centre for Biochemical Pharmacology, William Harvey Research Institute, Queen Mary University of London, London, United Kingdom
| | - Abderrahman Hachani
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, VIC, Australia
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156
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Grishin AV, Karyagina AS, Vasina DV, Vasina IV, Gushchin VA, Lunin VG. Resistance to peptidoglycan-degrading enzymes. Crit Rev Microbiol 2020; 46:703-726. [PMID: 32985279 DOI: 10.1080/1040841x.2020.1825333] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The spread of bacterial strains resistant to commonly used antibiotics urges the development of novel antibacterial compounds. Ideally, these novel antimicrobials should be less prone to the development of resistance. Peptidoglycan-degrading enzymes are a promising class of compounds with a fundamentally different mode of action compared to traditionally used antibiotics. The difference in the mechanism of action implies differences both in the mechanisms of resistance and the chances of its emergence. To critically assess the potential of resistance development to peptidoglycan-degrading enzymes, we review the available evidence for the development of resistance to these enzymes in vitro, along with the known mechanisms of resistance to lysozyme, bacteriocins, autolysins, and phage endolysins. We conclude that genetic determinants of resistance to peptidoglycan-degrading enzymes are unlikely to readily emerge de novo. However, resistance to these enzymes would probably spread by the horizontal transfer between intrinsically resistant and susceptible species. Finally, we speculate that the higher cost of the therapeutics based on peptidoglycan degrading enzymes compared to classical antibiotics might result in less misuse, which in turn would lead to lower selective pressure, making these antibacterials less prone to resistance development.
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Affiliation(s)
- Alexander V Grishin
- N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, Russia.,All-Russia Research Institute of Agricultural Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Anna S Karyagina
- N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, Russia.,All-Russia Research Institute of Agricultural Biotechnology, Russian Academy of Sciences, Moscow, Russia.,A.N. Belozersky Institute of Physical and Chemical Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Daria V Vasina
- N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, Russia.,A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Moscow, Russia
| | - Irina V Vasina
- N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, Russia
| | - Vladimir A Gushchin
- N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, Russia.,Faculty of Biology, M.V. Lomonosov Moscow State University, Moscow, Russia
| | - Vladimir G Lunin
- N.F. Gamaleya National Research Center for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, Russia.,All-Russia Research Institute of Agricultural Biotechnology, Russian Academy of Sciences, Moscow, Russia
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157
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Robitaille S, Trus E, Ross BD. Bacterial Defense against the Type VI Secretion System. Trends Microbiol 2020; 29:187-190. [PMID: 32951987 DOI: 10.1016/j.tim.2020.09.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/27/2020] [Accepted: 09/01/2020] [Indexed: 12/26/2022]
Abstract
Bacteria have evolved systems dedicated to interbacterial competition. Here we highlight defenses utilized by Gram-negative cells against type VI secretion system (T6SS)-wielding competitors, including physical barriers, genetically encoded antidotes, and stress responses. Further investigation of specific and general defenses will reveal the interbacterial selective pressures impacting bacterial survival in nature.
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Affiliation(s)
- Sophie Robitaille
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Evan Trus
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA
| | - Benjamin D Ross
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA.
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158
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Bergkessel M. Regulation of protein biosynthetic activity during growth arrest. Curr Opin Microbiol 2020; 57:62-69. [PMID: 32858411 DOI: 10.1016/j.mib.2020.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 07/18/2020] [Accepted: 07/20/2020] [Indexed: 01/10/2023]
Abstract
Heterotrophic bacteria grow and divide rapidly when resources are abundant. Yet resources are finite, and environments fluctuate, so bacteria need strategies to survive when nutrients become scarce. In fact, many bacteria spend most of their time in such conditions of nutrient limitation, and hence they need to optimise gene regulation and protein biosynthesis during growth arrest. An optimal strategy in these conditions must mitigate the challenges and risks of making new proteins, while the cell is severely limited for energy and substrates. Recently, ribosome abundance and activity were measured in these conditions, revealing very low amounts of new protein synthesis, which is nevertheless vital for survival. The underlying mechanisms are only now starting to be explored. Improving our understanding of the regulation of protein production during bacterial growth arrest could have important implications for a wide range of challenges, including the identification of new targets for antibiotic development.
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Affiliation(s)
- Megan Bergkessel
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK.
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159
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Ting SY, Martínez-García E, Huang S, Bertolli SK, Kelly KA, Cutler KJ, Su ED, Zhi H, Tang Q, Radey MC, Raffatellu M, Peterson SB, de Lorenzo V, Mougous JD. Targeted Depletion of Bacteria from Mixed Populations by Programmable Adhesion with Antagonistic Competitor Cells. Cell Host Microbe 2020; 28:313-321.e6. [PMID: 32470328 PMCID: PMC7725374 DOI: 10.1016/j.chom.2020.05.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 04/21/2020] [Accepted: 05/06/2020] [Indexed: 01/15/2023]
Abstract
Selective and targeted removal of individual species or strains of bacteria from complex communities can be desirable over traditional, broadly acting antibacterials in several contexts. However, generalizable strategies that accomplish this with high specificity have been slow to emerge. Here we develop programmed inhibitor cells (PICs) that direct the potent antibacterial activity of the type VI secretion system (T6SS) against specified target cells. The PICs express surface-displayed nanobodies that mediate antigen-specific cell-cell adhesion to effectively overcome the barrier to T6SS activity in fluid conditions. We demonstrate the capacity of PICs to efficiently deplete low-abundance target bacteria without significant collateral damage to complex microbial communities. The only known requirements for PIC targeting are a Gram-negative cell envelope and a unique cell surface antigen; therefore, this approach should be generalizable to a wide array of bacteria and find application in medical, research, and environmental settings.
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Affiliation(s)
- See-Yeun Ting
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | | | - Shuo Huang
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Savannah K Bertolli
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Katherine A Kelly
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Kevin J Cutler
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | - Elizabeth D Su
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Hui Zhi
- Division of Host-Microbe Systems & Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA
| | - Qing Tang
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Matthew C Radey
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Manuela Raffatellu
- Division of Host-Microbe Systems & Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; Center for Microbiome Innovation, University of California San Diego, La Jolla, CA 92093, USA; Chiba University-UC San Diego Center for Mucosal Immunology, Allergy, and Vaccines (CU-UCSD cMAV), La Jolla, CA 92093, USA
| | - S Brook Peterson
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Víctor de Lorenzo
- System Biology Program, National Center of Biotechnology CSIC, 28049 Madrid, Spain
| | - Joseph D Mougous
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Biochemistry, University of Washington School of Medicine, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
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160
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Draft Genome Sequence of Stenotrophomonas maltophilia MDMC339, Isolated from Soil of Merzouga Desert in Morocco. Microbiol Resour Announc 2020; 9:9/32/e00634-20. [PMID: 32763932 PMCID: PMC7409849 DOI: 10.1128/mra.00634-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Here, we report the draft genome sequence of Stenotrophomonas maltophilia MDMC339, a strain able to survive in the difficult conditions imposed by the Merzouga desert. The analyzed genome contains 4,788,525 bp with 4,262 genes coding for proteins, including several genes related to stress. Here, we report the draft genome sequence of Stenotrophomonas maltophilia MDMC339, a strain able to survive in the difficult conditions imposed by the Merzouga desert. The analyzed genome contains 4,788,525 bp with 4,262 genes coding for proteins, including several genes related to stress.
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161
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Hernandez RE, Gallegos‐Monterrosa R, Coulthurst SJ. Type
VI
secretion system effector proteins: Effective weapons for bacterial competitiveness. Cell Microbiol 2020; 22:e13241. [DOI: 10.1111/cmi.13241] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 06/08/2020] [Accepted: 06/15/2020] [Indexed: 12/31/2022]
Affiliation(s)
- Ruth E. Hernandez
- Division of Molecular Microbiology, School of Life SciencesUniversity of Dundee Dundee UK
| | | | - Sarah J. Coulthurst
- Division of Molecular Microbiology, School of Life SciencesUniversity of Dundee Dundee UK
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162
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Mok BY, de Moraes MH, Zeng J, Bosch DE, Kotrys AV, Raguram A, Hsu F, Radey MC, Peterson SB, Mootha VK, Mougous JD, Liu DR. A bacterial cytidine deaminase toxin enables CRISPR-free mitochondrial base editing. Nature 2020; 583:631-637. [PMID: 32641830 PMCID: PMC7381381 DOI: 10.1038/s41586-020-2477-4] [Citation(s) in RCA: 378] [Impact Index Per Article: 94.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Accepted: 05/26/2020] [Indexed: 12/21/2022]
Abstract
Bacterial toxins represent a vast reservoir of biochemical diversity that can be repurposed for biomedical applications. Such proteins include a group of predicted interbacterial toxins of the deaminase superfamily, members of which have found application in gene-editing techniques1,2. Because previously described cytidine deaminases operate on single-stranded nucleic acids3, their use in base editing requires the unwinding of double-stranded DNA (dsDNA)-for example by a CRISPR-Cas9 system. Base editing within mitochondrial DNA (mtDNA), however, has thus far been hindered by challenges associated with the delivery of guide RNA into the mitochondria4. As a consequence, manipulation of mtDNA to date has been limited to the targeted destruction of the mitochondrial genome by designer nucleases9,10.Here we describe an interbacterial toxin, which we name DddA, that catalyses the deamination of cytidines within dsDNA. We engineered split-DddA halves that are non-toxic and inactive until brought together on target DNA by adjacently bound programmable DNA-binding proteins. Fusions of the split-DddA halves, transcription activator-like effector array proteins, and a uracil glycosylase inhibitor resulted in RNA-free DddA-derived cytosine base editors (DdCBEs) that catalyse C•G-to-T•A conversions in human mtDNA with high target specificity and product purity. We used DdCBEs to model a disease-associated mtDNA mutation in human cells, resulting in changes in respiration rates and oxidative phosphorylation. CRISPR-free DdCBEs enable the precise manipulation of mtDNA, rather than the elimination of mtDNA copies that results from its cleavage by targeted nucleases, with broad implications for the study and potential treatment of mitochondrial disorders.
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Affiliation(s)
- Beverly Y Mok
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - Marcos H de Moraes
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
| | - Jun Zeng
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
| | - Dustin E Bosch
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
- Department of Pathology, University of Washington School of Medicine, Seattle, WA, USA
| | - Anna V Kotrys
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland
| | - Aditya Raguram
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - FoSheng Hsu
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
| | - Matthew C Radey
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
| | - S Brook Peterson
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
| | - Vamsi K Mootha
- Howard Hughes Medical Institute and Department of Molecular Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
| | - Joseph D Mougous
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA.
- Department of Biochemistry, University of Washington School of Medicine, Seattle, WA, USA.
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA.
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA.
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA.
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163
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Le NH, Peters K, Espaillat A, Sheldon JR, Gray J, Di Venanzio G, Lopez J, Djahanschiri B, Mueller EA, Hennon SW, Levin PA, Ebersberger I, Skaar EP, Cava F, Vollmer W, Feldman MF. Peptidoglycan editing provides immunity to Acinetobacter baumannii during bacterial warfare. SCIENCE ADVANCES 2020; 6:eabb5614. [PMID: 32832672 PMCID: PMC7439305 DOI: 10.1126/sciadv.abb5614] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 06/09/2020] [Indexed: 05/02/2023]
Abstract
Peptidoglycan (PG) is essential in most bacteria. Thus, it is often targeted by various assaults, including interbacterial attacks via the type VI secretion system (T6SS). Here, we report that the Gram-negative bacterium Acinetobacter baumannii strain ATCC 17978 produces, secretes, and incorporates the noncanonical d-amino acid d-lysine into its PG during stationary phase. We show that PG editing increases the competitiveness of A. baumannii during bacterial warfare by providing immunity against peptidoglycan-targeting T6SS effectors from various bacterial competitors. In contrast, we found that d-Lys production is detrimental to pathogenesis due, at least in part, to the activity of the human enzyme d-amino acid oxidase (DAO), which degrades d-Lys producing H2O2 toxic to bacteria. Phylogenetic analyses indicate that the last common ancestor of A. baumannii had the ability to produce d-Lys. However, this trait was independently lost multiple times, likely reflecting the evolution of A. baumannii as a human pathogen.
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Affiliation(s)
- Nguyen-Hung Le
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Katharina Peters
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, NE2 4AX Newcastle upon Tyne, UK
| | - Akbar Espaillat
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, 90187 Umeå, Sweden
| | - Jessica R. Sheldon
- Department of Pathology, Microbiology, and Immunology and Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Joe Gray
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Gisela Di Venanzio
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Juvenal Lopez
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Bardya Djahanschiri
- Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt am Main 60438, Germany
| | - Elizabeth A. Mueller
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63105, USA
| | - Seth W. Hennon
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Petra Anne Levin
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63105, USA
| | - Ingo Ebersberger
- Applied Bioinformatics Group, Institute of Cell Biology and Neuroscience, Goethe University Frankfurt, Frankfurt am Main 60438, Germany
- LOEWE Center for Translational Biodiversity Genomics (TBG), Senckenberganlage 25, D-60325 Frankfurt am Main, Germany
- Senckenberg Biodiversity and Climate Research Center (S-BIKF), Senckenberganlage 25, D-60325 Frankfurt am Main, Germany
| | - Eric P. Skaar
- Department of Pathology, Microbiology, and Immunology and Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Felipe Cava
- Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University, 90187 Umeå, Sweden
| | - Waldemar Vollmer
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, NE2 4AX Newcastle upon Tyne, UK
| | - Mario F. Feldman
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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164
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Chien CF, Liu CY, Lu YY, Sung YH, Chen KY, Lin NC. HSI-II Gene Cluster of Pseudomonas syringae pv. tomato DC3000 Encodes a Functional Type VI Secretion System Required for Interbacterial Competition. Front Microbiol 2020; 11:1118. [PMID: 32582082 PMCID: PMC7283901 DOI: 10.3389/fmicb.2020.01118] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 05/05/2020] [Indexed: 11/13/2022] Open
Abstract
The type VI secretion system (T6SS) is a widespread bacterial nanoweapon used for delivery of toxic proteins into cell targets and contributes to virulence, anti-inflammatory processes, and interbacterial competition. In the model phytopathogenic bacterium Pseudomonas syringae pv. tomato (Pst) DC3000, two T6SS gene clusters, HSI-I and HSI-II, were identified, but their functions remain unclear. We previously reported that hcp2, located in HSI-II, is involved in competition with enterobacteria and yeast. Here, we demonstrated that interbacterial competition of Pst DC3000 against several Gram-negative plant-associated bacteria requires mainly HSI-II activity. By means of a systematic approach using in-frame deletion mutants for each gene in the HSI-II cluster, we identified genes indispensable for Hcp2 expression, Hcp2 secretion and interbacterial competition ability. Deletion of PSPTO_5413 only affected growth in interbacterial competition assays but not Hcp2 secretion, which suggests that PSPTO_5413 might be a putative effector. Moreover, PSPTO_5424, encoding a putative σ54-dependent transcriptional regulator, positively regulated the expression of all three operons in HSI-II. Our discovery that the HSI-II gene cluster gives Pst DC3000 the ability to compete with other plant-associated bacteria could help in understanding a possible mechanism of how phytopathogenic bacteria maintain their ecological niches.
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Affiliation(s)
- Ching-Fang Chien
- Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
| | - Cheng-Ying Liu
- Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
| | - Yew-Yee Lu
- Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
| | - You-Hsing Sung
- Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
| | - Kuo-Yau Chen
- Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
| | - Nai-Chun Lin
- Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan
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165
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A Family of T6SS Antibacterial Effectors Related to l,d-Transpeptidases Targets the Peptidoglycan. Cell Rep 2020; 31:107813. [DOI: 10.1016/j.celrep.2020.107813] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/20/2020] [Accepted: 06/03/2020] [Indexed: 12/17/2022] Open
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166
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Bleves S, Galán JE, Llosa M. Bacterial injection machines: Evolutionary diverse but functionally convergent. Cell Microbiol 2020; 22:e13157. [PMID: 31891220 PMCID: PMC7138736 DOI: 10.1111/cmi.13157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 12/19/2019] [Indexed: 12/23/2022]
Abstract
Many human pathogens use Type III, Type IV, and Type VI secretion systems to deliver effectors into their target cells. The contribution of these secretion systems to microbial virulence was the main focus of a workshop organised by the International University of Andalusia in Spain. The meeting addressed structure-function, substrate recruitment, and translocation processes, which differ widely on the different secretion machineries, as well as the nature of the translocated effectors and their roles in subverting the host cell. An excellent panel of worldwide speakers presented the state of the art of the field, highlighting the involvement of bacterial secretion in human disease and discussing mechanistic aspects of bacterial pathogenicity, which can provide the bases for the development of novel antivirulence strategies.
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Affiliation(s)
- Sophie Bleves
- LISM (Laboratoire d’Ingénierie des Systèmes Macromoléculaires-UMR7255), IMM (Institut de Microbiologie de la Méditerranée), Aix-Marseille Univ and CNRS, Marseille, France
| | - Jorge E. Galán
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, USA
| | - Matxalen Llosa
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria-CSIC-SODERCAN, Santander, Spain
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167
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Fur-Dam Regulatory Interplay at an Internal Promoter of the Enteroaggregative Escherichia coli Type VI Secretion sci1 Gene Cluster. J Bacteriol 2020; 202:JB.00075-20. [PMID: 32152218 DOI: 10.1128/jb.00075-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 02/28/2020] [Indexed: 12/17/2022] Open
Abstract
The type VI secretion system (T6SS) is a weapon for delivering effectors into target cells that is widespread in Gram-negative bacteria. The T6SS is a highly versatile machine, as it can target both eukaryotic and prokaryotic cells, and it has been proposed that T6SSs are adapted to the specific needs of each bacterium. The expression of T6SS gene clusters and the activation of the secretion apparatus are therefore tightly controlled. In enteroaggregative Escherichia coli (EAEC), the sci1 T6SS gene cluster is subject to a complex regulation involving both the ferric uptake regulator (Fur) and DNA adenine methylase (Dam)-dependent DNA methylation. In this study, an additional, internal, promoter was identified within the sci1 gene cluster using +1 transcriptional mapping. Further analyses demonstrated that this internal promoter is controlled by a mechanism strictly identical to that of the main promoter. The Fur binding box overlaps the -10 transcriptional element and a Dam methylation site, GATC-32. Hence, the expression of the distal sci1 genes is repressed and the GATC-32 site is protected from methylation in iron-rich conditions. The Fur-dependent protection of GATC-32 was confirmed by an in vitro methylation assay. In addition, the methylation of GATC-32 negatively impacted Fur binding. The expression of the sci1 internal promoter is therefore controlled by iron availability through Fur regulation, whereas Dam-dependent methylation maintains a stable ON expression in iron-limited conditions.IMPORTANCE Bacteria use weapons to deliver effectors into target cells. One of these weapons, the type VI secretion system (T6SS), assembles a contractile tail acting as a spring to propel a toxin-loaded needle. Its expression and activation therefore need to be tightly regulated. Here, we identified an internal promoter within the sci1 T6SS gene cluster in enteroaggregative E. coli We show that this internal promoter is controlled by Fur and Dam-dependent methylation. We further demonstrate that Fur and Dam compete at the -10 transcriptional element to finely tune the expression of T6SS genes. We propose that this elegant regulatory mechanism allows the optimum production of the T6SS in conditions where enteroaggregative E. coli encounters competing species.
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168
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Wang T, Hu Z, Du X, Shi Y, Dang J, Lee M, Hesek D, Mobashery S, Wu M, Liang H. A type VI secretion system delivers a cell wall amidase to target bacterial competitors. Mol Microbiol 2020; 114:308-321. [PMID: 32279364 DOI: 10.1111/mmi.14513] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 04/02/2020] [Accepted: 04/02/2020] [Indexed: 01/22/2023]
Abstract
The human pathogen Pseudomonas aeruginosa harbors three paralogous zinc proteases annotated as AmpD, AmpDh2, and AmpDh3, which turn over the cell wall and cell wall-derived muropeptides. AmpD is cytoplasmic and plays a role in the recycling of cell wall muropeptides, with a link to antibiotic resistance. AmpDh2 is a periplasmic soluble enzyme with the former anchored to the inner leaflet of the outer membrane. We document, herein, that the type VI secretion system locus II (H2-T6SS) of P. aeruginosa delivers AmpDh3 (but not AmpD or AmpDh2) to the periplasm of a prey bacterium upon contact. AmpDh3 hydrolyzes the cell wall peptidoglycan of the prey bacterium, which leads to its killing, thereby providing a growth advantage for P. aeruginosa in bacterial competition. We also document that the periplasmic protein PA0808, heretofore of unknown function, affords self-protection from lysis by AmpDh3. Cognates of the AmpDh3-PA0808 pair are widely distributed across Gram-negative bacteria. Taken together, these findings underscore the importance of their function as an evolutionary advantage and that of the H2-T6SS as the means for the manifestation of the effect.
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Affiliation(s)
- Tietao Wang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Zhaoyu Hu
- Systems Biology Theme, Department of Biomedical Engineering, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Xiao Du
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Yue Shi
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Jing Dang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Mijoon Lee
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
| | - Dusan Hesek
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, USA
| | - Min Wu
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, Grand Forks, ND, USA
| | - Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
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169
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Abstract
Symbiotic bacteria use diverse strategies to compete for host colonization sites. However, little is known about the environmental cues that modulate interbacterial competition as they transition between free-living and host-associated lifestyles. We used the mutualistic relationship between Eupyrmna scolopes squid and Vibrio fischeri bacteria to investigate how intraspecific competition is regulated as symbionts move from the seawater to a host-like environment. We recently reported that V. fischeri uses a type VI secretion system (T6SS) for intraspecific competition during host colonization. Here, we investigated how environmental viscosity impacts T6SS-mediated competition by using a liquid hydrogel medium that mimics the viscous host environment. Our data demonstrate that although the T6SS is functionally inactive when cells are grown under low-viscosity liquid conditions similar to those found in seawater, exposure to a host-like high-viscosity hydrogel enhances T6SS expression and sheath formation, activates T6SS-mediated killing in as little as 30 min, and promotes the coaggregation of competing genotypes. Finally, the use of mass spectrometry-based proteomics revealed insights into how cells may prepare for T6SS competition during this habitat transition. These findings, which establish the use of a new hydrogel culture condition for studying T6SS interactions, indicate that V. fischeri rapidly responds to the physical environment to activate the competitive mechanisms used during host colonization.IMPORTANCE Bacteria often engage in interference competition to gain access to an ecological niche, such as a host. However, little is known about how the physical environment experienced by free-living or host-associated bacteria influences such competition. We used the bioluminescent squid symbiont Vibrio fischeri to study how environmental viscosity impacts bacterial competition. Our results suggest that upon transition from a planktonic environment to a host-like environment, V. fischeri cells activate their type VI secretion system, a contact-dependent interbacterial nanoweapon, to eliminate natural competitors. This work shows that competitor cells form aggregates under host-like conditions, thereby facilitating the contact required for killing, and reveals how V. fischeri regulates a key competitive mechanism in response to the physical environment.
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170
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Wasai-Hara S, Hara S, Morikawa T, Sugawara M, Takami H, Yoneda J, Tokunaga T, Minamisawa K. Diversity of Bradyrhizobium in Non-Leguminous Sorghum Plants: B. ottawaense Isolates Unique in Genes for N 2O Reductase and Lack of the Type VI Secretion System. Microbes Environ 2020; 35. [PMID: 31932539 PMCID: PMC7104290 DOI: 10.1264/jsme2.me19102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Diverse members of Bradyrhizobium diazoefficiens, B. japonicum, and B. ottawaense were isolated from the roots of field-grown sorghum plants in Fukushima, and classified into “Rhizobia” with nodulated soybeans, “Free-living diazotrophs”, and “Non-diazotrophs” by nitrogen fixation and nodulation assays. Genome analyses revealed that B. ottawaense members possessed genes for N2O reduction, but lacked those for the Type VI secretion system (T6SS). T6SS is a new bacterial weapon against microbial competitors. Since T6SS-possessing B. diazoefficiens and B. japonicum have mainly been isolated from soybean nodules in Japan, T6SS-lacking B. ottawaense members may be a cryptic lineage of soybean bradyrhizobia in Japan.
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Affiliation(s)
| | | | | | | | - Hideto Takami
- Yokohama Institute, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
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171
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Hardy BL, Bansal G, Hewlett KH, Arora A, Schaffer SD, Kamau E, Bennett JW, Merrell DS. Antimicrobial Activity of Clinically Isolated Bacterial Species Against Staphylococcus aureus. Front Microbiol 2020; 10:2977. [PMID: 32010080 PMCID: PMC6975196 DOI: 10.3389/fmicb.2019.02977] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Accepted: 12/10/2019] [Indexed: 11/24/2022] Open
Abstract
Bacteria often exist in polymicrobial communities where they compete for limited resources. Intrinsic to this competition is the ability of some species to inhibit or kill their competitors. This phenomenon is pervasive throughout the human body where commensal bacteria block the colonization of incoming microorganisms. In this regard, molecular epidemiological and microbiota-based studies suggest that species-specific interactions play a critical role in the prevention of nasal colonization of the opportunistic pathogen Staphylococcus aureus. Despite this, S. aureus exists as part of the microbiota of ∼25% of the population, suggesting that the interplay between S. aureus and commensals can be complex. Microbiota studies indicate that several bacterial genera are negatively correlated with S. aureus colonization. While these studies paint a broad overview of bacterial presence, they often fail to identify individual species-specific interactions; a greater insight in this area could aid the development of novel antimicrobials. As a proof of concept study designed to identify individual bacterial species that possess anti-S. aureus activity, we screened a small collection of clinical isolates from the Walter Reed National Military Medical Center for the ability to inhibit multiple S. aureus strains. We found that the majority of the isolates (82%) inhibited at least one S. aureus strain; 23% inhibited all S. aureus strains tested. In total, seven isolates mediated inhibitory activity that was independent of physical contact with S. aureus, and seven isolates mediated bactericidal activity. 16S rRNA based-sequencing revealed that the inhibitory isolates belonged to the Acinetobacter, Agromyces, Corynebacterium, Microbacteria, Mycobacterium, and Staphylococcus genera. Unexpectedly, these included seven distinct Acinetobacter baumannii isolates, all of which showed heterogeneous degrees of anti-S. aureus activity. Defined mechanistic studies on specific isolates revealed that the inhibitory activity was retained in conditioned cell free medium (CCFM) derived from the isolates. Furthermore, CCFM obtained from S. saprophyticus significantly decreased mortality of S. aureus-infected Galleria mellonella caterpillars. While future studies will seek to define the molecular mechanisms of the inhibitory activities, our current findings support the study of polymicrobial interactions as a strategy to understand bacterial competition and to identify novel therapeutics against S. aureus and other pathogens.
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Affiliation(s)
- Britney L Hardy
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Garima Bansal
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Katharine H Hewlett
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Arshia Arora
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Scott D Schaffer
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Edwin Kamau
- Department of Clinical Microbiology, Walter Reed National Military Medical Center, Bethesda, MD, United States.,U.S. Military HIV Research Program, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Jason W Bennett
- Multidrug-Resistant Organism Repository and Surveillance Network, Walter Reed Army Institute of Research, Silver Spring, MD, United States.,Department of Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - D Scott Merrell
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States.,Department of Medicine, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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172
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Allsopp LP, Bernal P, Nolan LM, Filloux A. Causalities of war: The connection between type VI secretion system and microbiota. Cell Microbiol 2020; 22:e13153. [PMID: 31872954 PMCID: PMC7540082 DOI: 10.1111/cmi.13153] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 11/23/2019] [Accepted: 12/19/2019] [Indexed: 12/14/2022]
Abstract
Microbiota niches have space and/or nutrient restrictions, which has led to the coevolution of cooperation, specialisation, and competition within the population. Different animal and environmental niches contain defined resident microbiota that tend to be stable over time and offer protection against undesired intruders. Yet fluxes can occur, which alter the composition of a bacterial population. In humans, the microbiota are now considered a key contributor to maintenance of health and homeostasis, and its alteration leads to dysbiosis. The bacterial type VI secretion system (T6SS) transports proteins into the environment, directly into host cells or can function as an antibacterial weapon by killing surrounding competitors. Upon contact with neighbouring cells, the T6SS fires, delivering a payload of effector proteins. In the absence of an immunity protein, this results in growth inhibition or death of prey leading to a competitive advantage for the attacker. It is becoming apparent that the T6SS has a role in modulating and shaping the microbiota at multiple levels, which is the focus of this review. Discussed here is the T6SS, its role in competition, key examples of its effect upon the microbiota, and future avenues of research.
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Affiliation(s)
- Luke P Allsopp
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Patricia Bernal
- Department of Biology, Faculty of Sciences, Universidad Autónoma de Madrid, Madrid, Spain
| | - Laura M Nolan
- National Heart and Lung Institute, Imperial College London, London, UK
| | - Alain Filloux
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, UK
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173
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Toxin discovery reveals fresh ammunition for bacterial warfare. Nature 2020; 575:599-600. [PMID: 31768037 DOI: 10.1038/d41586-019-03217-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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174
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Gestal MC, Johnson HM, Harvill ET. Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections. Front Immunol 2019; 10:2869. [PMID: 31921136 PMCID: PMC6923730 DOI: 10.3389/fimmu.2019.02869] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 11/22/2019] [Indexed: 12/13/2022] Open
Abstract
Well-adapted pathogens have evolved to survive the many challenges of a robust immune response. Defending against all host antimicrobials simultaneously would be exceedingly difficult, if not impossible, so many co-evolved organisms utilize immunomodulatory tools to subvert, distract, and/or evade the host immune response. Bordetella spp. present many examples of the diversity of immunomodulators and an exceptional experimental system in which to study them. Recent advances in this experimental system suggest strategies for interventions that tweak immunity to disrupt bacterial immunomodulation, engaging more effective host immunity to better prevent and treat infections. Here we review advances in the understanding of respiratory pathogens, with special focus on Bordetella spp., and prospects for the use of immune-stimulatory interventions in the prevention and treatment of infection.
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Affiliation(s)
- Monica C Gestal
- Department of Infectious Diseases, College of Veterinary Sciences, University of Georgia, Athens, GA, United States
| | - Hannah M Johnson
- Department of Infectious Diseases, College of Veterinary Sciences, University of Georgia, Athens, GA, United States
| | - Eric T Harvill
- Department of Infectious Diseases, College of Veterinary Sciences, University of Georgia, Athens, GA, United States
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175
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Han Y, Wang T, Chen G, Pu Q, Liu Q, Zhang Y, Xu L, Wu M, Liang H. A Pseudomonas aeruginosa type VI secretion system regulated by CueR facilitates copper acquisition. PLoS Pathog 2019; 15:e1008198. [PMID: 31790504 PMCID: PMC6907878 DOI: 10.1371/journal.ppat.1008198] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Revised: 12/12/2019] [Accepted: 11/07/2019] [Indexed: 12/13/2022] Open
Abstract
The type VI secretion system (T6SS) is widely distributed in Gram-negative bacteria, whose function is known to translocate substrates to eukaryotic and prokaryotic target cells to cause host damage or as a weapon for interbacterial competition. Pseudomonas aeruginosa encodes three distinct T6SS clusters (H1-, H2-, and H3-T6SS). The H1-T6SS-dependent substrates have been identified and well characterized; however, only limited information is available for the H2- and H3-T6SSs since relatively fewer substrates for them have yet been established. Here, we obtained P. aeruginosa H2-T6SS-dependent secretomes and further characterized the H2-T6SS-dependent copper (Cu2+)-binding effector azurin (Azu). Our data showed that both azu and H2-T6SS were repressed by CueR and were induced by low concentrations of Cu2+. We also identified the Azu-interacting partner OprC, a Cu2+-specific TonB-dependent outer membrane transporter. Similar to H2-T6SS genes and azu, expression of oprC was directly regulated by CueR and was induced by low Cu2+. In addition, the Azu-OprC-mediated Cu2+ transport system is critical for P. aeruginosa cells in bacterial competition and virulence. Our findings provide insights for understanding the diverse functions of T6SSs and the role of metal ions for P. aeruginosa in bacteria-bacteria competition. The type VI secretion system (T6SS) is a specific macromolecular protein export apparatus, and widely distributed in Gram-negative bacteria. T6SS plays an important role in anti-bacterial competition or delivers effector proteins to both eukaryotic and prokaryotic cells. In the present study, we performed secretomes analysis and identified 21 substrates of P. aeruginosa H2-T6SS-dependent. Specifically, we report a Cu2+-scavenging pathway consisting of a copper transporter, OprC, and a type VI secretion system (H2-T6SS)-secreted Cu2+-binding protein, Azu. Both of them are under control of the transcriptional regulator CueR. Indeed, the Azu-OprC-mediated Cu2+ transport system is critical for P. aeruginosa cells in bacterial competition and virulence. These findings exemplify how P. aeruginosa deploys this metal system to adapt to the complex environment during evolution.
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Affiliation(s)
- Yuying Han
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Tietao Wang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Gukui Chen
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Qinqin Pu
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, Grand Forks, North Dakota, United States of America
| | - Qiong Liu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, GuangDong, China
| | - Yani Zhang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
| | - Linghui Xu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, GuangDong, China
| | - Min Wu
- Department of Basic Science, School of Medicine and Health Science, University of North Dakota, Grand Forks, North Dakota, United States of America
| | - Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, ShaanXi, China
- * E-mail:
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176
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Mariano G, Trunk K, Williams DJ, Monlezun L, Strahl H, Pitt SJ, Coulthurst SJ. A family of Type VI secretion system effector proteins that form ion-selective pores. Nat Commun 2019; 10:5484. [PMID: 31792213 PMCID: PMC6889166 DOI: 10.1038/s41467-019-13439-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 11/05/2019] [Indexed: 12/25/2022] Open
Abstract
Type VI secretion systems (T6SSs) are nanomachines widely used by bacteria to deliver toxic effector proteins directly into neighbouring cells. However, the modes of action of many effectors remain unknown. Here we report that Ssp6, an anti-bacterial effector delivered by a T6SS of the opportunistic pathogen Serratia marcescens, is a toxin that forms ion-selective pores. Ssp6 inhibits bacterial growth by causing depolarisation of the inner membrane in intoxicated cells, together with increased outer membrane permeability. Reconstruction of Ssp6 activity in vitro demonstrates that it forms cation-selective pores. A survey of bacterial genomes reveals that genes encoding Ssp6-like effectors are widespread in Enterobacteriaceae and often linked with T6SS genes. We conclude that Ssp6 and similar proteins represent a new family of T6SS-delivered anti-bacterial effectors.
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Affiliation(s)
- Giuseppina Mariano
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Katharina Trunk
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - David J Williams
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Laura Monlezun
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK
| | - Henrik Strahl
- Centre for Bacterial Cell Biology, Newcastle University, Richardson Road, Newcastle-upon-Tyne, NE2 4AX, UK
| | - Samantha J Pitt
- School of Medicine, University of St Andrews, North Haugh, St Andrews, KY16 9TF, UK
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dow St, Dundee, DD1 5EH, UK.
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177
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Santin YG, Doan T, Journet L, Cascales E. Cell Width Dictates Type VI Secretion Tail Length. Curr Biol 2019; 29:3707-3713.e3. [DOI: 10.1016/j.cub.2019.08.058] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/25/2019] [Accepted: 08/21/2019] [Indexed: 01/22/2023]
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178
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Zhu PC, Li YM, Yang X, Zou HF, Zhu XL, Niu XN, Xu LH, Jiang W, Huang S, Tang JL, He YQ. Type VI secretion system is not required for virulence on rice but for inter-bacterial competition in Xanthomonas oryzae pv. oryzicola. Res Microbiol 2019; 171:64-73. [PMID: 31676435 DOI: 10.1016/j.resmic.2019.10.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Revised: 10/17/2019] [Accepted: 10/17/2019] [Indexed: 11/28/2022]
Abstract
The type VI secretion system (T6SS), a multifunctional protein secretion device, plays very important roles in bacterial killing and/or virulence to eukaryotic cells. Although T6SS genes have been found in many Xanthomonas species, the biological function of T6SSs has not been elucidated in most xanthomonads. In this study, we identified two phylogenetically distinct T6SS clusters, T6SS1 and T6SS2, in a newly sequenced Chinese strain GX01 of Xanthomonas oryzea pv. oryzicola (Xoc) which causes bacterial leaf streak (BLS) of rice (Oryza sativa L.). Mutational assays demonstrated that T6SS1 and T6SS2 are not required for the virulence of Xoc GX01 on rice. Nevertheless, we found that T6SS2, but not T6SS1, played an important role in bacterial killing. Transcription and secretion analysis revealed that hcp2 gene is actively expressed and that Hcp2 protein is secreted via T6SS. Moreover, several candidate T6SS effectors were predicted by bioinformatics analysis that might play a role in the antibacterial activity of Xoc. This is the first report to investigate the type VI secretion system in Xanthomonas oryzae. We speculate that Xoc T6SS2 might play an important role in inter-bacterial competition, allowing this plant pathogen to gain niche advantage by killing other bacteria.
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Affiliation(s)
- Ping-Chuan Zhu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Yi-Ming Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Xia Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Hai-Fan Zou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Xiao-Lin Zhu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Xiang-Na Niu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Ling-Hui Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Wei Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Sheng Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China
| | - Ji-Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China.
| | - Yong-Qiang He
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China; National Demonstration Center for Experimental Plant Science Education, College of Agriculture, Guangxi University, 100 Daxue Road, Nanning, Guangxi, 530004, China.
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179
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Crystal structure of PppA from Pseudomonas aeruginosa, a key regulatory component of type VI secretion systems. Biochem Biophys Res Commun 2019; 516:196-201. [PMID: 31208722 DOI: 10.1016/j.bbrc.2019.06.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Accepted: 06/03/2019] [Indexed: 11/20/2022]
Abstract
The Type VI secretion system (T6SS) is a membrane protein complex related to inter-bacterial competitions and host-pathogen interactions in Pseudomonas aeruginosa. The T6SS is regulated by a great variety of regulatory mechanisms at multiple levels, including post-translational modification with threonine phosphorylation mediated by Ser/Thr protein kinase PpkA and phosphatase PppA. The T6SS is activated by PpkA via Thr phosphorylation of Fha, and PppA can antagonize PpkA. PppA is a PP2C-family protein phosphatase and plays a key role in the disassembly and reassembly of T6SS organelles. Herein, we report the first crystal structure of PppA from Pseudomonas aeruginosa, which was determined at a resolution of 2.10 Å. The overall structure consists of a bacteria PPM structural core and a flexible flap subdomain. PppA harbors a catalytic pocket containing two manganese ions which correspond to the canonical dinuclear metal center of Ser/Thr protein phosphatases including the bacterial PPM phosphatases and human PP2C. The flexibility and the diversity of the sequence of flap subdomain across the homologues might provide clues for substrates specific recognition of phosphatases.
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180
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Lennings J, Makhlouf M, Olejnik P, Mayer C, Brötz-Oesterhelt H, Schwarz S. Environmental and cellular factors affecting the localization of T6SS proteins in Burkholderia thailandensis. Int J Med Microbiol 2019; 309:151335. [PMID: 31378704 DOI: 10.1016/j.ijmm.2019.151335] [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: 06/15/2019] [Revised: 07/15/2019] [Accepted: 07/17/2019] [Indexed: 01/22/2023] Open
Abstract
The type VI secretion system (T6SS) injects effector proteins into neighboring bacteria and host cells. Effector translocation is driven by contraction of a tubular sheath in the cytoplasm that expels an inner needle across the cell envelope. The AAA + ATPase ClpV disassembles and recycles the contracted sheath. While ClpV-1-GFP of the Burkholderia T6SS-1, which targets prokaryotic cells, assembles into randomly localized foci, ClpV-5-GFP of the virulence-associated T6SS-5 displays a polar distribution. The mechanisms underlying the localization of T6SSs to a particular site in the bacterial cell are currently unknown. We recently showed that ClpV-5-GFP retains its polar localization in the absence of all T6SS-5 components during infection of host cells. Herein, we set out to identify factors involved in the distribution of ClpV-5 and ClpV-1 in Burkholderia thailandensis. We show that focal assembly and polar localization of ClpV-5-GFP is not dependent on the intracellular host cell environment, known to contain the signal to induce T6SS-5 gene expression. In contrast to ClpV-5-GFP, localization of ClpV-1-GFP was dependent on the cognate T6SS. Foci formation of both ClpV5-GFP and ClpV-1-GFP was decreased by D cycloserine-mediated inhibition of peptidoglycan synthesis while treatment of B. thailandensis with A22 blocking the cytoskeletal protein MreB did not affect assembly of ClpV-5 and ClpV-1 into single discrete foci. Furthermore, we found that surface contact promotes but is not essential for localization of ClpV-5-GFP to the pole whereas expression of clpV-1-gfp appears to be induced by surface contact. In summary, the study provides novel insights into the localization of ClpV ATPases of T6SSs targeting prokaryotic and eukaryotic cells.
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Affiliation(s)
- Jan Lennings
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Munira Makhlouf
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Przemyslaw Olejnik
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany
| | - Christian Mayer
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Microbial Bioactive Compounds, University of Tübingen, Tübingen, Germany
| | - Heike Brötz-Oesterhelt
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Microbial Bioactive Compounds, University of Tübingen, Tübingen, Germany
| | - Sandra Schwarz
- Interfaculty Institute of Microbiology and Infection Medicine, Department of Medical Microbiology and Hygiene, University of Tübingen, Tübingen, Germany.
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181
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Cherrak Y, Flaugnatti N, Durand E, Journet L, Cascales E. Structure and Activity of the Type VI Secretion System. Microbiol Spectr 2019; 7:10.1128/microbiolspec.psib-0031-2019. [PMID: 31298206 PMCID: PMC10957189 DOI: 10.1128/microbiolspec.psib-0031-2019] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Indexed: 12/16/2022] Open
Abstract
The type VI secretion system (T6SS) is a multiprotein machine that uses a spring-like mechanism to inject effectors into target cells. The injection apparatus is composed of a baseplate on which is built a contractile tail tube/sheath complex. The inner tube, topped by the spike complex, is propelled outside of the cell by the contraction of the sheath. The injection system is anchored to the cell envelope and oriented towards the cell exterior by a trans-envelope complex. Effectors delivered by the T6SS are loaded within the inner tube or on the spike complex and can target prokaryotic and/or eukaryotic cells. Here we summarize the structure, assembly, and mechanism of action of the T6SS. We also review the function of effectors and their mode of recruitment and delivery.
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Affiliation(s)
- Yassine Cherrak
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
- Y.C. and N.F. contributed equally to this review
| | - Nicolas Flaugnatti
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
- Y.C. and N.F. contributed equally to this review
- Present address: Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Eric Durand
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
| | - Laure Journet
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
| | - Eric Cascales
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires (LISM), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS, UMR 7255, 13402 Marseille Cedex 20, France
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182
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Chen C, Yang X, Shen X. Confirmed and Potential Roles of Bacterial T6SSs in the Intestinal Ecosystem. Front Microbiol 2019; 10:1484. [PMID: 31316495 PMCID: PMC6611333 DOI: 10.3389/fmicb.2019.01484] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 06/14/2019] [Indexed: 12/25/2022] Open
Abstract
The contact-dependent type VI secretion system (T6SS) in diverse microbes plays crucial roles in both inter-bacterial and bacteria-host interactions. As numerous microorganisms inhabit the intestinal ecosystem at a high density, it is necessary to consider the functions of T6SS in intestinal bacteria. In this mini-review, we discuss T6SS-dependent functions in intestinal microbes, including commensal microbes and enteric pathogens, and list experimentally verified species of intestinal bacteria containing T6SS clusters. Several seminal studies have shown that T6SS plays crucial antibacterial roles in colonization resistance, niche occupancy, activation of host innate immune responses, and modulation of host intestinal mechanics. Some potential roles of T6SS in the intestinal ecosystem, such as targeting of single cell eukaryotic competitors, competition for micronutrients, and stress resistance are also discussed. Considering the distinct activities of T6SS in diverse bacteria residing in the intestine, we suggest that T6SS research in intestinal microbes may be beneficial for the future development of new medicines and clinical treatments.
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Affiliation(s)
- Can Chen
- Institute of Food and Drug Inspection, College of Life Science and Agronomy, Zhoukou Normal University, Zhoukou, China
| | - Xiaobing Yang
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
| | - Xihui Shen
- State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, China
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183
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Trunk K, Coulthurst SJ, Quinn J. A New Front in Microbial Warfare-Delivery of Antifungal Effectors by the Type VI Secretion System. J Fungi (Basel) 2019; 5:jof5020050. [PMID: 31197124 PMCID: PMC6617251 DOI: 10.3390/jof5020050] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2019] [Revised: 06/11/2019] [Accepted: 06/13/2019] [Indexed: 12/29/2022] Open
Abstract
Microbes typically exist in mixed communities and display complex synergistic and antagonistic interactions. The Type VI secretion system (T6SS) is widespread in Gram-negative bacteria and represents a contractile nano-machine that can fire effector proteins directly into neighbouring cells. The primary role assigned to the T6SS is to function as a potent weapon during inter-bacterial competition, delivering antibacterial effectors into rival bacterial cells. However, it has recently emerged that the T6SS can also be used as a powerful weapon against fungal competitors, and the first fungal-specific T6SS effector proteins, Tfe1 and Tfe2, have been identified. These effectors act via distinct mechanisms against a variety of fungal species to cause cell death. Tfe1 intoxication triggers plasma membrane depolarisation, whilst Tfe2 disrupts nutrient uptake and induces autophagy. Based on the frequent coexistence of bacteria and fungi in microbial communities, we propose that T6SS-dependent antifungal activity is likely to be widespread and elicited by a suite of antifungal effectors. Supporting this hypothesis, homologues of Tfe1 and Tfe2 are found in other bacterial species, and a number of T6SS-elaborating species have been demonstrated to interact with fungi. Thus, we envisage that antifungal T6SS will shape many polymicrobial communities, including the human microbiota and disease-causing infections.
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Affiliation(s)
- Katharina Trunk
- Institute for Cell and Molecular Biosciences, Faculty of Medicine, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
| | - Sarah J Coulthurst
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
| | - Janet Quinn
- Institute for Cell and Molecular Biosciences, Faculty of Medicine, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
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184
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Abstract
The symbiosis between Euprymna scolopes squid and its bioluminescent bacterial symbiont, Vibrio fischeri, is a valuable model system to study a natural, coevolved host-microbe association. Over the past 30 years, researchers have developed and optimized many experimental methods to study both partners in isolation and during symbiosis. The symbiosis between Euprymna scolopes squid and its bioluminescent bacterial symbiont, Vibrio fischeri, is a valuable model system to study a natural, coevolved host-microbe association. Over the past 30 years, researchers have developed and optimized many experimental methods to study both partners in isolation and during symbiosis. These powerful tools, along with a strong foundational knowledge about the system, position the Vibrio-squid symbiosis at the forefront of host-microbe interactions because this system is uniquely suited to investigation of symbiosis from both host and bacterial perspectives. Moreover, the ability to isolate and characterize different strains of V. fischeri has revealed exciting new insights about how different genotypes evolve to compete for a host niche, including deploying interbacterial weapons early during host colonization. This Perspective explores how interbacterial warfare influences the diversity and spatial structure of the symbiotic population, as well as the possible effects that intraspecific competition might have on the host.
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185
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Draft Genome Sequences of Type VI Secretion System-Encoding Vibrio fischeri Strains FQ-A001 and ES401. Microbiol Resour Announc 2019; 8:8/20/e00385-19. [PMID: 31097508 PMCID: PMC6522793 DOI: 10.1128/mra.00385-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The type VI secretion system (T6SS) facilitates lethal competition between bacteria through direct contact. Comparative genomics has facilitated the study of these systems in Vibrio fischeri, which colonizes the squid host Euprymna scolopes Here, we report the draft genome sequences of two lethal V. fischeri strains that encode the T6SS, FQ-A001 and ES401.
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