1
|
Otto SB, Servajean R, Lemopoulos A, Bitbol AF, Blokesch M. Interactions between pili affect the outcome of bacterial competition driven by the type VI secretion system. Curr Biol 2024; 34:2403-2417.e9. [PMID: 38749426 DOI: 10.1016/j.cub.2024.04.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 04/09/2024] [Accepted: 04/22/2024] [Indexed: 06/06/2024]
Abstract
The bacterial type VI secretion system (T6SS) is a widespread, kin-discriminatory weapon capable of shaping microbial communities. Due to the system's dependency on contact, cellular interactions can lead to either competition or kin protection. Cell-to-cell contact is often accomplished via surface-exposed type IV pili (T4Ps). In Vibrio cholerae, these T4Ps facilitate specific interactions when the bacteria colonize natural chitinous surfaces. However, it has remained unclear whether and, if so, how these interactions affect the bacterium's T6SS-mediated killing. In this study, we demonstrate that pilus-mediated interactions can be harnessed by T6SS-equipped V. cholerae to kill non-kin cells under liquid growth conditions. We also show that the naturally occurring diversity of pili determines the likelihood of cell-to-cell contact and, consequently, the extent of T6SS-mediated competition. To determine the factors that enable or hinder the T6SS's targeted reduction of competitors carrying pili, we developed a physics-grounded computational model for autoaggregation. Collectively, our research demonstrates that T4Ps involved in cell-to-cell contact can impose a selective burden when V. cholerae encounters non-kin cells that possess an active T6SS. Additionally, our study underscores the significance of T4P diversity in protecting closely related individuals from T6SS attacks through autoaggregation and spatial segregation.
Collapse
Affiliation(s)
- Simon B Otto
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Richard Servajean
- Laboratory of Computational Biology and Theoretical Biophysics, Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland; SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Alexandre Lemopoulos
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Anne-Florence Bitbol
- Laboratory of Computational Biology and Theoretical Biophysics, Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland; SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Melanie Blokesch
- Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
| |
Collapse
|
2
|
Sadhukhan S, Jacques MA, Potnis N. Influence of Co-occurring Weakly Pathogenic Bacterial Species on Bacterial Spot Disease Dynamics on Tomato. PLANT DISEASE 2024; 108:190-199. [PMID: 37537791 DOI: 10.1094/pdis-05-23-0837-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
Mixed infections caused by multiple pathogenic and weakly pathogenic strains inhabiting the same host plants are common in nature and may modify pathogen dynamics. However, traditional plant pathogen studies have mostly focused on the binary interaction between a single host and a single pathogen. In this study, we have looked beyond this binary interaction and evaluated the impact of coinfection on disease dynamics on tomato using the bacterial spot pathogen Xanthomonas perforans (Xp), the co-occurring weakly pathogenic strain of X. arboricola (Xa), and the co-occurring potential weak pathogenic strain of Pseudomonas capsici (Pc). Time-series coinfection experiments monitoring disease severity and within-host population dynamics revealed higher disease severity in coinfection by three species compared with infection by Xp alone. However, coinfection by dual species, Xp and Pc, or Xa resulted in lower disease severity compared with Xp alone. Thus, coinfection outcomes depend on interacting species. Weak pathogens could exploit Xp to colonize the host plant as indicated by their higher populations in coinfection. However, Xp population dynamics were dependent on the coinfecting partner. While resource competition might be a possible explanation for lower Xp population in dual coinfection, interaction of Pc with the host was found to influence Xp population. Interestingly, Xp population was higher in the presence of three-species interaction compared with Xp and Xa coinfection, suggesting potential modulation of cooperative interactions among Xp and Xa in three-species coinfection rather than competitive interactions. Humidity played a significant role in population dynamics of the three species. Overall, this study highlighted the importance of coinfection dynamics in studying plant disease outbreaks.
Collapse
Affiliation(s)
- Shreya Sadhukhan
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, U.S.A
| | | | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, U.S.A
| |
Collapse
|
3
|
Goffredi SK, Panossian B, Brzechffa C, Field N, King C, Moggioli G, Rouse GW, Martín-Durán JM, Henry LM. A dynamic epibiont community associated with the bone-eating polychaete genus Osedax. mBio 2023; 14:e0314022. [PMID: 37382438 PMCID: PMC10470745 DOI: 10.1128/mbio.03140-22] [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] [Received: 11/08/2022] [Accepted: 05/08/2023] [Indexed: 06/30/2023] Open
Abstract
Osedax, the deep-sea annelid found at sunken whalefalls, is known to host Oceanospirillales bacterial endosymbionts intracellularly in specialized roots, which help it feed exclusively on vertebrate bones. Past studies, however, have also made mention of external bacteria on their trunks. During a 14-yr study, we reveal a dynamic, yet persistent, shift of Campylobacterales integrated into the epidermis of Osedax, which change over time as the whale carcass degrades on the sea floor. The Campylobacterales associated with seven species of Osedax, which comprise 67% of the bacterial community on the trunk, appear initially dominated by the genus Arcobacter (at early time points <24 mo), the Sulfurospirillum at intermediate stages (~50 mo), and the Sulfurimonas at later stages (>140 mo) of whale carcass decomposition. Metagenome analysis of the epibiont metabolic capabilities suggests potential for a transition from heterotrophy to autotrophy and differences in their capacity to metabolize oxygen, carbon, nitrogen, and sulfur. Compared to free-living relatives, the Osedax epibiont genomes were enriched in transposable elements, implicating genetic exchange on the host surface, and contained numerous secretions systems with eukaryotic-like protein (ELP) domains, suggesting a long evolutionary history with these enigmatic, yet widely distributed deep-sea worms. IMPORTANCE Symbiotic associations are widespread in nature and we can expect to find them in every type of ecological niche. In the last twenty years, the myriad of functions, interactions and species comprising microbe-host associations has fueled a surge of interest and appreciation for symbiosis. During this 14-year study, we reveal a dynamic population of bacterial epibionts, integrated into the epidermis of 7 species of a deep-sea worm group that feeds exclusively on the remains of marine mammals. The bacterial genomes provide clues of a long evolutionary history with these enigmatic worms. On the host surface, they exchange genes and appear to undergo ecological succession, as the whale carcass habitat degrades over time, similar to what is observed for some free-living communities. These, and other annelid worms are important keystone species for diverse deep-sea environments, yet the role of attached external bacteria in supporting host health has received relatively little attention.
Collapse
Affiliation(s)
- Shana K. Goffredi
- Department of Biology, Occidental College, Los Angeles, California, USA
| | - Balig Panossian
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, United Kingdom
| | - Camille Brzechffa
- Department of Biology, Occidental College, Los Angeles, California, USA
| | - Naomi Field
- Department of Biology, Occidental College, Los Angeles, California, USA
| | - Chad King
- Monterey Bay National Marine Sanctuary, Monterey, California, USA
| | - Giacomo Moggioli
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, United Kingdom
| | - Greg W. Rouse
- Scripps Oceanography, University of California, La Jolla, California, USA
| | - José M. Martín-Durán
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, United Kingdom
| | - Lee M. Henry
- School of Biological and Behavioural Sciences, Queen Mary University of London, London, United Kingdom
| |
Collapse
|
4
|
Hespanhol JT, Nóbrega-Silva L, Bayer-Santos E. Regulation of type VI secretion systems at the transcriptional, posttranscriptional and posttranslational level. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001376. [PMID: 37552221 PMCID: PMC10482370 DOI: 10.1099/mic.0.001376] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/25/2023] [Indexed: 08/09/2023]
Abstract
Bacteria live in complex polymicrobial communities and are constantly competing for resources. The type VI secretion system (T6SS) is a widespread antagonistic mechanism used by Gram-negative bacteria to gain an advantage over competitors. T6SSs translocate toxic effector proteins inside target prokaryotic cells in a contact-dependent manner. In addition, some T6SS effectors can be secreted extracellularly and contribute to the scavenging scarce metal ions. Bacteria deploy their T6SSs in different situations, categorizing these systems into offensive, defensive and exploitative. The great variety of bacterial species and environments occupied by such species reflect the complexity of regulatory signals and networks that control the expression and activation of the T6SSs. Such regulation is tightly controlled at the transcriptional, posttranscriptional and posttranslational level by abiotic (e.g. pH, iron) or biotic (e.g. quorum-sensing) cues. In this review, we provide an update on the current knowledge about the regulatory networks that modulate the expression and activity of T6SSs across several species, focusing on systems used for interbacterial competition.
Collapse
Affiliation(s)
- Julia Takuno Hespanhol
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Luize Nóbrega-Silva
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| | - Ethel Bayer-Santos
- Department of Microbiology, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo 05508-900, Brazil
| |
Collapse
|
5
|
Lin YL, Smith SN, Kanso E, Septer AN, Rycroft CH. A subcellular biochemical model for T6SS dynamics reveals winning competitive strategies. PNAS NEXUS 2023; 2:pgad195. [PMID: 37441614 PMCID: PMC10335733 DOI: 10.1093/pnasnexus/pgad195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 05/30/2023] [Accepted: 06/01/2023] [Indexed: 07/15/2023]
Abstract
The type VI secretion system (T6SS) is a broadly distributed interbacterial weapon that can be used to eliminate competing bacterial populations. Although unarmed target populations are typically used to study T6SS function in vitro, bacteria most likely encounter other T6SS-armed competitors in nature. However, the connection between subcellular details of the T6SS and the outcomes of such mutually lethal battles is not well understood. Here, we incorporate biological data derived from natural competitors of Vibrio fischeri light organ symbionts to build a biochemical model for T6SS at the single-cell level, which we then integrate into an agent-based model (ABM). Using the ABM, we isolate and experiment with strain-specific physiological differences between competitors in ways not possible with biological samples to identify winning strategies for T6SS-armed populations. Through in vitro experiments, we discover that strain-specific differences exist in T6SS activation speed. ABM simulations corroborate that faster activation is dominant in determining survival during competition. Once competitors are fully activated, the energy required for T6SS creates a tipping point where increased weapon building and firing becomes too costly to be advantageous. Through ABM simulations, we identify the threshold where this transition occurs in the T6SS parameter space. We also find that competitive outcomes depend on the geometry of the battlefield: unarmed target cells survive at the edges of a range expansion where unlimited territory can be claimed. Alternatively, competitions within a confined space, much like the light organ crypts where natural V. fischeri compete, result in the rapid elimination of the unarmed population.
Collapse
Affiliation(s)
| | | | - Eva Kanso
- Department of Aerospace and Mechanical Engineering, University of Southern California, 3650 McClintock Ave, Los Angeles, CA 90089, USA
| | | | | |
Collapse
|
6
|
Septer AN, Sharpe G, Shook EA. The Vibrio fischeri type VI secretion system incurs a fitness cost under host-like conditions. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.07.529561. [PMID: 36945377 PMCID: PMC10028907 DOI: 10.1101/2023.03.07.529561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
The type VI secretion system (T6SS) is an interbacterial weapon composed of thousands of protein subunits and predicted to require significant cellular energy to deploy, yet a fitness cost from T6SS use is rarely observed. Here, we identify host-like conditions where the T6SS incurs a fitness cost using the beneficial symbiont, Vibrio fischeri, which uses its T6SS to eliminate competitors in the natural squid host. We hypothesized that a fitness cost for the T6SS could be dependent on the cellular energetic state and used theoretical ATP cost estimates to predict when a T6SS-dependent fitness cost may be apparent. Theoretical energetic cost estimates predicted a minor relative cost for T6SS use in fast-growing populations (0.4-0.45% of total ATP used cell-1), and a higher relative cost (3.1-13.6%) for stationary phase cells. Consistent with these predictions, we observed no significant T6SS-dependent fitness cost for fast-growing populations typically used for competition assays. However, the stationary phase cell density was significantly lower in the wild-type strain, compared to a regulator mutant that does not express the T6SS, and this T6SS-dependent fitness cost was between 11 and 23%. Such a fitness cost could influence the prevalence and biogeography of T6SSs in animal-associated bacteria. While the T6SS may be required in kill or be killed scenarios, once the competitor is eliminated there is no longer selective pressure to maintain the weapon. Our findings indicate an evolved genotype lacking the T6SS would have a growth advantage over its parent, resulting in the eventual dominance of the unarmed population.
Collapse
Affiliation(s)
- Alecia N. Septer
- Department of Earth, Marine & Environmental Sciences, University of North Carolina, Chapel Hill, NC 27599
| | - Garrett Sharpe
- Department of Earth, Marine & Environmental Sciences, University of North Carolina, Chapel Hill, NC 27599
- Environment, Ecology & Energy Program, University of North Carolina, Chapel Hill, NC 27599
| | - Erika A. Shook
- Department of Earth, Marine & Environmental Sciences, University of North Carolina, Chapel Hill, NC 27599
| |
Collapse
|
7
|
Type VI Secretion Systems: Environmental and Intra-host Competition of Vibrio cholerae. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1404:41-63. [PMID: 36792870 DOI: 10.1007/978-3-031-22997-8_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The Vibrio Type VI Secretion System (T6SS) is a harpoon-like nanomachine that serves as a defense system and is encoded by approximately 25% of all gram-negative bacteria. In this chapter, we describe the structure of the T6SS in different Vibrio species and outline how the use of different T6SS effector and immunity proteins control kin selection. We summarize the genetic loci that encode the structural elements that make up the Vibrio T6SSs and how these gene clusters are regulated. Finally, we provide insights into T6SS-based competitive dynamics, the role of T6SS genetic exchange in those competitive dynamics, and roles for the Vibrio T6SS in virulence.
Collapse
|
8
|
Guckes KR, Miyashiro TI. The type-VI secretion system of the beneficial symbiont Vibrio fischeri. MICROBIOLOGY (READING, ENGLAND) 2023; 169:10.1099/mic.0.001302. [PMID: 36809081 PMCID: PMC9972734 DOI: 10.1099/mic.0.001302] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The mutualistic symbiosis between the Hawaiian bobtail squid Euprymna scolopes and the marine bacterium Vibrio fischeri is a powerful experimental system for determining how intercellular interactions impact animal-bacterial associations. In nature, this symbiosis features multiple strains of V. fischeri within each adult animal, which indicates that different strains initially colonize each squid. Various studies have demonstrated that certain strains of V. fischeri possess a type-VI secretion system (T6SS), which can inhibit other strains from establishing symbiosis within the same host habitat. The T6SS is a bacterial melee weapon that enables a cell to kill adjacent cells by translocating toxic effectors via a lancet-like apparatus. This review describes the progress that has been made in understanding the factors that govern the structure and expression of the T6SS in V. fischeri and its effect on the symbiosis.
Collapse
|
9
|
Doty SL, Joubert PM, Firrincieli A, Sher AW, Tournay R, Kill C, Parikh SS, Okubara P. Potential Biocontrol Activities of Populus Endophytes against Several Plant Pathogens Using Different Inhibitory Mechanisms. Pathogens 2022; 12:pathogens12010013. [PMID: 36678361 PMCID: PMC9862643 DOI: 10.3390/pathogens12010013] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/17/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022] Open
Abstract
The plant microbiome can be used to bolster plant defense against abiotic and biotic stresses. Some strains of endophytes, the microorganisms within plants, can directly inhibit the growth of plant fungal pathogens. A previously isolated endophyte from wild Populus (poplar), WPB of the species Burkholderia vietnamiensis, had robust in vitro antifungal activity against pathogen strains that are highly virulent and of concern to Pacific Northwest agriculture: Rhizoctonia solani AG-8, Fusarium culmorum 70110023, and Gaemannomyces graminis var. tritici (Ggt) ARS-A1, as well as activity against the oomycete, Pythium ultimum 217. A direct screening method was developed for isolation of additional anti-fungal endophytes from wild poplar extracts. By challenging pathogens directly with dilute extracts, eleven isolates were found to be inhibitory to at least two plant pathogen strains and were therefore chosen for further characterization. Genomic analysis was conducted to determine if these endophyte strains harbored genes known to be involved in antimicrobial activities. The newly isolated Bacillus strains had gene clusters for production of bacillomycin, fengicyn, and bacillibactin, while the gene cluster for the synthesis of sessilin, viscosin and tolaasin were found in the Pseudomonas strains. The biosynthesis gene cluster for occidiofungin (ocf) was present in the Burkholderia vietnamiensis WPB genome, and an ocf deletion mutant lost inhibitory activity against 3 of the 4 pathogens. The new isolates lacked the gene cluster for occidiofungin implying they employ different modes of action. Other symbiotic traits including nitrogen fixation, phosphate solubilization, and the production of auxins and siderophores were investigated. Although it will be necessary to conduct in vivo tests of the candidates with pathogen-infected agricultural crops, the wild poplar tree microbiome may be a rich source of beneficial endophyte strains with potential for biocontrol applications against a variety of pathogens and utilizing varying modes of action.
Collapse
Affiliation(s)
- Sharon L. Doty
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
- Correspondence:
| | - Pierre M. Joubert
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
- Department of Plant & Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - Andrea Firrincieli
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
- Department for Innovation in Biological, Agro-Food and Forest Systems, University of Tuscia, 01100 Viterbo, Italy
| | - Andrew W. Sher
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
| | - Robert Tournay
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
| | - Carina Kill
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
- Native Roots School, Taos, NM 87571, USA
| | - Shruti S. Parikh
- School of Environmental and Forest Sciences, College of the Environment, University of Washington, Seattle, WA 98195, USA
- Department of Food Science and Technology, University of California, Davis, CA 95616, USA
| | - Patricia Okubara
- Department of Plant Pathology, Washington State University, Pullman, WA 99164, USA
| |
Collapse
|
10
|
Speare L, Jackson A, Septer AN. Calcium Promotes T6SS-Mediated Killing and Aggregation between Competing Symbionts. Microbiol Spectr 2022; 10:e0139722. [PMID: 36453912 PMCID: PMC9769598 DOI: 10.1128/spectrum.01397-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Accepted: 11/05/2022] [Indexed: 12/03/2022] Open
Abstract
Bacteria use a variety of strategies to exclude competitors from accessing resources, including space within a host niche. Because these mechanisms are typically costly to deploy, they are often tightly regulated for use in environments where the benefits outweigh the energetic cost. The type VI secretion system (T6SS) is a competitive mechanism that allows inhibitors to kill competing microbes by physically puncturing and translocating cytotoxic effectors directly into neighboring competitor cells. Although T6SSs are encoded in both symbiotic and free-living taxa where they may be actively secreting into the extracellular milieu during growth in liquid culture, there is little evidence for bacteria engaging in T6SS-mediated, contact-dependent killing under low-viscosity liquid conditions. Here, we determined that calcium acts as a pH-dependent cue to activate the assembly of an antibacterial T6SS in a Vibrio fischeri light organ symbiont in a low-viscosity liquid medium. Moreover, competing V. fischeri isolates formed mixed-strain aggregates that promoted the contact necessary for T6SS-dependent elimination of a target population. Our findings expand our knowledge of V. fischeri T6SS ecology and identify a low-viscosity liquid condition where cells engage in contact-dependent killing. IMPORTANCE Microbes deploy competitive mechanisms to gain access to resources such as nutrients or space within an ecological niche. Identifying when and where these strategies are employed can be challenging given the complexity and variability of most natural systems; therefore, studies evaluating specific cues that conditionally regulate interbacterial competition can inform the ecological context for such competition. In this work, we identified a pH-dependent chemical cue in seawater, calcium, which promotes activation of a contact-dependent interbacterial weapon in the marine symbiont Vibrio fischeri. This finding underscores the importance of using ecologically relevant salts in growth media and the ability of bacterial cells to sense and integrate multiple environmental cues to assess the need for a weapon. Identification of these cues provides insight into the types of environments where employing a weapon is advantageous to the survival and propagation of a bacterial population.
Collapse
Affiliation(s)
- Lauren Speare
- Department of Earth, Marine & Environmental Sciences, University of North Carolina, Chapel Hill, North Carolina, USA
- Department of Microbiology, Oregon State University, Corvallis, Oregon, USA
| | - Aundre Jackson
- Department of Earth, Marine & Environmental Sciences, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Alecia N. Septer
- Department of Earth, Marine & Environmental Sciences, University of North Carolina, Chapel Hill, North Carolina, USA
| |
Collapse
|
11
|
A Putative Lipoprotein Mediates Cell-Cell Contact for Type VI Secretion System-Dependent Killing of Specific Competitors. mBio 2022; 13:e0308521. [PMID: 35404117 PMCID: PMC9040878 DOI: 10.1128/mbio.03085-21] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Interbacterial competition is prevalent in host-associated microbiota, where it can shape community structure and function, impacting host health in both positive and negative ways. However, the factors that permit bacteria to discriminate among their various neighbors for targeted elimination of competitors remain elusive. We identified a putative lipoprotein (TasL) in Vibrio species that mediates cell-cell attachment with a subset of target strains, allowing inhibitors to target specific competitors for elimination. Here, we describe this putative lipoprotein, which is associated with the broadly distributed type VI secretion system (T6SS), by studying symbiotic Vibrio fischeri, which uses the T6SS to compete for colonization sites in their squid host. We demonstrate that TasL allows V. fischeri cells to restrict T6SS-dependent killing to certain genotypes by selectively integrating competitor cells into aggregates while excluding other cell types. TasL is also required for T6SS-dependent competition within juvenile squid, indicating that the adhesion factor is active in the host. Because TasL homologs are found in other host-associated bacterial species, this newly described cell-cell attachment mechanism has the potential to impact microbiome structure within diverse hosts. IMPORTANCE T6SSs are broadly distributed interbacterial weapons that share an evolutionary history with bacteriophage. Because the T6SS can be used to kill neighboring cells, it can impact the spatial distribution and biological function of both free-living and host-associated microbial communities. Like their phage relatives, T6SS+ cells must sufficiently bind competitor cells to deliver their toxic effector proteins through the syringe-like apparatus. Although phage use receptor-binding proteins (RBPs) and tail fibers to selectively bind prey cells, the biophysical properties that mediate this cell-cell contact for T6SS-mediated killing remain unknown. Here, we identified a large, predicted lipoprotein that is coordinately expressed with T6SS proteins and facilitates the contact that is necessary for the T6SS-dependent elimination of competitors in a natural host. Similar to phage RBPs and tail fibers, this lipoprotein is required for T6SS+ cells to discriminate between prey and nonprey cell types, revealing new insight into prey selection during T6SS-mediated competition.
Collapse
|
12
|
Avelino-Flores F, Soria-Bustos J, Saldaña-Ahuactzi Z, Martínez-Laguna Y, Yañez-Santos JA, Cedillo-Ramírez ML, Girón JA. The Transcription of Flagella of Enteropathogenic Escherichia coli O127:H6 Is Activated in Response to Environmental and Nutritional Signals. Microorganisms 2022; 10:microorganisms10040792. [PMID: 35456842 PMCID: PMC9032864 DOI: 10.3390/microorganisms10040792] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 03/23/2022] [Accepted: 03/23/2022] [Indexed: 02/01/2023] Open
Abstract
The flagella of enteropathogenic Escherichia coli (EPEC) O127:H6 E2348/69 mediate adherence to host proteins and epithelial cells. What environmental and nutritional signals trigger or down-regulate flagella expression in EPEC are largely unknown. In this study, we analyzed the influence of pH, oxygen tension, cationic and anionic salts (including bile salt), carbon and nitrogen sources, and catecholamines on the expression of the flagellin gene (fliC) of E2348/69. We found that sodium bicarbonate, which has been shown to induce the expression of type III secretion effectors, down-regulated flagella expression, explaining why E2348/69 shows reduced motility and flagellation when growing in Dulbecco’s Minimal Essential Medium (DMEM). Further, growth under a 5% carbon dioxide atmosphere, in DMEM adjusted to pH 8.2, in M9 minimal medium supplemented with 80 mM glucose or sucrose, and in DMEM containing 150 mM sodium chloride, 0.1% sodium deoxycholate, or 30 µM epinephrine significantly enhanced fliC transcription to different levels in comparison to growth in DMEM alone. When EPEC was grown in the presence of HeLa cells or in supernatants of cultured HeLa cells, high levels (4-fold increase) of fliC transcription were detected in comparison to growth in DMEM alone. Our data suggest that nutritional and host signals that EPEC may encounter in the intestinal niche activate fliC expression in order to favor motility and host colonization.
Collapse
Affiliation(s)
- Fabiola Avelino-Flores
- Centro de Investigación en Ciencias Microbiológicas, Benemérita Universidad Autónoma de Puebla, Puebla 72570, Mexico; (F.A.-F.); (Y.M.-L.)
| | - Jorge Soria-Bustos
- Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca 42160, Mexico;
| | - Zeus Saldaña-Ahuactzi
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA;
| | - Ygnacio Martínez-Laguna
- Centro de Investigación en Ciencias Microbiológicas, Benemérita Universidad Autónoma de Puebla, Puebla 72570, Mexico; (F.A.-F.); (Y.M.-L.)
| | - Jorge A. Yañez-Santos
- Facultad de Estomatología, Benemérita Universidad Autónoma de Puebla, Puebla 72410, Mexico;
| | - María L. Cedillo-Ramírez
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla 72592, Mexico;
| | - Jorge A. Girón
- Centro de Detección Biomolecular, Benemérita Universidad Autónoma de Puebla, Puebla 72592, Mexico;
- Correspondence:
| |
Collapse
|
13
|
Nocturnal Acidification: A Coordinating Cue in the Euprymna scolopes- Vibrio fischeri Symbiosis. Int J Mol Sci 2022; 23:ijms23073743. [PMID: 35409100 PMCID: PMC8999011 DOI: 10.3390/ijms23073743] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 03/23/2022] [Accepted: 03/24/2022] [Indexed: 01/27/2023] Open
Abstract
The Vibrio fischeri–Euprymna scolopes symbiosis has become a powerful model for the study of specificity, initiation, and maintenance between beneficial bacteria and their eukaryotic partner. In this invertebrate model system, the bacterial symbionts are acquired every generation from the surrounding seawater by newly hatched squid. These symbionts colonize a specialized internal structure called the light organ, which they inhabit for the remainder of the host’s lifetime. The V. fischeri population grows and ebbs following a diel cycle, with high cell densities at night producing bioluminescence that helps the host avoid predation during its nocturnal activities. Rhythmic timing of the growth of the symbionts and their production of bioluminescence only at night is critical for maintaining the symbiosis. V. fischeri symbionts detect their population densities through a behavior termed quorum-sensing, where they secrete and detect concentrations of autoinducer molecules at high cell density when nocturnal production of bioluminescence begins. In this review, we discuss events that lead up to the nocturnal acidification of the light organ and the cues used for pre-adaptive behaviors that both host and symbiont have evolved. This host–bacterium cross talk is used to coordinate networks of regulatory signals (such as quorum-sensing and bioluminescence) that eventually provide a unique yet stable environment for V. fischeri to thrive and be maintained throughout its life history as a successful partner in this dynamic symbiosis.
Collapse
|