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Septer AN, Visick KL. Lighting the way: how the Vibrio fischeri model microbe reveals the complexity of Earth's "simplest" life forms. J Bacteriol 2024; 206:e0003524. [PMID: 38695522 PMCID: PMC11112999 DOI: 10.1128/jb.00035-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2024] Open
Abstract
Vibrio (Aliivibrio) fischeri's initial rise to fame derived from its alluring production of blue-green light. Subsequent studies to probe the mechanisms underlying this bioluminescence helped the field discover the phenomenon now known as quorum sensing. Orthologs of quorum-sensing regulators (i.e., LuxR and LuxI) originally identified in V. fischeri were subsequently uncovered in a plethora of bacterial species, and analogous pathways were found in yet others. Over the past three decades, the study of this microbe has greatly expanded to probe the unique role of V. fischeri as the exclusive symbiont of the light organ of the Hawaiian bobtail squid, Euprymna scolopes. Buoyed by this optically amenable host and by persistent and insightful researchers who have applied novel and cross-disciplinary approaches, V. fischeri has developed into a robust model for microbe-host associations. It has contributed to our understanding of how bacteria experience and respond to specific, often fluxing environmental conditions and the mechanisms by which bacteria impact the development of their host. It has also deepened our understanding of numerous microbial processes such as motility and chemotaxis, biofilm formation and dispersal, and bacterial competition, and of the relevance of specific bacterial genes in the context of colonizing an animal host. Parallels in these processes between this symbiont and bacteria studied as pathogens are readily apparent, demonstrating functional conservation across diverse associations and permitting a reinterpretation of "pathogenesis." Collectively, these advances built a foundation for microbiome studies and have positioned V. fischeri to continue to expand the frontiers of our understanding of the microbial world inside animals.
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Affiliation(s)
- Alecia N. Septer
- Department of Earth, Marine and Environmental Sciences, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Karen L. Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
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2
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Fung BL, Esin JJ, Visick KL. Vibrio fischeri: a model for host-associated biofilm formation. J Bacteriol 2024; 206:e0037023. [PMID: 38270381 PMCID: PMC10882983 DOI: 10.1128/jb.00370-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024] Open
Abstract
Multicellular communities of adherent bacteria known as biofilms are often detrimental in the context of a human host, making it important to study their formation and dispersal, especially in animal models. One such model is the symbiosis between the squid Euprymna scolopes and the bacterium Vibrio fischeri. Juvenile squid hatch aposymbiotically and selectively acquire their symbiont from natural seawater containing diverse environmental microbes. Successful pairing is facilitated by ciliary movements that direct bacteria to quiet zones on the surface of the squid's symbiotic light organ where V. fischeri forms a small aggregate or biofilm. Subsequently, the bacteria disperse from that aggregate to enter the organ, ultimately reaching and colonizing deep crypt spaces. Although transient, aggregate formation is critical for optimal colonization and is tightly controlled. In vitro studies have identified a variety of polysaccharides and proteins that comprise the extracellular matrix. Some of the most well-characterized matrix factors include the symbiosis polysaccharide (SYP), cellulose polysaccharide, and LapV adhesin. In this review, we discuss these components, their regulation, and other less understood V. fischeri biofilm contributors. We also highlight what is currently known about dispersal from these aggregates and host cues that may promote it. Finally, we briefly describe discoveries gleaned from the study of other V. fischeri isolates. By unraveling the complexities involved in V. fischeri's control over matrix components, we may begin to understand how the host environment triggers transient biofilm formation and dispersal to promote this unique symbiotic relationship.
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Affiliation(s)
- Brittany L. Fung
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Jeremy J. Esin
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Karen L. Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
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3
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Baden T, Briseño J, Coffing G, Cohen-Bodénès S, Courtney A, Dickerson D, Dölen G, Fiorito G, Gestal C, Gustafson T, Heath-Heckman E, Hua Q, Imperadore P, Kimbara R, Król M, Lajbner Z, Lichilín N, Macchi F, McCoy MJ, Nishiguchi MK, Nyholm SV, Otjacques E, Pérez-Ferrer PA, Ponte G, Pungor JR, Rogers TF, Rosenthal JJC, Rouressol L, Rubas N, Sanchez G, Santos CP, Schultz DT, Seuntjens E, Songco-Casey JO, Stewart IE, Styfhals R, Tuanapaya S, Vijayan N, Weissenbacher A, Zifcakova L, Schulz G, Weertman W, Simakov O, Albertin CB. Cephalopod-omics: Emerging Fields and Technologies in Cephalopod Biology. Integr Comp Biol 2023; 63:1226-1239. [PMID: 37370232 PMCID: PMC10755191 DOI: 10.1093/icb/icad087] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 06/09/2023] [Accepted: 06/13/2023] [Indexed: 06/29/2023] Open
Abstract
Few animal groups can claim the level of wonder that cephalopods instill in the minds of researchers and the general public. Much of cephalopod biology, however, remains unexplored: the largest invertebrate brain, difficult husbandry conditions, and complex (meta-)genomes, among many other things, have hindered progress in addressing key questions. However, recent technological advancements in sequencing, imaging, and genetic manipulation have opened new avenues for exploring the biology of these extraordinary animals. The cephalopod molecular biology community is thus experiencing a large influx of researchers, emerging from different fields, accelerating the pace of research in this clade. In the first post-pandemic event at the Cephalopod International Advisory Council (CIAC) conference in April 2022, over 40 participants from all over the world met and discussed key challenges and perspectives for current cephalopod molecular biology and evolution. Our particular focus was on the fields of comparative and regulatory genomics, gene manipulation, single-cell transcriptomics, metagenomics, and microbial interactions. This article is a result of this joint effort, summarizing the latest insights from these emerging fields, their bottlenecks, and potential solutions. The article highlights the interdisciplinary nature of the cephalopod-omics community and provides an emphasis on continuous consolidation of efforts and collaboration in this rapidly evolving field.
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Affiliation(s)
- Tom Baden
- School of Life Sciences, University of Sussex, Brighton BN1 9QG, UK
| | - John Briseño
- Molecular and Cell Biology Department, University of Connecticut, Storrs, CT 06269, USA
| | - Gabrielle Coffing
- Biology Department: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403-5289, USA
| | - Sophie Cohen-Bodénès
- Laboratoire des Systèmes Perceptifs, Département d'Etudes Cognitives, Ecole Normale Supérieure, PSL University, CNRS, 75005 Paris, France
| | - Amy Courtney
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Dominick Dickerson
- Friday Harbor Laboratory, University of Washington, Seattle, WA 98250, USA
| | - Gül Dölen
- Department of Neuroscience, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Graziano Fiorito
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, 80121 Napoli, Italy
| | - Camino Gestal
- Laboratory of Marine Molecular Pathobiology, Institute of Marine Research (IIM), Spanish National Research Council (CSIC), Vigo 36208, Spain
| | | | - Elizabeth Heath-Heckman
- Departments of Integrative Biology and Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Qiaz Hua
- Department of Ecology and Evolution, University of Adelaide, Adelaide, South Australia 5000, Australia
| | - Pamela Imperadore
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, 80121 Napoli, Italy
| | - Ryosuke Kimbara
- Misaki Marine Biological Station, School of Science, The University of Tokyo, Miura, Kanagawa 238-0225, Japan
| | - Mirela Król
- Adam Mickiewicz University in Poznań, Poznań 61-712, Poland
| | - Zdeněk Lajbner
- Physics and Biology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | - Nicolás Lichilín
- Department of Neurosciences and Developmental Biology, University of Vienna, Vienna 1010, Austria
| | - Filippo Macchi
- Program in Biology, New York University Abu Dhabi, P.O. Box 129188 Abu Dhabi, United Arab Emirates
| | - Matthew J McCoy
- Department of Pathology, Stanford University, Stanford, CA 94305, USA
| | - Michele K Nishiguchi
- Department of Molecular and Cell Biology, School of Natural Sciences, University of California, Merced, 5200 N. Lake Blvd., Merced, CA 95343, USA
| | - Spencer V Nyholm
- Molecular and Cell Biology Department, University of Connecticut, Storrs, CT 06269, USA
| | - Eve Otjacques
- MARE—Marine and Environmental Sciences Centre & ARNET—Aquatic Research Network, Laboratório Marítimo da Guia, Faculdade de Ciências, Universidade de Lisboa, Av. Nossa Senhora do Cabo, 939, 2750-374 Cascais, Portugal
- Division of Biosphere Sciences and Engineering, Carnegie Institution for Science, 1200 E. California Blvd, Pasadena, CA 91125, USA
| | - Pedro Antonio Pérez-Ferrer
- Department of Molecular and Cell Biology, School of Natural Sciences, University of California, Merced, 5200 N. Lake Blvd., Merced, CA 95343, USA
| | - Giovanna Ponte
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, 80121 Napoli, Italy
| | - Judit R Pungor
- Biology Department: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403-5289, USA
| | - Thea F Rogers
- Department of Neurosciences and Developmental Biology, University of Vienna, Vienna 1010, Austria
| | - Joshua J C Rosenthal
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543-1015, USA
| | - Lisa Rouressol
- Department of Neurosciences and Developmental Biology, University of Vienna, Vienna 1010, Austria
| | - Noelle Rubas
- Department of Molecular Biosciences and Bioengineering, University of Hawaii Manoa, Honolulu, HI 96822, USA
| | - Gustavo Sanchez
- Molecular Genetics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan
| | - Catarina Pereira Santos
- MARE—Marine and Environmental Sciences Centre & ARNET—Aquatic Research Network, Laboratório Marítimo da Guia, Faculdade de Ciências, Universidade de Lisboa, Av. Nossa Senhora do Cabo, 939, 2750-374 Cascais, Portugal
| | - Darrin T Schultz
- Department of Neurosciences and Developmental Biology, University of Vienna, Vienna 1010, Austria
| | - Eve Seuntjens
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven 3000, Belgium
| | - Jeremea O Songco-Casey
- Biology Department: Institute of Ecology and Evolution, University of Oregon, Eugene, OR 97403-5289, USA
| | - Ian Erik Stewart
- Neural Circuits and Behaviour Lab, Max‐Delbrück‐Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin 13125, Germany
| | - Ruth Styfhals
- Laboratory of Developmental Neurobiology, Department of Biology, KU Leuven, Leuven 3000, Belgium
| | - Surangkana Tuanapaya
- Laboratory of genetics and applied breeding of molluscs, Fisheries College, Ocean University of China, Qingdao 266100, China
| | - Nidhi Vijayan
- Molecular and Cell Biology Department, University of Connecticut, Storrs, CT 06269, USA
| | | | - Lucia Zifcakova
- Physics and Biology Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Kunigami District, Okinawa 904-0495, Japan
| | | | - Willem Weertman
- Friday Harbor Laboratory, University of Washington, Seattle, WA 98250, USA
| | - Oleg Simakov
- Department of Neurosciences and Developmental Biology, University of Vienna, Vienna 1010, Austria
| | - Caroline B Albertin
- Marine Biological Laboratory, The Eugene Bell Center for Regenerative Biology and Tissue Engineering, Woods Hole, MA 02543-1015, USA
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4
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Bongrand C, Foster JS. Modelled microgravity impacts Vibrio fischeri population structure in a mutualistic association with an animal host. Environ Microbiol 2023; 25:3269-3279. [PMID: 37828645 DOI: 10.1111/1462-2920.16522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 09/28/2023] [Indexed: 10/14/2023]
Abstract
Perturbations to host-microbe interactions, such as environmental stress, can alter and disrupt homeostasis. In this study, we examined the effects of a stressor, simulated microgravity, on beneficial bacteria behaviours when colonising their host. We studied the bacterium Vibrio fischeri, which establishes a mutualistic association in a symbiosis-specific organ within the bobtail squid, Euprymna scolopes. To elucidate how animal-microbe interactions are affected by the stress of microgravity, squid were inoculated with different bacterial strains exhibiting either a dominant- or sharing-colonisation behaviour in High Aspect Ratio Vessels, which simulate the low-shear environment of microgravity. The colonisation behaviours of the sharing and dominant strains under modelled microgravity conditions were determined by counting light-organ homogenate of squids as well as confocal microscopy to assess the partitioning of different strains within the light organ. The results indicated that although the colonisation behaviours of the strains did not change, the population levels of the sharing strains were at lower relative abundance in single-colonised animals exposed to modelled microgravity compared to unit gravity; in addition, there were shifts in the relative abundance of strains in co-colonised squids. Together these results suggest that the initiation of beneficial interactions between microbes and animals can be altered by environmental stress, such as simulated microgravity.
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Affiliation(s)
- Clotilde Bongrand
- Department of Microbiology and Cell Science, Space Life Sciences Lab, University of Florida, Merritt Island, Florida, USA
| | - Jamie S Foster
- Department of Microbiology and Cell Science, Space Life Sciences Lab, University of Florida, Merritt Island, Florida, USA
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Papudeshi B, Rusch DB, VanInsberghe D, Lively CM, Edwards RA, Bashey F. Host Association and Spatial Proximity Shape but Do Not Constrain Population Structure in the Mutualistic Symbiont Xenorhabdus bovienii. mBio 2023:e0043423. [PMID: 37154562 DOI: 10.1128/mbio.00434-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023] Open
Abstract
To what extent are generalist species cohesive evolutionary units rather than a compilation of recently diverged lineages? We examine this question in the context of host specificity and geographic structure in the insect pathogen and nematode mutualist Xenorhabdus bovienii. This bacterial species partners with multiple nematode species across two clades in the genus Steinernema. We sequenced the genomes of 42 X. bovienii strains isolated from four different nematode species and three field sites within a 240-km2 region and compared them to globally available reference genomes. We hypothesized that X. bovienii would comprise several host-specific lineages, such that bacterial and nematode phylogenies would be largely congruent. Alternatively, we hypothesized that spatial proximity might be a dominant signal, as increasing geographic distance might lower shared selective pressures and opportunities for gene flow. We found partial support for both hypotheses. Isolates clustered largely by nematode host species but did not strictly match the nematode phylogeny, indicating that shifts in symbiont associations across nematode species and clades have occurred. Furthermore, both genetic similarity and gene flow decreased with geographic distance across nematode species, suggesting differentiation and constraints on gene flow across both factors, although no absolute barriers to gene flow were observed across the regional isolates. Several genes associated with biotic interactions were found to be undergoing selective sweeps within this regional population. The interactions included several insect toxins and genes implicated in microbial competition. Thus, gene flow maintains cohesiveness across host associations in this symbiont and may facilitate adaptive responses to a multipartite selective environment. IMPORTANCE Microbial populations and species are notoriously hard to delineate. We used a population genomics approach to examine the population structure and the spatial scale of gene flow in Xenorhabdus bovienii, an intriguing species that is both a specialized mutualistic symbiont of nematodes and a broadly virulent insect pathogen. We found a strong signature of nematode host association, as well as evidence for gene flow connecting isolates associated with different nematode host species and collected from distinct study sites. Furthermore, we saw signatures of selective sweeps for genes involved with nematode host associations, insect pathogenicity, and microbial competition. Thus, X. bovienii exemplifies the growing consensus that recombination not only maintains cohesion but can also allow the spread of niche-beneficial alleles.
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Affiliation(s)
- Bhavya Papudeshi
- Flinders Accelerator for Microbiome Exploration, Flinders University, Adelaide, Australia
- National Centre for Genome Analysis Support, Pervasive Institute of Technology, Indiana University, Bloomington, Indiana, USA
| | - Douglas B Rusch
- Center for Genomics and Bioinformatics, Indiana University, Bloomington, Indiana, USA
| | | | - Curtis M Lively
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Robert A Edwards
- Flinders Accelerator for Microbiome Exploration, Flinders University, Adelaide, Australia
| | - Farrah Bashey
- Department of Biology, Indiana University, Bloomington, Indiana, USA
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6
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Park J, Davis K, Lajoie G, Parfrey LW. Alternative approaches to identify core bacteria in Fucus distichus microbiome and assess their distribution and host-specificity. ENVIRONMENTAL MICROBIOME 2022; 17:55. [PMID: 36384808 PMCID: PMC9670562 DOI: 10.1186/s40793-022-00451-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 11/09/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND Identifying meaningful ecological associations between host and components of the microbiome is challenging. This is especially true for hosts such as marine macroalgae where the taxonomic composition of the microbiome is highly diverse and variable in space and time. Identifying core taxa is one way forward but there are many methods and thresholds in use. This study leverages a large dataset of microbial communities associated with the widespread brown macroalga, Fucus distichus, across sites and years on one island in British Columbia, Canada. We compare three different methodological approaches to identify core taxa at the amplicon sequence variant (ASV) level from this dataset: (1) frequency analysis of taxa on F. distichus performed over the whole dataset, (2) indicator species analysis (IndVal) over the whole dataset that identifies frequent taxa that are enriched on F. distichus in comparison to the local environment, and (3) a two-step IndVal method that identifies taxa that are consistently enriched on F. distichus across sites and time points. We then investigated a F. distichus time-series dataset to see if those core taxa are seasonally consistent on another remote island in British Columbia, Canada. We then evaluate host-specificity of the identified F. distichus core ASVs using comparative data from 32 other macroalgal species sampled at one of the sites. RESULTS We show that a handful of core ASVs are consistently identified by both frequency analysis and IndVal approaches with alternative definitions, although no ASVs were always present on F. distichus and IndVal identified a diverse array of F. distichus indicator taxa across sites on Calvert Island in multiple years. Frequency analysis captured a broader suit of taxa, while IndVal was better at identifying host-specific microbes. Finally, two-step IndVal identified hundreds of indicator ASVs for particular sites/timepoints but only 12 that were indicators in a majority (> 6 out of 11) of sites/timepoints. Ten of these ASVs were also indicators on Quadra Island, 250 km away. Many F. distichus-core ASVs are generally found on multiple macroalgal species, while a few ASVs are highly specific to F. distichus. CONCLUSIONS Different methodological approaches with variable set thresholds influence core identification, but a handful of core taxa are apparently identifiable as they are widespread and temporally associated with F. distichus and enriched in comparison to the environment. Moreover, we show that many of these core ASVs of F. distichus are found on multiple macroalgal hosts, indicating that most occupy a macroalgal generalist niche rather than forming highly specialized associations with F. distichus. Further studies should test whether macroalgal generalists or specialists are more likely to engage in biologically important exchanges with host.
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Affiliation(s)
- Jungsoo Park
- Department of Botany, Biodiversity Research Centre, University of British Columbia, Vancouver, BC Canada
| | - Katherine Davis
- Department of Botany, Biodiversity Research Centre, University of British Columbia, Vancouver, BC Canada
| | - Geneviève Lajoie
- Department of Botany, Biodiversity Research Centre, University of British Columbia, Vancouver, BC Canada
- Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, Montréal, QC Canada
| | - Laura Wegener Parfrey
- Department of Botany, Biodiversity Research Centre, University of British Columbia, Vancouver, BC Canada
- Department of Zoology, University of British Columbia, Vancouver, BC Canada
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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.
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Bongrand C, Koch E, Mende D, Romano A, Lawhorn S, McFall-Ngai M, DeLong EF, Ruby EG. Evidence of Genomic Diversification in a Natural Symbiotic Population Within Its Host. Front Microbiol 2022; 13:854355. [PMID: 35300477 PMCID: PMC8922018 DOI: 10.3389/fmicb.2022.854355] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 02/09/2022] [Indexed: 11/25/2022] Open
Abstract
Planktonic cells of the luminous marine bacterium Vibrio fischeri establish themselves in the light-emitting organ of each generation of newly hatched Euprymna scolopes bobtail squid. A symbiont population is maintained within the 6 separated crypts of the organ for the ∼9-month life of the host. In the wild, the initial colonization step is typically accomplished by a handful of planktonic V. fischeri cells, leading to a species-specific, but often multi-strain, symbiont population. Within a few hours, the inoculating cells proliferate within the organ’s individual crypts, after which there is evidently no supernumerary colonization. Nevertheless, every day at dawn, the majority of the symbionts is expelled, and the regrowth of the remaining ∼5% of cells provides a daily opportunity for the population to evolve and diverge, thereby increasing its genomic diversity. To begin to understand the extent of this diversification, we characterized the light-organ population of an adult animal. First, we used 16S sequencing to determine that species in the V. fischeri clade were essentially the only ones detectable within a field-caught E. scolopes. Efforts to colonize the host with a minor species that appeared to be identified, V. litoralis, revealed that, although some cells could be imaged within the organ, they were <0.1% of the typical V. fischeri population, and did not persist. Next, we determined the genome sequences of seventy-two isolates from one side of the organ. While all these isolates were associated with one of three clusters of V. fischeri strains, there was considerable genomic diversity within this natural symbiotic population. Comparative analyses revealed a significant difference in both the number and the presence/absence of genes within each cluster; in contrast, there was little accumulation of single-nucleotide polymorphisms. These data suggest that, in nature, the light organ is colonized by a small number of V. fischeri strains that can undergo significant genetic diversification, including by horizontal-gene transfer, over the course of ∼1500 generations of growth in the organ. When the resulting population of symbionts is expelled into seawater, its genomic mix provides the genetic basis for selection during the subsequent environmental dispersal, and transmission to the next host.
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Affiliation(s)
- Clotilde Bongrand
- Kewalo Marine Laboratory, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Eric Koch
- Kewalo Marine Laboratory, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Daniel Mende
- Department of Oceanography, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Anna Romano
- Department of Oceanography, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Susannah Lawhorn
- Kewalo Marine Laboratory, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Margaret McFall-Ngai
- Kewalo Marine Laboratory, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Edward F DeLong
- Department of Oceanography, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Edward G Ruby
- Kewalo Marine Laboratory, SOEST, University of Hawai'i at Mānoa, Honolulu, HI, United States
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9
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Allen C, Finkel SE. Vibrio harveyi Exhibits the Growth Advantage in Stationary Phase Phenotype during Long-Term Incubation. Microbiol Spectr 2022; 10:e0214421. [PMID: 35080444 PMCID: PMC8791185 DOI: 10.1128/spectrum.02144-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 12/26/2021] [Indexed: 11/20/2022] Open
Abstract
The bioluminescent marine bacterium Vibrio harveyi can exist within a host, acting as a mutualist or a parasitic microbe, and as planktonic cells in open seawater. This study demonstrates the ability of V. harveyi populations to survive and adapt under nutrient stress conditions in the laboratory, starting in an initially rich medium. V. harveyi populations remain viable into long-term stationary phase, for at least 1 month, without the addition of nutrients. To determine whether these communities are dynamic, populations were sampled after 10, 20, and 30 days of incubation and examined for their competitive ability when cocultured with an unaged, parental population. While populations incubated for 10 or 20 days showed some fitness advantage over parental populations, only after 30 days of incubation did all populations examined outcompete parental populations in coculture, fully expressing the growth advantage in stationary phase (GASP) phenotype. The ability to express GASP, in the absence of additional nutrients after inoculation, verifies the dynamism of long-term stationary-phase V. harveyi populations, implies the ability to generate genetic diversity, and demonstrates the plasticity of the V. harveyi genome, allowing for rapid adaptation for survival in changing culture environments. Despite the dynamism, the adaptation to the changing culture environment occurs less rapidly than in Escherichia coli, possibly due to Vibrio harveyi's lower mutation frequency. IMPORTANCE Vibrio harveyi populations exist in many different niches within the ocean environment, as free-living cells, symbionts with particular squid and fish species, and parasites to other marine organisms. It is important to understand V. harveyi's ability to survive and evolve within each of these niches. This study focuses on V. harveyi's lifestyle outside the host environment, demonstrating this microbe's ability to survive long-term culturing after inoculation in an initially rich medium and revealing increased competitive fitness correlated with incubation time when aged V. harveyi populations are cocultured with unaged, parental cultures. Thus, this study highlights the development of the growth advantage in stationary phase (GASP) phenotype in V. harveyi populations suggesting a dynamic population with fluctuating genotype frequencies throughout long-term, host-independent incubation.
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Affiliation(s)
- Calista Allen
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California, United States
| | - Steven E. Finkel
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California, United States
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10
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Nyholm SV, McFall-Ngai MJ. A lasting symbiosis: how the Hawaiian bobtail squid finds and keeps its bioluminescent bacterial partner. Nat Rev Microbiol 2021; 19:666-679. [PMID: 34089010 PMCID: PMC8440403 DOI: 10.1038/s41579-021-00567-y] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2021] [Indexed: 01/08/2023]
Abstract
For more than 30 years, the association between the Hawaiian bobtail squid, Euprymna scolopes, and the bioluminescent bacterium Vibrio fischeri has been studied as a model system for understanding the colonization of animal epithelia by symbiotic bacteria. The squid-vibrio light-organ system provides the exquisite resolution only possible with the study of a binary partnership. The impact of this relationship on the partners' biology has been broadly characterized, including their ecology and evolutionary biology as well as the underlying molecular mechanisms of symbiotic dynamics. Much has been learned about the factors that foster initial light-organ colonization, and more recently about the maturation and long-term maintenance of the association. This Review synthesizes the results of recent research on the light-organ association and also describes the development of new horizons for E. scolopes as a model organism that promises to inform biology and biomedicine about the basic nature of host-microorganism interactions.
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Affiliation(s)
- Spencer V Nyholm
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA.
| | - Margaret J McFall-Ngai
- Pacific Biosciences Research Center, Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, HI, USA.
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11
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Host-Like Conditions Are Required for T6SS-Mediated Competition among Vibrio fischeri Light Organ Symbionts. mSphere 2021; 6:e0128820. [PMID: 34287008 PMCID: PMC8386388 DOI: 10.1128/msphere.01288-20] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Bacteria employ diverse competitive strategies to enhance fitness and promote their own propagation. However, little is known about how symbiotic bacteria modulate competitive mechanisms as they compete for a host niche. The bacterium Vibrio fischeri forms a symbiotic relationship with marine animals and encodes a type VI secretion system (T6SS), which is a contact-dependent killing mechanism used to eliminate competitors during colonization of the Euprymna scolopes squid light organ. Like other horizontally acquired symbionts, V. fischeri experiences changes in its physical and chemical environment during symbiosis establishment. Therefore, we probed both environmental and host-like conditions to identify ecologically relevant cues that control T6SS-dependent competition during habitat transition. Although the T6SS did not confer a competitive advantage for V. fischeri strain ES401 under planktonic conditions, a combination of both host-like pH and viscosity was necessary for T6SS competition. For ES401, high viscosity activates T6SS expression and neutral/acidic pH promotes cell-cell contact for killing, and this pH-dependent phenotype was conserved in the majority of T6SS-encoding strains examined. We also identified a subset of V. fischeri isolates that engaged in T6SS-mediated competition at high viscosity under both planktonic and host-like pH conditions. T6SS phylogeny revealed that strains with pH-dependent phenotypes cluster together to form a subclade within the pH-independent strains, suggesting that V. fischeri may have recently evolved to limit competition to the host niche. IMPORTANCE Bacteria have evolved diverse strategies to compete for limited space and resources. Because these mechanisms can be costly to use, their expression and function are often restricted to specific environments where the benefits outweigh the costs. However, little is known about the specific cues that modulate competitive mechanisms as bacterial symbionts transition between free-living and host habitats. Here, we used the bioluminescent squid and fish symbiont Vibrio fischeri to probe for host and environmental conditions that control interbacterial competition via the type VI secretion system. Our findings identify a new host-specific cue that promotes competition among many but not all V. fischeri isolates, underscoring the utility of studying multiple strains to reveal how competitive mechanisms may be differentially regulated among closely related populations as they evolve to fill distinct niches.
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12
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Dial CN, Eichinger SJ, Foxall R, Corcoran CJ, Tischler AH, Bolz RM, Whistler CA, Visick KL. Quorum Sensing and Cyclic di-GMP Exert Control Over Motility of Vibrio fischeri KB2B1. Front Microbiol 2021; 12:690459. [PMID: 34262549 PMCID: PMC8273514 DOI: 10.3389/fmicb.2021.690459] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 05/28/2021] [Indexed: 11/23/2022] Open
Abstract
Bacterial motility is critical for symbiotic colonization by Vibrio fischeri of its host, the squid Euprymna scolopes, facilitating movement from surface biofilms to spaces deep inside the symbiotic organ. While colonization has been studied traditionally using strain ES114, others, including KB2B1, can outcompete ES114 for colonization for a variety of reasons, including superior biofilm formation. We report here that KB2B1 also exhibits an unusual pattern of migration through a soft agar medium: whereas ES114 migrates rapidly and steadily, KB2B1 migrates slowly and then ceases migration. To better understand this phenomenon, we isolated and sequenced five motile KB2B1 suppressor mutants. One harbored a mutation in the gene for the cAMP receptor protein (crp); because this strain also exhibited a growth defect, it was not characterized further. Two other suppressors contained mutations in the quorum sensing pathway that controls bacterial bioluminescence in response to cell density, and two had mutations in the diguanylate cyclase (DGC) gene VF_1200. Subsequent analysis indicated that (1) the quorum sensing mutations shifted KB2B1 to a perceived low cell density state and (2) the high cell density state inhibited migration via the downstream regulator LitR. Similar to the initial point mutations, deletion of the VF_1200 DGC gene increased migration. Consistent with the possibility that production of the second messenger c-di-GMP inhibited the motility of KB2B1, reporter-based measurements of c-di-GMP revealed that KB2B1 produced higher levels of c-di-GMP than ES114, and overproduction of a c-di-GMP phosphodiesterase promoted migration of KB2B1. Finally, we assessed the role of viscosity in controlling the quorum sensing pathway using polyvinylpyrrolidone and found that viscosity increased light production of KB2B1 but not ES114. Together, our data indicate that while the two strains share regulators in common, they differ in the specifics of the regulatory control over downstream phenotypes such as motility.
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Affiliation(s)
- Courtney N. Dial
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, United States
| | - Steven J. Eichinger
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, United States
| | - Randi Foxall
- Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH, United States
| | - Christopher J. Corcoran
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, United States
| | - Alice H. Tischler
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, United States
| | - Robert M. Bolz
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, United States
| | - Cheryl A. Whistler
- Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH, United States
| | - Karen L. Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, United States
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13
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A lasting symbiosis: how Vibrio fischeri finds a squid partner and persists within its natural host. Nat Rev Microbiol 2021; 19:654-665. [PMID: 34089008 DOI: 10.1038/s41579-021-00557-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2021] [Indexed: 01/10/2023]
Abstract
As our understanding of the human microbiome progresses, so does the need for natural experimental animal models that promote a mechanistic understanding of beneficial microorganism-host interactions. Years of research into the exclusive symbiosis between the Hawaiian bobtail squid, Euprymna scolopes, and the bioluminescent bacterium Vibrio fischeri have permitted a detailed understanding of those bacterial genes underlying signal exchange and rhythmic activities that result in a persistent, beneficial association, as well as glimpses into the evolution of symbiotic competence. Migrating from the ambient seawater to regions deep inside the light-emitting organ of the squid, V. fischeri experiences, recognizes and adjusts to the changing environmental conditions. Here, we review key advances over the past 15 years that are deepening our understanding of these events.
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14
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Christensen DG, Visick KL. Vibrio fischeri: Laboratory Cultivation, Storage, and Common Phenotypic Assays. ACTA ACUST UNITED AC 2021; 57:e103. [PMID: 32497392 DOI: 10.1002/cpmc.103] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Vibrio fischeri is a nonpathogenic organism related to pathogenic Vibrio species that can be readily grown and stored with common laboratory equipment. In this article, protocols for routine growth, storage, and phenotypic assessment of V. fischeri, as well as recipes for useful media, are included. Specifically, this article describes procedures and considerations for growth of this microbe in complex and minimal media. It also describes assays for biofilm formation, motility, and bioluminescence, three commonly assessed phenotypes of V. fischeri. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Growth of V. fischeri from frozen stocks Basic Protocol 2: Growth of V. fischeri in rich, undefined liquid medium Alternate Protocol 1: Growth of V. fischeri in minimal medium Basic Protocol 3: Storage of V. fischeri in frozen stocks Basic Protocol 4: Biofilm assay on solid agar Alternate Protocol 2: Biofilm assay in shaking liquid culture Alternate Protocol 3: Biofilm assay in static liquid culture Basic Protocol 5: Motility assay Basic Protocol 6: Luminescence assay.
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Affiliation(s)
- David G Christensen
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois
| | - Karen L Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois
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15
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Goodrich-Blair H. Interactions of host-associated multispecies bacterial communities. Periodontol 2000 2021; 86:14-31. [PMID: 33690897 DOI: 10.1111/prd.12360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The oral microbiome comprises microbial communities colonizing biotic (epithelia, mucosa) and abiotic (enamel) surfaces. Different communities are associated with health (eg, immune development, pathogen resistance) and disease (eg, tooth loss and periodontal disease). Like any other host-associated microbiome, colonization and persistence of both beneficial and dysbiotic oral microbiomes are dictated by successful utilization of available nutrients and defense against host and competitor assaults. This chapter will explore these general features of microbe-host interactions through the lens of symbiotic (mutualistic and antagonistic/pathogenic) associations with nonmammalian animals. Investigations in such systems across a broad taxonomic range have revealed conserved mechanisms and processes that underlie the complex associations among microbes and between microbes and hosts.
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Affiliation(s)
- Heidi Goodrich-Blair
- Department of Microbiology, University of Tennessee-Knoxville, Knoxville, Tennessee, USA
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16
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Control of Competence in Vibrio fischeri. Appl Environ Microbiol 2021; 87:AEM.01962-20. [PMID: 33397700 DOI: 10.1128/aem.01962-20] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 12/22/2020] [Indexed: 01/18/2023] Open
Abstract
Vibrio species, including the squid symbiont Vibrio fischeri, become competent to take up DNA under specific conditions. For example, V. fischeri becomes competent when grown in the presence of chitin oligosaccharides or upon overproduction of the competence regulatory factor TfoX. While little is known about the regulatory pathway(s) that controls V. fischeri competence, this microbe encodes homologs of factors that control competence in the well-studied V. cholerae To further develop V. fischeri as a genetically tractable organism, we evaluated the roles of some of these competence homologs. Using TfoX-overproducing cells, we found that competence depends upon LitR, the homolog of V. cholerae master quorum-sensing and competence regulator HapR, and upon homologs of putative pilus genes that in V. cholerae facilitate DNA uptake. Disruption of genes for negative regulators upstream of LitR, namely, the LuxO protein and the small RNA (sRNA) Qrr1, resulted in increased transformation frequencies. Unlike LitR-controlled light production, however, competence did not vary with cell density under tfoX overexpression conditions. Analogous to the case with V. cholerae, the requirement for LitR could be suppressed by loss of the Dns nuclease. We also found a role for the putative competence regulator CytR. Finally, we determined that transformation frequencies varied depending on the TfoX-encoding plasmid, and we developed a new dual tfoX and litR overexpression construct that substantially increased the transformation frequency of a less genetically tractable strain. By advancing the ease of genetic manipulation of V. fischeri, these findings will facilitate the rapid discovery of genes involved in physiologically relevant processes, such as biofilm formation and host colonization.IMPORTANCE The ability of bacteria to take up DNA (competence) and incorporate foreign DNA into their genomes (transformation) permits them to rapidly evolve and gain new traits and/or acquire antibiotic resistances. It also facilitates laboratory-based investigations into mechanisms of specific phenotypes, such as those involved in host colonization. Vibrio fischeri has long been a model for symbiotic bacterium-host interactions as well as for other aspects of its physiology, such as bioluminescence and biofilm formation. Competence of V. fischeri can be readily induced upon overexpression of the competence factor TfoX. Relatively little is known about the V. fischeri competence pathway, although homologs of factors known to be important in V. cholerae competence exist. By probing the importance of putative competence factors that control transformation of V. fischeri, this work deepens our understanding of the competence process and advances our ability to genetically manipulate this important model organism.
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17
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Klemetsen T, Karlsen CR, Willassen NP. Phylogenetic Revision of the Genus Aliivibrio: Intra- and Inter-Species Variance Among Clusters Suggest a Wider Diversity of Species. Front Microbiol 2021; 12:626759. [PMID: 33679646 PMCID: PMC7930494 DOI: 10.3389/fmicb.2021.626759] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 01/27/2021] [Indexed: 12/15/2022] Open
Abstract
Genus Aliivibrio is known to harbor species exhibiting bioluminescence as well as pathogenic behavior affecting the fish farming industry. Current phylogenetic understanding of Aliivibrio has largely remained dormant after reclassification disentangled it from the Vibrio genus in 2007. There is growing evidence of wider diversity, but until now the lack of genomes and selective use of type strains have limited the ability to compare and classify strains firmly. In this study, a total of 143 bacterial strains, including 51 novel sequenced strains, were used to strengthen phylogenetic relationships in Aliivibrio by exploring intra-species and inter-species relations. Multilocus sequence analysis (MLSA), applying the six housekeeping genes 16S ribosomal RNA (rRNA), gapA, gyrB, pyrH, recA, and rpoA, inferred 12 clades and a singular branch in Aliivibrio. Along with four new phylogenetic clades, the MLSA resolved prior inconsistencies circumscribing Aliivibrio wodanis and formed a unique clade we propose as the novel species Aliivibrio sp. “friggae.” Furthermore, phylogenetic assessment of individual marker genes showed gyrB, pyrH, and recA superior to the 16S rRNA gene, resolving accurately for most species clades in Aliivibrio. In this study, we provide a robust phylogenetic groundwork for Aliivibrio as a reference point to classification of species.
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Affiliation(s)
- Terje Klemetsen
- Department of Chemistry, Center for Bioinformatics, UiT The Arctic University of Norway, Tromsø, Norway
| | | | - Nils P Willassen
- Department of Chemistry, Center for Bioinformatics, UiT The Arctic University of Norway, Tromsø, Norway
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18
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Ruby E. Getting to know our microbial friends by dropping into their neighbourhood. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:27-30. [PMID: 33047473 DOI: 10.1111/1758-2229.12895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 10/08/2020] [Indexed: 06/11/2023]
Affiliation(s)
- Edward Ruby
- Kewalo Marine Laboratory, Pacific Biosciences Research Center, University of Hawaii at Manoa, Honolulu, HI, 96813, USA
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19
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Gould AL, Fritts-Penniman A, Gaisiner A. Museum Genomics Illuminate the High Specificity of a Bioluminescent Symbiosis for a Genus of Reef Fish. Front Ecol Evol 2021; 9:630207. [PMID: 34485316 PMCID: PMC8412414 DOI: 10.3389/fevo.2021.630207] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Symbiotic relationships between bioluminescent bacteria and fishes have evolved multiple times across hundreds of fish taxa, but relatively little is known about the specificity of these associations and how stable they are over host generations. This study describes the degree of specificity of a bioluminescent symbiosis between cardinalfishes in the genus Siphamia and luminous bacteria in the Vibrio family. Primarily using museum specimens, we investigated the codivergence of host and symbiont and test for patterns of divergence that correlate with both biogeography and time. Contrary to expectations, we determined that the light organ symbionts of all 14 Siphamia species examined belong to one genetic clade of Photobacterium mandapamensis (Clade II), indicating that the association is highly specific and conserved throughout the host genus. Thus, we did not find evidence of codivergence among hosts and symbionts. We did observe that symbionts hosted by individuals sampled from colder water regions were more divergent, containing more than three times as many single nucleotide polymorphisms than the rest of the symbionts examined. Overall, our findings indicate that the symbiosis between Siphamia fishes and P. mandapamensis Clade II has been highly conserved across host taxa and over a broad geographic range despite the facultative nature of the bacterial symbiont. We also present a new approach to simultaneously recover genetic information from a bacterial symbiont and its vertebrate host from formalin-fixed specimens, enhancing the utility of museum collections.
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Affiliation(s)
- Alison L. Gould
- California Academy of Sciences, San Francisco, CA, United States
| | | | - Ana Gaisiner
- California Academy of Sciences, San Francisco, CA, United States
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20
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McFall-Ngai M, Bosch TCG. Animal development in the microbial world: The power of experimental model systems. Curr Top Dev Biol 2020; 141:371-397. [PMID: 33602493 PMCID: PMC8211120 DOI: 10.1016/bs.ctdb.2020.10.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The development of powerful model systems has been a critical strategy for understanding the mechanisms underlying the progression of an animal through its ontogeny. Here we provide two examples that allow deep and mechanistic insight into the development of specific animal systems. Species of the cnidarian genus Hydra have provided excellent models for studying host-microbe interactions and how metaorganisms function in vivo. Studies of the Hawaiian bobtail squid Euprymna scolopes and its luminous bacterial partner Vibrio fischeri have been used for over 30 years to understand the impact of a broad array of levels, from ecology to genomics, on the development and persistence of symbiosis. These examples provide an integrated perspective of how developmental processes work and evolve within the context of a microbial world, a new view that opens vast horizons for developmental biology research. The Hydra and the squid systems also lend an example of how profound insights can be discovered by taking advantage of the "experiments" that evolution had done in shaping conserved developmental processes.
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Affiliation(s)
- Margaret McFall-Ngai
- Pacific Biosciences Research Center, Kewalo Marine Laboratory, University of Hawai'i at Mānoa, Honolulu, HI, United States.
| | - Thomas C G Bosch
- Zoological Institute, Christian-Albrechts-University Kiel, Kiel, Germany
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21
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Christensen DG, Marsden AE, Hodge-Hanson K, Essock-Burns T, Visick KL. LapG mediates biofilm dispersal in Vibrio fischeri by controlling maintenance of the VCBS-containing adhesin LapV. Mol Microbiol 2020; 114:742-761. [PMID: 32654271 DOI: 10.1111/mmi.14573] [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: 04/29/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 12/18/2022]
Abstract
Efficient symbiotic colonization of the squid Euprymna scolopes by the bacterium Vibrio fischeri depends on bacterial biofilm formation on the surface of the squid's light organ. Subsequently, the bacteria disperse from the biofilm via an unknown mechanism and enter through pores to reach the interior colonization sites. Here, we identify a homolog of Pseudomonas fluorescens LapG as a dispersal factor that promotes cleavage of a biofilm-promoting adhesin, LapV. Overproduction of LapG inhibited biofilm formation and, unlike the wild-type parent, a ΔlapG mutant formed biofilms in vitro. Although V. fischeri encodes two putative large adhesins, LapI (near lapG on chromosome II) and LapV (on chromosome I), only the latter contributed to biofilm formation. Consistent with the Pseudomonas Lap system model, our data support a role for the predicted c-di-GMP-binding protein LapD in inhibiting LapG-dependent dispersal. Furthermore, we identified a phosphodiesterase, PdeV, whose loss promotes biofilm formation similar to that of the ΔlapG mutant and dependent on both LapD and LapV. Finally, we found a minor defect for a ΔlapD mutant in initiating squid colonization, indicating a role for the Lap system in a relevant environmental niche. Together, these data reveal new factors and provide important insights into biofilm dispersal by V. fischeri.
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Affiliation(s)
- David G Christensen
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, USA
| | - Anne E Marsden
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, USA
| | - Kelsey Hodge-Hanson
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, USA
| | - Tara Essock-Burns
- Kewalo Marine Laboratory, Pacific Biosciences Research Center, University of Hawai'i at Mānoa, Honolulu, HI, USA
| | - Karen L Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, IL, USA
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22
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Interactions of Symbiotic Partners Drive the Development of a Complex Biogeography in the Squid-Vibrio Symbiosis. mBio 2020; 11:mBio.00853-20. [PMID: 32457244 PMCID: PMC7251207 DOI: 10.1128/mbio.00853-20] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The complexity, inaccessibility, and time scales of initial colonization of most animal microbiomes present challenges for the characterization of how the bacterial symbionts influence the form and function of tissues in the minutes to hours following the initial interaction of the partners. Here, we use the naturally occurring binary squid-vibrio association to explore this phenomenon. Imaging of the spatiotemporal landscape of this symbiosis during its onset provides a window into the impact of differences in both host-tissue maturation and symbiont strain phenotypes on the establishment of a dynamically stable symbiotic system. These data provide evidence that the symbionts shape the host-tissue landscape and that tissue maturation impacts the influence of strain-level differences on the daily rhythms of the symbiosis, the competitiveness for colonization, and antibiotic sensitivity. Microbes live in complex microniches within host tissues, but how symbiotic partners communicate to create such niches during development remains largely unexplored. Using confocal microscopy and symbiont genetics, we characterized the shaping of host microenvironments during light organ colonization of the squid Euprymna scolopes by the bacterium Vibrio fischeri. During embryogenesis, three pairs of invaginations form sequentially on the organ’s surface, producing pores that lead to interior compressed tubules at different stages of development. After hatching, these areas expand, allowing V. fischeri cells to enter and migrate ∼120 μm through three anatomically distinct regions before reaching blind-ended crypt spaces. A dynamic gatekeeper, or bottleneck, connects these crypts with the migration path. Once V. fischeri cells have entered the crypts, the bottlenecks narrow, and colonization by the symbiont population becomes spatially restricted. The actual timing of constriction and restriction varies with crypt maturity and with different V. fischeri strains. Subsequently, starting with the first dawn following colonization, the bottleneck controls a lifelong cycle of dawn-triggered expulsions of most of the symbionts into the environment and a subsequent regrowth in the crypts. Unlike other developmental phenotypes, bottleneck constriction is not induced by known microbe-associated molecular patterns (MAMPs) or by V. fischeri-produced bioluminescence, but it does require metabolically active symbionts. Further, while symbionts in the most mature crypts have a higher proportion of live cells and a greater likelihood of expulsion at dawn, they have a lower resistance to antibiotics. The overall dynamics of these distinct microenvironments reflect the complexity of the host-symbiont dialogue.
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Bongrand C, Moriano-Gutierrez S, Arevalo P, McFall-Ngai M, Visick KL, Polz M, Ruby EG. Using Colonization Assays and Comparative Genomics To Discover Symbiosis Behaviors and Factors in Vibrio fischeri. mBio 2020; 11:e03407-19. [PMID: 32127462 PMCID: PMC7064787 DOI: 10.1128/mbio.03407-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 01/21/2020] [Indexed: 12/14/2022] Open
Abstract
The luminous marine Gram-negative bacterium Vibrio (Aliivibrio) fischeri is the natural light organ symbiont of several squid species, including the Hawaiian bobtail squid, Euprymna scolopes, and the Japanese bobtail squid, Euprymna morsei Work with E. scolopes has shown how the bacteria establish their niche in the light organ of the newly hatched host. Two types of V. fischeri strains have been distinguished based upon their behavior in cocolonization competition assays in juvenile E. scolopes, i.e., (i) niche-sharing or (ii) niche-dominant behavior. This study aimed to determine whether these behaviors are observed with other V. fischeri strains or whether they are specific to those isolated from E. scolopes light organs. Cocolonization competition assays between V. fischeri strains isolated from the congeneric squid E. morsei or from other marine animals revealed the same sharing or dominant behaviors. In addition, whole-genome sequencing of these strains showed that the dominant behavior is polyphyletic and not associated with the presence or absence of a single gene or genes. Comparative genomics of 44 squid light organ isolates from around the globe led to the identification of symbiosis-specific candidates in the genomes of these strains. Colonization assays using genetic derivatives with deletions of these candidates established the importance of two such genes in colonization. This study has allowed us to expand the concept of distinct colonization behaviors to strains isolated from a number of squid and fish hosts.IMPORTANCE There is an increasing recognition of the importance of strain differences in the ecology of a symbiotic bacterial species and, in particular, how these differences underlie crucial interactions with their host. Nevertheless, little is known about the genetic bases for these differences, how they manifest themselves in specific behaviors, and their distribution among symbionts of different host species. In this study, we sequenced the genomes of Vibrio fischeri isolated from the tissues of squids and fishes and applied comparative genomics approaches to look for patterns between symbiont lineages and host colonization behavior. In addition, we identified the only two genes that were exclusively present in all V. fischeri strains isolated from the light organs of sepiolid squid species. Mutational studies of these genes indicated that they both played a role in colonization of the squid light organ, emphasizing the value of applying a comparative genomics approach in the study of symbioses.
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Affiliation(s)
| | | | - Philip Arevalo
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | | | - Karen L Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
| | - Martin Polz
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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Apprill A. The Role of Symbioses in the Adaptation and Stress Responses of Marine Organisms. ANNUAL REVIEW OF MARINE SCIENCE 2020; 12:291-314. [PMID: 31283425 DOI: 10.1146/annurev-marine-010419-010641] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Ocean ecosystems are experiencing unprecedented rates of climate and anthropogenic change, which can often initiate stress in marine organisms. Symbioses, or associations between different organisms, are plentiful in the ocean and could play a significant role in facilitating organismal adaptations to stressful ocean conditions. This article reviews current knowledge about the role of symbiosis in marine organismal acclimation and adaptation. It discusses stress and adaptations in symbioses from coral reef ecosystems, which are among the most affected environments in the ocean, including the relationships between corals and microalgae, corals and bacteria, anemones and clownfish, and cleaner fish and client fish. Despite the importance of this subject, knowledge of how marine organisms adapt to stress is still limited, and there are vast opportunities for research and technological development in this area. Attention to this subject will enhance our understanding of the capacity of symbioses to alleviate organismal stress in the oceans.
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Affiliation(s)
- Amy Apprill
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA;
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Aschtgen MS, Brennan CA, Nikolakakis K, Cohen S, McFall-Ngai M, Ruby EG. Insights into flagellar function and mechanism from the squid-vibrio symbiosis. NPJ Biofilms Microbiomes 2019; 5:32. [PMID: 31666982 PMCID: PMC6814793 DOI: 10.1038/s41522-019-0106-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 10/03/2019] [Indexed: 02/07/2023] Open
Abstract
Flagella are essential and multifunctional nanomachines that not only move symbionts towards their tissue colonization site, but also play multiple roles in communicating with the host. Thus, untangling the activities of flagella in reaching, interacting, and signaling the host, as well as in biofilm formation and the establishment of a persistent colonization, is a complex problem. The squid-vibrio system offers a unique model to study the many ways that bacterial flagella can influence a beneficial association and, generally, other bacteria-host interactions. Vibrio fischeri is a bioluminescent bacterium that colonizes the Hawaiian bobtail squid, Euprymna scolopes. Over the last 15 years, the structure, assembly, and functions of V. fischeri flagella, including not only motility and chemotaxis, but also biofilm formation and symbiotic signaling, have been revealed. Here we discuss these discoveries in the perspective of other host-bacteria interactions.
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Affiliation(s)
- Marie-Stephanie Aschtgen
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706 USA
- Present Address: Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Solna, 171 76 Sweden
| | - Caitlin A. Brennan
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706 USA
- Present Address: Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA 02115 USA
| | - Kiel Nikolakakis
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706 USA
- Present Address: Department of Natural and Applied Sciences, University of Wisconsin – Green Bay, Green Bay, WI 54311 USA
| | - Stephanie Cohen
- Laboratory for Biological Geochemistry, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, and Center for Advanced Surface Analysis, Institute of Earth Sciences, Université de Lausanne, CH-1015 Lausanne, Switzerland
- Kewalo Marine Laboratory, University of Hawaii-Manoa, Honolulu, HI 96813 USA
| | | | - Edward G. Ruby
- Kewalo Marine Laboratory, University of Hawaii-Manoa, Honolulu, HI 96813 USA
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Ansorge R, Romano S, Sayavedra L, Porras MÁG, Kupczok A, Tegetmeyer HE, Dubilier N, Petersen J. Functional diversity enables multiple symbiont strains to coexist in deep-sea mussels. Nat Microbiol 2019; 4:2487-2497. [DOI: 10.1038/s41564-019-0572-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 08/28/2019] [Indexed: 12/13/2022]
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Bongrand C, Ruby EG. The impact of Vibrio fischeri strain variation on host colonization. Curr Opin Microbiol 2019; 50:15-19. [PMID: 31593868 DOI: 10.1016/j.mib.2019.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 08/17/2019] [Accepted: 09/02/2019] [Indexed: 01/06/2023]
Abstract
Strain-level epidemiology is a key approach to understanding the mechanisms underlying establishment of any host-microbe association. The squid-vibrio light organ symbiosis has proven to be an informative and tractable experimental model in which to discover these mechanisms because it involves only one bacterial species, Vibrio fischeri. In this horizontally transmitted symbiosis, the squid presents nutrients to the bacteria located in a bilobed light-emitting organ, while the symbionts provide bioluminescence to their host. To initiate this association, V. fischeri cells go through several distinct stages: from free-living in the bacterioplankton, to forming a multicellular aggregation near pores on the light organ's surface, to migrating through the pores and into crypts deep in the light organ, where the symbiont population grows and luminesces. Because individual cells must successfully navigate these distinct regions, phenotypic differences between strains will have a strong impact on the composition of the population finally colonizing the squid. Here we review recent advances in our understanding of behavioral characteristics that differentially drive a strain's success, including its effectiveness of aggregation, the rapidity with which it reaches the deep crypts, and its deployment of type VI secretion.
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Wein T, Romero Picazo D, Blow F, Woehle C, Jami E, Reusch TB, Martin WF, Dagan T. Currency, Exchange, and Inheritance in the Evolution of Symbiosis. Trends Microbiol 2019; 27:836-849. [DOI: 10.1016/j.tim.2019.05.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 05/19/2019] [Accepted: 05/30/2019] [Indexed: 12/28/2022]
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Baker LJ, Freed LL, Easson CG, Lopez JV, Fenolio D, Sutton TT, Nyholm SV, Hendry TA. Diverse deep-sea anglerfishes share a genetically reduced luminous symbiont that is acquired from the environment. eLife 2019; 8:47606. [PMID: 31571583 PMCID: PMC6773444 DOI: 10.7554/elife.47606] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Accepted: 08/21/2019] [Indexed: 11/13/2022] Open
Abstract
Deep-sea anglerfishes are relatively abundant and diverse, but their luminescent bacterial symbionts remain enigmatic. The genomes of two symbiont species have qualities common to vertically transmitted, host-dependent bacteria. However, a number of traits suggest that these symbionts may be environmentally acquired. To determine how anglerfish symbionts are transmitted, we analyzed bacteria-host codivergence across six diverse anglerfish genera. Most of the anglerfish species surveyed shared a common species of symbiont. Only one other symbiont species was found, which had a specific relationship with one anglerfish species, Cryptopsaras couesii. Host and symbiont phylogenies lacked congruence, and there was no statistical support for codivergence broadly. We also recovered symbiont-specific gene sequences from water collected near hosts, suggesting environmental persistence of symbionts. Based on these results we conclude that diverse anglerfishes share symbionts that are acquired from the environment, and that these bacteria have undergone extreme genome reduction although they are not vertically transmitted. The deep sea is home to many different species of anglerfish, a group of animals in which females often display a dangling lure on the top of their heads. This organ shelters bacteria that make light, a partnership (known as symbiosis) that benefits both parties. The bacteria get a safe environment in which to grow, while the animal may use the light to confuse predators as well as attract prey and mates. The genetic information of these bacteria has changed since they became associated with their host. Their genomes have become smaller and more specialized, limiting their ability to survive outside of the fish. This phenomenon is also observed in other symbiotic bacteria, but mostly in microorganisms that are directly transmitted from parent to offspring, never having to live on their own. Yet, some evidence suggests that the bacteria in the lure of anglerfish may be spending time in the water until they find a new host, crossing thousands of meters of ocean in the process. To explore this paradox, Baker et al. looked into the type of bacteria carried by different groups of anglerfish. If each type of fish has its own kind of bacteria, this would suggest that the microorganisms are passed from one generation to the next, and are evolving with their hosts. On the other hand, if the same sort of bacteria can be found in different anglerfish species, this would imply that the bacteria pass from host to host and evolve independently from the fish. Genetic data analysis showed that amongst six groups of anglerfishes, one species of bacteria is shared across five groups while another is specific to one type of fish. The analyses also revealed that anglerfish and their bacteria are most likely not evolving together. This means that the bacteria must make the difficult journey from host to host by persisting in the deep sea, which was confirmed by finding the genetic information of these bacteria in the water near the fish. Anglerfish and the bacteria that light up their lure are hard to study, as they live so deep in the ocean. In fact, many symbiotic relationships are equally difficult to investigate. Examining genetic information can help to give an insight into how hosts and bacteria interact across the tree of life.
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Affiliation(s)
- Lydia J Baker
- Department of Microbiology, Cornell University, New York, United States
| | - Lindsay L Freed
- Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, Fort Lauderdale, United States
| | - Cole G Easson
- Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, Fort Lauderdale, United States.,Department of Biology, Middle Tennessee State University, Murfreesboro, United States
| | - Jose V Lopez
- Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, Fort Lauderdale, United States
| | - Danté Fenolio
- Center for Conservation and Research, San Antonio Zoo, San Antonio, United States
| | - Tracey T Sutton
- Halmos College of Natural Sciences and Oceanography, Nova Southeastern University, Fort Lauderdale, United States
| | - Spencer V Nyholm
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, United States
| | - Tory A Hendry
- Department of Microbiology, Cornell University, New York, United States
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Natural Strain Variation Reveals Diverse Biofilm Regulation in Squid-Colonizing Vibrio fischeri. J Bacteriol 2019; 201:JB.00033-19. [PMID: 30782630 DOI: 10.1128/jb.00033-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 02/07/2019] [Indexed: 12/17/2022] Open
Abstract
The mutualistic symbiont Vibrio fischeri builds a symbiotic biofilm during colonization of squid hosts. Regulation of the exopolysaccharide component, termed Syp, has been examined in strain ES114, where production is controlled by a phosphorelay that includes the inner membrane hybrid histidine kinase RscS. Most strains that lack RscS or encode divergent RscS proteins cannot colonize a squid host unless RscS from a squid symbiont is heterologously expressed. In this study, we examine V. fischeri isolates worldwide to understand the landscape of biofilm regulation during beneficial colonization. We provide a detailed study of three distinct evolutionary groups of V. fischeri and find that while the RscS-Syp biofilm pathway is required in one of the groups, two other groups of squid symbionts require Syp independent of RscS. Mediterranean squid symbionts, including V. fischeri SR5, colonize without an RscS homolog encoded by their genome. Additionally, group A V. fischeri strains, which form a tightly related clade of Hawaii isolates, have a frameshift in rscS and do not require the gene for squid colonization or competitive fitness. These same strains have a frameshift in sypE, and we provide evidence that this group A sypE allele leads to an upregulation in biofilm activity. Thus, this work describes the central importance of Syp biofilm in colonization of diverse isolates and demonstrates that significant evolutionary transitions correspond to regulatory changes in the syp pathway.IMPORTANCE Biofilms are surface-associated, matrix-encased bacterial aggregates that exhibit enhanced protection to antimicrobial agents. Previous work has established the importance of biofilm formation by a strain of luminous Vibrio fischeri bacteria as the bacteria colonize their host, the Hawaiian bobtail squid. In this study, expansion of this work to many natural isolates revealed that biofilm genes are universally required, yet there has been a shuffling of the regulators of those genes. This work provides evidence that even when bacterial behaviors are conserved, dynamic regulation of those behaviors can underlie evolution of the host colonization phenotype. Furthermore, this work emphasizes the importance of investigating natural diversity as we seek to understand molecular mechanisms in bacteria.
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Girard L, Blanchet E, Stien D, Baudart J, Suzuki M, Lami R. Evidence of a Large Diversity of N-acyl-Homoserine Lactones in Symbiotic Vibrio fischeri Strains Associated with the Squid Euprymna scolopes. Microbes Environ 2019; 34:99-103. [PMID: 30760664 PMCID: PMC6440727 DOI: 10.1264/jsme2.me18145] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Vibrio fischeri possesses a complex AHL-mediated Quorum-sensing (QS) system including two pathways, LuxI/R (3-oxo-C6-HSL and C6-HSL) and AinS/R (C8-HSL), which are important for the regulation of physiological traits. Diverse QS-dependent functional phenotypes have been described in V. fischeri; however, AHL diversity is still underestimated. In the present study, we investigated AHL diversity in five symbiotic V. fischeri strains with distinct phenotypic properties using UHPLC-HRMS/MS. The results obtained (1) revealed an unexpectedly high diversity of signaling molecules, (2) emphasized the complexity of QS in V. fischeri, and (3) highlight the importance of understanding the specificity of AHL-mediated QS.
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Affiliation(s)
- Léa Girard
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique
| | - Elodie Blanchet
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique
| | - Didier Stien
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique
| | - Julia Baudart
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique
| | - Marcelino Suzuki
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique
| | - Raphaël Lami
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biodiversité et Biotechnologies Microbiennes (LBBM), Observatoire Océanologique
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Achieving a multi-strain symbiosis: strain behavior and infection dynamics. ISME JOURNAL 2018; 13:698-706. [PMID: 30353039 DOI: 10.1038/s41396-018-0305-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Revised: 09/16/2018] [Accepted: 10/09/2018] [Indexed: 01/30/2023]
Abstract
Strain diversity, while now recognized as a key driver underlying partner dynamics in symbioses, is usually difficult to experimentally manipulate and image in hosts with complex microbiota. To address this problem, we have used the luminous marine bacterium Vibrio fischeri, which establishes a symbiosis within the crypts of the nascent light organ of the squid Euprymna scolopes. Competition assays in newly hatched juvenile squid have shown that symbiotic V. fischeri are either niche-sharing "S strains", which share the light organ when co-inoculated with other S strains, or niche-dominant "D strains", which are typically found alone in the light organ after a co-colonization. To understand this D strain advantage, we determined the minimum time that different V. fischeri strains needed to initiate colonization and used confocal microscopy to localize the symbionts along their infection track. Further, we determined whether symbiont-induced host morphogenic events also occurred earlier during a D strain colonization. We conclude that D strains colonized more quickly than S strains. Nevertheless, light-organ populations in field-caught adult squid often contain both D and S strains. We determined experimentally that this symbiont population heterogeneity might be achieved in nature by a serial encounter of different strains in the environment.
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Koehler S, Gaedeke R, Thompson C, Bongrand C, Visick K, Ruby E, McFall-Ngai M. The model squid-vibrio symbiosis provides a window into the impact of strain- and species-level differences during the initial stages of symbiont engagement. Environ Microbiol 2018; 21:10.1111/1462-2920.14392. [PMID: 30136358 PMCID: PMC6386636 DOI: 10.1111/1462-2920.14392] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 08/14/2018] [Accepted: 08/18/2018] [Indexed: 11/29/2022]
Abstract
Among horizontally acquired symbioses, the mechanisms underlying microbial strain- and species-level specificity remain poorly understood. Here, confocal-microscopy analyses and genetic manipulation of the squid-vibrio association revealed quantitative differences in a symbiont's capacity to interact with the host during initial engagement. Specifically, dominant strains of Vibrio fischeri, 'D-type', previously named for their dominant, single-strain colonization of the squid's bioluminescent organ, were compared with 'S-type', or 'sharing', strains, which can co-colonize the organ. These D-type strains typically: (i) formed aggregations of 100s-1000s of cells on the light-organ surface, up to 3 orders of magnitude larger than those of S-type strains; (ii) showed dominance in co-aggregation experiments, independent of inoculum size or strain proportion; (iii) perturbed larger areas of the organ's ciliated surface; and, (iv) appeared at the pore of the organ approximately 4×s more quickly than S-type strains. At least in part, genes responsible for biofilm synthesis control the hyperaggregation phenotype of a D-type strain. Other marine vibrios produced relatively small aggregations, while an array of marine Gram-positive and -negative species outside of the Vibrionaceae did not attach to the organ's surface. These studies provide insight into the impact of strain variation on early events leading to establishment of an environmentally acquired symbiosis.
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Affiliation(s)
- Sabrina Koehler
- Pacific Biosciences Research Center, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Roxane Gaedeke
- Pacific Biosciences Research Center, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Cecilia Thompson
- Department of Microbiology and Immunology, Loyola University Chicago, IL, USA
| | - Clotilde Bongrand
- Pacific Biosciences Research Center, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Karen Visick
- Department of Microbiology and Immunology, Loyola University Chicago, IL, USA
| | - Edward Ruby
- Pacific Biosciences Research Center, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Margaret McFall-Ngai
- Pacific Biosciences Research Center, University of Hawaii at Manoa, Honolulu, HI, USA
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Bacterial symbionts use a type VI secretion system to eliminate competitors in their natural host. Proc Natl Acad Sci U S A 2018; 115:E8528-E8537. [PMID: 30127013 PMCID: PMC6130350 DOI: 10.1073/pnas.1808302115] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Competition among cooccurring bacteria can change the structure and function of a microbial community. However, little is known about the molecular mechanisms that impact such interactions in vivo. We used the association between bioluminescent bacteria and their squid host to study how environmentally transmitted bacteria compete for a limited number of host colonization sites. Our work suggests that Vibrio fischeri use a type VI secretion system, acting as a contact-dependent interbacterial “weapon,” to eliminate competing strains from cooccupying sites in the host. This work illuminates a mechanism by which strain-specific differences drive closely related bacteria to engage in lethal battles as they establish a beneficial symbiosis, revealing how genetic variation among potential colonizers directly impacts the spatial structure of the host-associated population. Intraspecific competition describes the negative interaction that occurs when different populations of the same species attempt to fill the same niche. Such competition is predicted to occur among host-associated bacteria but has been challenging to study in natural biological systems. Although many bioluminescent Vibrio fischeri strains exist in seawater, only a few strains are found in the light-organ crypts of an individual wild-caught Euprymna scolopes squid, suggesting a possible role for intraspecific competition during early colonization. Using a culture-based assay to investigate the interactions of different V. fischeri strains, we found “lethal” and “nonlethal” isolates that could kill or not kill the well-studied light-organ isolate ES114, respectively. The killing phenotype of these lethal strains required a type VI secretion system (T6SS) encoded in a 50-kb genomic island. Multiple lethal and nonlethal strains could be cultured from the light organs of individual wild-caught adult squid. Although lethal strains eliminate nonlethal strains in vitro, two lethal strains could coexist in interspersed microcolonies that formed in a T6SS-dependent manner. This coexistence was destabilized upon physical mixing, resulting in one lethal strain consistently eliminating the other. When juvenile squid were coinoculated with lethal and nonlethal strains, they occupied different crypts, yet they were observed to coexist within crypts when T6SS function was disrupted. These findings, using a combination of natural isolates and experimental approaches in vitro and in the animal host, reveal the importance of T6SS in spatially separating strains during the establishment of host colonization in a natural symbiosis.
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Coryell RL, Turnham KE, de Jesus Ayson EG, Lavilla‐Pltogo C, Alcala AC, Sotto F, Gonzales B, Nishiguchi MK. Phylogeographic patterns in the Philippine archipelago influence symbiont diversity in the bobtail squid -Vibrio mutualism. Ecol Evol 2018; 8:7421-7435. [PMID: 30151160 PMCID: PMC6106162 DOI: 10.1002/ece3.4266] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 04/20/2018] [Accepted: 04/23/2018] [Indexed: 12/05/2022] Open
Abstract
Marine microbes encounter a myriad of biotic and abiotic factors that can impact fitness by limiting their range and capacity to move between habitats. This is especially true for environmentally transmitted bacteria that cycle between their hosts and the surrounding habitat. As geologic history, biogeography, and other factors such as water temperature, salinity, and physical barriers can inhibit bacterial movement to novel environments, we chose to examine the genetic architecture of Euprymna albatrossae (Mollusca: Cephalopoda) and their Vibrio fischeri symbionts in the Philippine archipelago using a combined phylogeographic approach. Eleven separate sites in the Philippine islands were examined using haplotype estimates that were examined via nested clade analysis to determine the relationship between E. albatrossae and V. fischeri populations and their geographic location. Identical analyses of molecular variance (AMOVA) were used to estimate variation within and between populations for host and symbiont genetic data. Host animals demonstrated a significant amount of variation within island groups, while symbiont variation was found within individual populations. Nested clade phylogenetic analysis revealed that hosts and symbionts may have colonized this area at different times, with a sudden change in habitat. Additionally, host data indicate restricted gene flow, whereas symbionts show range expansion, followed by periodic restriction to genetic flow. These differences between host and symbiont networks indicate that factors "outside the squid" influence distribution of Philippine V. fischeri. Our results shed light on how geography and changing environmental factors can impact marine symbiotic associations at both local and global scales.
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Affiliation(s)
- Randy L. Coryell
- Department of BiologyNew Mexico State UniversityLas CrucesNew Mexico
| | - Kira E. Turnham
- Department of BiologyNew Mexico State UniversityLas CrucesNew Mexico
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Evolution of a Vegetarian Vibrio: Metabolic Specialization of Vibrio breoganii to Macroalgal Substrates. J Bacteriol 2018; 200:JB.00020-18. [PMID: 29632094 DOI: 10.1128/jb.00020-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 04/03/2018] [Indexed: 02/07/2023] Open
Abstract
While most Vibrionaceae are considered generalists that thrive on diverse substrates, including animal-derived material, we show that Vibrio breoganii has specialized for the consumption of marine macroalga-derived substrates. Genomic and physiological comparisons of V. breoganii with other Vibrionaceae isolates revealed the ability to degrade alginate, laminarin, and additional glycans present in algal cell walls. Moreover, the widely conserved ability to hydrolyze animal-derived polymers, including chitin and glycogen, was lost, along with the ability to efficiently grow on a variety of amino acids. Ecological data showing associations with particulate algal material but not zooplankton further support this shift in niche preference, and the loss of motility appears to reflect a sessile macroalga-associated lifestyle. Together, these findings indicate that algal polysaccharides have become a major source of carbon and energy in V. breoganii, and these ecophysiological adaptations may facilitate transient commensal associations with marine invertebrates that feed on algae.IMPORTANCE Vibrios are often considered animal specialists or generalists. Here, we show that Vibrio breoganii has undergone massive genomic changes to become specialized on algal carbohydrates. Accompanying genomic changes include massive gene import and loss. These vibrios may help us better understand how algal biomass is degraded in the environment and may serve as a blueprint on how to optimize the conversion of algae to biofuels.
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Tools for Rapid Genetic Engineering of Vibrio fischeri. Appl Environ Microbiol 2018; 84:AEM.00850-18. [PMID: 29776924 DOI: 10.1128/aem.00850-18] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 05/11/2018] [Indexed: 11/20/2022] Open
Abstract
Vibrio fischeri is used as a model for a number of processes, including symbiosis, quorum sensing, bioluminescence, and biofilm formation. Many of these studies depend on generating deletion mutants and complementing them. Engineering such strains, however, is a time-consuming, multistep process that relies on cloning and subcloning. Here, we describe a set of tools that can be used to rapidly engineer deletions and insertions in the V. fischeri chromosome without cloning. We developed a uniform approach for generating deletions using PCR splicing by overlap extension (SOEing) with antibiotic cassettes flanked by standardized linker sequences. PCR SOEing of the cassettes to sequences up- and downstream of the target gene generates a DNA product that can be directly introduced by natural transformation. Selection for the introduced antibiotic resistance marker yields the deletion of interest in a single step. Because these cassettes also contain FRT (FLP recognition target) sequences flanking the resistance marker, Flp recombinase can be used to generate an unmarked, in-frame deletion. We developed a similar methodology and tools for the rapid insertion of specific genes at a benign site in the chromosome for purposes such as complementation. Finally, we generated derivatives of these tools to facilitate different applications, such as inducible gene expression and assessing protein production. We demonstrated the utility of these tools by deleting and inserting genes known or predicted to be involved in motility. While developed for V. fischeri strain ES114, we anticipate that these tools can be adapted for use in other V. fischeri strains and, potentially, other microbes.IMPORTANCEVibrio fischeri is a model organism for studying a variety of important processes, including symbiosis, biofilm formation, and quorum sensing. To facilitate investigation of these biological mechanisms, we developed approaches for rapidly generating deletions and insertions and demonstrated their utility using two genes of interest. The ease, consistency, and speed of the engineering is facilitated by a set of antibiotic resistance cassettes with common linker sequences that can be amplified by PCR with universal primers and fused to adjacent sequences using splicing by overlap extension and then introduced directly into V. fischeri, eliminating the need for cloning and plasmid conjugation. The antibiotic cassettes are flanked by FRT sequences, permitting their removal using Flp recombinase. We augmented these basic tools with a family of constructs for different applications. We anticipate that these tools will greatly accelerate mechanistic studies of biological processes in V. fischeri and potentially other Vibrio species.
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Ongoing Transposon-Mediated Genome Reduction in the Luminous Bacterial Symbionts of Deep-Sea Ceratioid Anglerfishes. mBio 2018; 9:mBio.01033-18. [PMID: 29946051 PMCID: PMC6020299 DOI: 10.1128/mbio.01033-18] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Diverse marine fish and squid form symbiotic associations with extracellular bioluminescent bacteria. These symbionts are typically free-living bacteria with large genomes, but one known lineage of symbionts has undergone genomic reduction and evolution of host dependence. It is not known why distinct evolutionary trajectories have occurred among different luminous symbionts, and not all known lineages previously had genome sequences available. In order to better understand patterns of evolution across diverse bioluminescent symbionts, we de novo sequenced the genomes of bacteria from a poorly studied interaction, the extracellular symbionts from the "lures" of deep-sea ceratioid anglerfishes. Deep-sea anglerfish symbiont genomes are reduced in size by about 50% compared to free-living relatives. They show a striking convergence of genome reduction and loss of metabolic capabilities with a distinct lineage of obligately host-dependent luminous symbionts. These losses include reductions in amino acid synthesis pathways and abilities to utilize diverse sugars. However, the symbiont genomes have retained a number of categories of genes predicted to be useful only outside the host, such as those involved in chemotaxis and motility, suggesting that they may persist in the environment. These genomes contain very high numbers of pseudogenes and show massive expansions of transposable elements, with transposases accounting for 28 and 31% of coding sequences in the symbiont genomes. Transposon expansions appear to have occurred at different times in each symbiont lineage, indicating either independent evolutions of reduction or symbiont replacement. These results suggest ongoing genomic reduction in extracellular luminous symbionts that is facilitated by transposon proliferations.IMPORTANCE Many female deep-sea anglerfishes possess a "lure" containing luminous bacterial symbionts. Here we show that unlike most luminous symbionts, these bacteria are undergoing an evolutionary transition toward small genomes with limited metabolic capabilities. Comparative analyses of the symbiont genomes indicate that this transition is ongoing and facilitated by transposon expansions. This transition may have occurred independently in different symbiont lineages, although it is unclear why. Genomic reduction is common in bacteria that only live within host cells but less common in bacteria that, like anglerfish symbionts, live outside host cells. Since multiple evolutions of genomic reduction have occurred convergently in luminous bacteria, they make a useful system with which to understand patterns of genome evolution in extracellular symbionts. This work demonstrates that ecological factors other than an intracellular lifestyle can lead to dramatic gene loss and evolutionary changes and that transposon expansions may play important roles in this process.
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Freese HM, Sikorski J, Bunk B, Scheuner C, Meier-Kolthoff JP, Spröer C, Gram L, Overmann J. Trajectories and Drivers of Genome Evolution in Surface-Associated Marine Phaeobacter. Genome Biol Evol 2018; 9:3297-3311. [PMID: 29194520 PMCID: PMC5730936 DOI: 10.1093/gbe/evx249] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/27/2017] [Indexed: 12/19/2022] Open
Abstract
The extent of genome divergence and the evolutionary events leading to speciation of marine bacteria have mostly been studied for (locally) abundant, free-living groups. The genus Phaeobacter is found on different marine surfaces, seems to occupy geographically disjunct habitats, and is involved in different biotic interactions, and was therefore targeted in the present study. The analysis of the chromosomes of 32 closely related but geographically spread Phaeobacter strains revealed an exceptionally large, highly syntenic core genome. The flexible gene pool is constantly but slightly expanding across all Phaeobacter lineages. The horizontally transferred genes mostly originated from bacteria of the Roseobacter group and horizontal transfer most likely was mediated by gene transfer agents. No evidence for geographic isolation and habitat specificity of the different phylogenomic Phaeobacter clades was detected based on the sources of isolation. In contrast, the functional gene repertoire and physiological traits of different phylogenomic Phaeobacter clades were sufficiently distinct to suggest an adaptation to an associated lifestyle with algae, to additional nutrient sources, or toxic heavy metals. Our study reveals that the evolutionary trajectories of surface-associated marine bacteria can differ significantly from free-living marine bacteria or marine generalists.
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Affiliation(s)
- Heike M Freese
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Johannes Sikorski
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Boyke Bunk
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Carmen Scheuner
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Jan P Meier-Kolthoff
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Cathrin Spröer
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany
| | - Lone Gram
- Department of Biotechnology and Bioengineering, Technical University of Denmark, Lyngby, Denmark
| | - Jörg Overmann
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen, Braunschweig, Germany.,Institute of Microbiology, University Braunschweig, Germany
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Reproductive System Symbiotic Bacteria Are Conserved between Two Distinct Populations of Euprymna scolopes from Oahu, Hawaii. mSphere 2018; 3:mSphere00531-17. [PMID: 29600280 PMCID: PMC5874440 DOI: 10.1128/msphere.00531-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 02/26/2018] [Indexed: 02/04/2023] Open
Abstract
In this study, we examined the reproductive ANG symbiosis found in two genetically isolated populations of the Hawaiian bobtail squid, Euprymna scolopes. The stability of the community reported here provides support for the hypothesis that this symbiosis is under strong selective pressure, while the observed differences suggest that some level of local adaptation may have occurred. These two host populations are frequently used interchangeably as source populations for research. Euprymna scolopes is an important model organism and offers the opportunity to examine the interplay between a binary and a consortial symbiosis in a single model host. Understanding the inherent natural variability of this association will aid in our understanding of the conservation, function, transmission, and development of the ANG symbiosis. Female Hawaiian bobtail squid, Euprymna scolopes, harbor a symbiotic bacterial community in a reproductive organ, the accessory nidamental gland (ANG). This community is known to be stable over several generations of wild-caught bobtail squid but has, to date, been examined for only one population in Maunalua Bay, Oahu, HI. This study assessed the ANG and corresponding egg jelly coat (JC) bacterial communities for another genetically isolated host population from Kaneohe Bay, Oahu, HI, using 16S amplicon sequencing. The bacterial communities from the ANGs and JCs of the two populations were found to be similar in richness, evenness, phylogenetic diversity, and overall community composition. However, the Kaneohe Bay samples formed their own subset within the Maunalua Bay ANG/JC community. An Alteromonadaceae genus, BD2-13, was significantly higher in relative abundance in the Kaneohe Bay population, and several Alphaproteobacteria taxa also shifted in relative abundance between the two groups. This variation could be due to local adaptation to differing environmental challenges, to localized variability, or to functional redundancy among the ANG taxa. The overall stability of the community between the populations further supports a crucial functional role that has been hypothesized for this symbiosis. IMPORTANCE In this study, we examined the reproductive ANG symbiosis found in two genetically isolated populations of the Hawaiian bobtail squid, Euprymna scolopes. The stability of the community reported here provides support for the hypothesis that this symbiosis is under strong selective pressure, while the observed differences suggest that some level of local adaptation may have occurred. These two host populations are frequently used interchangeably as source populations for research. Euprymna scolopes is an important model organism and offers the opportunity to examine the interplay between a binary and a consortial symbiosis in a single model host. Understanding the inherent natural variability of this association will aid in our understanding of the conservation, function, transmission, and development of the ANG symbiosis.
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Phylogenomic analysis demonstrates a pattern of rare and long-lasting concerted evolution in prokaryotes. Commun Biol 2018; 1:12. [PMID: 30271899 PMCID: PMC6053082 DOI: 10.1038/s42003-018-0014-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 01/11/2018] [Indexed: 12/15/2022] Open
Abstract
Concerted evolution, where paralogs in the same species show higher sequence similarity to each other than to orthologs in other species, is widely found in many species. However, cases of concerted evolution that last for hundreds of millions of years are very rare. By genome-wide analysis of a broad selection of prokaryotes, we provide strong evidence of recurrent concerted evolution in 26 genes, most of which have lasted more than ~500 million years. We find that most concertedly evolving genes are key members of important pathways, and encode proteins from the same complexes and/or pathways, suggesting coevolution of genes via concerted evolution to maintain gene balance. We also present LRCE-DB, a comprehensive online repository of long-lasting concerted evolution. Collectively, our study reveals that although most duplicated genes may diverge in sequence over a long period, on rare occasions this constraint can be breached, leading to unexpected long-lasting concerted evolution in a recurrent manner. Sishuo Wang and Youhua Chen present an analysis of concerted evolution in prokaryotes using a new computational pipeline, iSeeCE. They find evidence in 26 genes for recurrent concerted evolution, most of which last more than ~500 million years, and provide a database, LRCE-DB, for data exploration.
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Freese HM, Methner A, Overmann J. Adaptation of Surface-Associated Bacteria to the Open Ocean: A Genomically Distinct Subpopulation of Phaeobacter gallaeciensis Colonizes Pacific Mesozooplankton. Front Microbiol 2017; 8:1659. [PMID: 28912769 PMCID: PMC5583230 DOI: 10.3389/fmicb.2017.01659] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 08/16/2017] [Indexed: 02/03/2023] Open
Abstract
The marine Roseobacter group encompasses numerous species which occupy a large variety of ecological niches. However, members of the genus Phaeobacter are specifically adapted to a surface-associated lifestyle and have so far been found nearly exclusively in disjunct, man-made environments including shellfish and fish aquacultures, as well as harbors. Therefore, the possible natural habitats, dispersal and evolution of Phaeobacter spp. have largely remained obscure. Applying a high-throughput cultivation strategy along a longitudinal Pacific transect, the present study revealed for the first time a widespread natural occurrence of Phaeobacter in the marine pelagial. These bacteria were found to be specifically associated to mesoplankton where they constitute a small but detectable proportion of the bacterial community. The 16S rRNA gene sequences of 18 isolated strains were identical to that of Phaeobacter gallaeciensis DSM26640T but sequences of internal transcribed spacer and selected genomes revealed that the strains form a distinct clade within P. gallaeciensis. The genomes of the Pacific and the aquaculture strains were highly conserved and had a fraction of the core genome of 89.6%, 80 synteny breakpoints, and differed 2.2% in their nucleotide sequences. Diversification likely occurred through neutral mutations. However, the Pacific strains exclusively contained two active Type I restriction modification systems which is commensurate with a reduced acquisition of mobile elements in the Pacific clade. The Pacific clade of P. gallaeciensis also acquired a second, homolog phosphonate transport system compared to all other P. gallaeciensis. Our data indicate that a previously unknown, distinct clade of P. gallaeciensis acquired a limited number of clade-specific genes that were relevant for its association with mesozooplankton and for colonization of the marine pelagial. The divergence of the Pacific clade most likely was driven by the adaptation to this novel ecological niche rather than by geographic isolation.
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Affiliation(s)
- Heike M Freese
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und ZellkulturenBraunschweig, Germany
| | - Anika Methner
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und ZellkulturenBraunschweig, Germany
| | - Jörg Overmann
- Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und ZellkulturenBraunschweig, Germany
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Experimental Evaluation of Host Adaptation of Lactobacillus reuteri to Different Vertebrate Species. Appl Environ Microbiol 2017; 83:AEM.00132-17. [PMID: 28389535 DOI: 10.1128/aem.00132-17] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Accepted: 03/28/2017] [Indexed: 11/20/2022] Open
Abstract
The species Lactobacillus reuteri has diversified into host-specific lineages, implying a long-term association with different vertebrates. Strains from rodent lineages show specific adaptations to mice, but the processes underlying the evolution of L. reuteri in other hosts remain unknown. We administered three standardized inocula composed of strains from different host-confined lineages to mice, pigs, chickens, and humans. The ecological performance of each strain in the gastrointestinal tract of each host was determined by typing random colonies recovered from fecal samples collected over five consecutive days postadministration. Results revealed that rodent strains were predominant in mice, confirming previous findings of host adaptation. In chickens, poultry strains of the lineage VI (poultry VI) and human isolates from the same lineage (human VI) were recovered at the highest and second highest rates, respectively. Interestingly, human VI strains were virtually undetected in human feces. These findings, together with ancestral state reconstructions, indicate poultry VI and human VI strains share an evolutionary history with chickens. Genomic analysis revealed that poultry VI strains possess a large and variable accessory genome, whereas human VI strains display low genetic diversity and possess genes encoding antibiotic resistance and capsular polysaccharide synthesis, which might have allowed temporal colonization of humans. Experiments in pigs and humans did not provide evidence of host adaptation of L. reuteri to these hosts. Overall, our findings demonstrate host adaptation of L. reuteri to rodents and chickens, supporting a joint evolution of this bacterial species with several vertebrate hosts, although questions remain about its natural history in humans and pigs.IMPORTANCE Gut microbes are often hypothesized to have coevolved with their vertebrate hosts. However, the evidence is sparse and the evolutionary mechanisms have not been identified. We developed and applied an experimental approach to determine host adaptation of L. reuteri to different hosts. Our findings confirmed adaptation to rodents and provided evidence of adaptation to poultry, suggesting that L. reuteri evolved via natural selection in different hosts. By complementing phylogenetic analyses with experimental evidence, this study provides novel information about the mechanisms driving host-microbe coevolution with vertebrates and serve as a basis to inform the application of L. reuteri as a probiotic for different host species.
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Pan S, Nikolakakis K, Adamczyk PA, Pan M, Ruby EG, Reed JL. Model-enabled gene search (MEGS) allows fast and direct discovery of enzymatic and transport gene functions in the marine bacterium Vibrio fischeri. J Biol Chem 2017; 292:10250-10261. [PMID: 28446608 DOI: 10.1074/jbc.m116.763193] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 04/23/2017] [Indexed: 12/23/2022] Open
Abstract
Whereas genomes can be rapidly sequenced, the functions of many genes are incompletely or erroneously annotated because of a lack of experimental evidence or prior functional knowledge in sequence databases. To address this weakness, we describe here a model-enabled gene search (MEGS) approach that (i) identifies metabolic functions either missing from an organism's genome annotation or incorrectly assigned to an ORF by using discrepancies between metabolic model predictions and experimental culturing data; (ii) designs functional selection experiments for these specific metabolic functions; and (iii) selects a candidate gene(s) responsible for these functions from a genomic library and directly interrogates this gene's function experimentally. To discover gene functions, MEGS uses genomic functional selections instead of relying on correlations across large experimental datasets or sequence similarity as do other approaches. When applied to the bioluminescent marine bacterium Vibrio fischeri, MEGS successfully identified five genes that are responsible for four metabolic and transport reactions whose absence from a draft metabolic model of V. fischeri caused inaccurate modeling of high-throughput experimental data. This work demonstrates that MEGS provides a rapid and efficient integrated computational and experimental approach for annotating metabolic genes, including those that have previously been uncharacterized or misannotated.
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Affiliation(s)
- Shu Pan
- From the Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Kiel Nikolakakis
- From the Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Paul A Adamczyk
- From the Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Min Pan
- the School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China, and
| | - Edward G Ruby
- the Pacific Biosciences Research Center, University of Hawaii, Manoa, Hawaii 96813
| | - Jennifer L Reed
- From the Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706,
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