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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 19 (1980), S. 4989-4993 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 27 (1988), S. 2624-2629 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Vibrio fischeri is the bacterial symbiont within the light-emitting organ of the sepiolid squid Euprymna scolopes . Upon colonizing juvenile squids, bacterial symbionts grow on host-supplied nutrients, while providing a bioluminescence that the host uses during its nocturnal activities. Mutant bacterial strains that are unable to emit light have been shown to be defective in normal colonization. A 606 bp open reading frame was cloned from V. fischeri that encoded a protein, which we named LitR, that had about 60% identity to four related regulator proteins: Vibrio cholerae HapR, Vibrio harveyi LuxR, Vibrio parahaemolyticus OpaR and Vibrio vulnificus SmcR. When grown in culture, cells of V. fischeri strain PMF8, in which litR was insertionally inactivated, were delayed in the onset of luminescence induction and emitted only about 20% as much light per cell as its parent. Protein-binding studies suggested that LitR enhances quorum sensing by regulating the transcription of the luxR gene. Interestingly, when competed against its parent in mixed inocula, PMF8 became the predominant symbiont present in 83% of light organs. Thus, the litR mutation appears to represent a novel class of mutations in which the loss of a regulatory gene function enhances the bacterium's competence in initiating a benign infection.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 50 (1996), S. 591-624 
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract Although the study of microbe-host interactions has been traditionally dominated by an interest in pathogenic associations, there is an increasing awareness of the importance of cooperative symbiotic interactions in the biology of many bacteria and their animal and plant hosts. This review examines a model system for the study of such symbioses, the light organ association between the bobtail squid Euprymna scolopes and the marine luminous bacterium Vibrio fischeri. Specifically, the initiation, establishment, and persistence of the benign bacterial infection of the juvenile host light organ are described, as are efforts to understand the mechanisms underlying this specific colonization program. Using molecular genetic techniques, mutant strains of V. fischeri have been constructed that are defective at specific stages of the development of the association. Some of the lessons that these mutants have begun to teach us about the complex and long-term nature of this cooperative venture are summarized.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 48 (2003), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Quorum-sensing control of luminescence in Vibrio harveyi, which involves an indirect autoinducer-mediated phosphorelay signal transduction system, contrasts with the prototypical quorum-sensing system of Vibrio fischeri, in which the autoinducer and the transcriptional activator LuxR directly activate lux operon expression. In V. harveyi, a regulator not homologous to V. fischeri LuxR and also designated LuxR (LuxRvh), binds specifically to the lux operon promoter region and activates the expression of luminescence. A direct connection has not been identified previously between V. harveyi LuxRvh and the autoinducer-mediated phosphorelay system. Here, we demonstrate by mobility shift assays and measurement of luxRvh mRNA levels with luxO+ and luxO– cells that the central response regulator of the V. harveyi phosphorelay system (LuxO) represses the level of LuxRvh. Expression of a luxRvh-bearing plasmid strongly stimulated luminescence of a luxO– mutant but had no effect on luminescence of wild-type luxO+ cells, indicating tight regulation of luxRvh by LuxO. Furthermore, luxO null mutants of V. fischeri MJ-1 and two autoinducer mutants, MJ-211 (luxI–) and MJ-215 (luxI–ainS–), emitted more light and exhibited more elevated levels of litR, a newly identified V. harveyi luxRvh homologue, than their luxO+ counterparts. These results suggest that activity of the autoinducer-mediated phosphorelay system is coupled to LuxRvh/LitR control of luminescence through LuxO in V. harveyi and V. fischeri. The presence of homologues of V. harveyi LuxRvh, LuxO and other phosphorelay system proteins in various Vibrio species and the control of LuxRvh and its homologues by LuxO identified here in V. harveyi and V. fischeri and recently in Vibrio cholerae suggest that the luxO–luxRvh couple is a central feature of this quorum-sensing system in members of the genus Vibrio.
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacterial quorum sensing using acyl-homoserine lactones (acyl-HSLs) as cell-density dependent signalling molecules is important for the transcriptional regulation of many genes essential in the establishment and the maintenance of bacteria–host associations. Vibrio fischeri, the symbiotic partner of the Hawaiian bobtail squid Euprymna scolopes, possesses two distinct acyl-HSL synthase proteins, LuxI and AinS. Whereas the cell density-dependent regulation of luminescence by the LuxI-produced signal is a well-described phenomenon, and its role in light organ symbiosis has been defined, little is known about the ain system. We have investigated the impact of the V. fischeri acyl-HSL synthase AinS on both luminescence and symbiotic colonization. Through phenotypic studies of V. fischeri mutants we have found that the AinS-signal is the predominant inducer of luminescence expression in culture, whereas the impact of the LuxI-signal is apparent only at the high cell densities occurring in symbiosis. Furthermore, our studies revealed that ainS regulates activities essential for successful colonization of E. scolopes, i.e. the V. fischeri ainS mutant failed to persist in the squid light organ. Mutational inactivation of the transcriptional regulator protein LuxO in the ainS mutant partially or completely reversed all the observed phenotypes, demonstrating that the AinS-signal regulates expression of downstream genes through the inactivation of LuxO. Taken together, our results suggest that the two quorum-sensing systems in V. fischeri, ain and lux, sequentially induce the expression of luminescence genes and possibly other colonization factors.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Current microbiology 29 (1994), S. 279-286 
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Because of the importance of plasmids in many bacterial associations with plants and animals, we determined the occurrence and distribution of plasmid DNA in symbioticVibrio fischeri from the light organ of the sepiolid squidEuprymna scolopes. Analyses of 225 isolates of symbioticV. fischeri from 25 individual squids revealed an overall plasmid-carriage rate of 56%. A large plasmid (≥39 kb) was detected in 96% of those isolates carrying plasmids, and multiple small plasmids were found to co-occur with one of the large plasmids in 81% of plasmid-carrying strains. In addition, these plasmids appear to be restricted toV. fischeri strains isolated fromE. scolopes and from seawater at sites of squid populations. We were unable to assign a role or function to these plasmids, but they do not carry genes required for the establishment of the light organ symbiosis. We conclude that the essential bacterial symbiotic determinants must be encoded on the chromosome and that the plasmids may carry genes that are important for the survival of theseV. fischeri strains outside of the symbiotic association.
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  • 8
    Publication Date: 2010-01-19
    Description: Mechanisms for controlling symbiont populations are critical for maintaining the associations that exist between a host and its microbial partners. We describe here the transcriptional, metabolic, and ultrastructural characteristics of a diel rhythm that occurs in the symbiosis between the squid Euprymna scolopes and the luminous bacterium Vibrio fischeri. The rhythm is driven by the host’s expulsion from its light-emitting organ of most of the symbiont population each day at dawn. The transcriptomes of both the host epithelium that supports the symbionts and the symbiont population itself were characterized and compared at four times over this daily cycle. The greatest fluctuation in gene expression of both partners occurred as the day began. Most notable was an up-regulation in the host of 〉50 cytoskeleton-related genes just before dawn and their subsequent down-regulation within 6 h. Examination of the epithelium by TEM revealed a corresponding restructuring, characterized by effacement and blebbing of its apical surface. After the dawn expulsion, the epithelium reestablished its polarity, and the residual symbionts began growing, repopulating the light organ. Analysis of the symbiont transcriptome suggested that the bacteria respond to the effacement by up-regulating genes associated with anaerobic respiration of glycerol; supporting this finding, lipid analysis of the symbionts’ membranes indicated a direct incorporation of host-derived fatty acids. After 12 h, the metabolic signature of the symbiont population shifted to one characteristic of chitin fermentation, which continued until the following dawn. Thus, the persistent maintenance of the squid–vibrio symbiosis is tied to a dynamic diel rhythm that involves both partners.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2016-03-14
    Description: Although it is known that diverse bacterial flagellar motors produce different torques, the mechanism underlying torque variation is unknown. To understand this difference better, we combined genetic analyses with electron cryo-tomography subtomogram averaging to determine in situ structures of flagellar motors that produce different torques, fromCampylobacterandVibriospecies. For the first time, to our knowledge, our results unambiguously locate the torque-generating stator complexes and show that diverse high-torque motors use variants of an ancestrally related family of structures to scaffold incorporation of additional stator complexes at wider radii from the axial driveshaft than in the model enteric motor. We identify the protein components of these additional scaffold structures and elucidate their sequential assembly, demonstrating that they are required for stator-complex incorporation. These proteins are widespread, suggesting that different bacteria have tailored torques to specific environments by scaffolding alternative stator placement and number. Our results quantitatively account for different motor torques, complete the assignment of the locations of the major flagellar components, and provide crucial constraints for understanding mechanisms of torque generation and the evolution of multiprotein complexes.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2019-03-04
    Description: The colonization of an animal’s tissues by its microbial partners creates networks of communication across the host’s body. We used the natural binary light-organ symbiosis between the squid Euprymna scolopes and its luminous bacterial partner, Vibrio fischeri, to define the impact of colonization on transcriptomic networks in the host. A night-active predator, E. scolopes coordinates the bioluminescence of its symbiont with visual cues from the environment to camouflage against moon and starlight. Like mammals, this symbiosis has a complex developmental program and a strong day/night rhythm. We determined how symbiont colonization impacted gene expression in the light organ itself, as well as in two anatomically remote organs: the eye and gill. While the overall transcriptional signature of light organ and gill were more alike, the impact of symbiosis was most pronounced and similar in light organ and eye, both in juvenile and adult animals. Furthermore, the presence of a symbiosis drove daily rhythms of transcription within all three organs. Finally, a single mutation in V. fischeri—specifically, deletion of the lux operon, which abrogates symbiont luminescence—reduced the symbiosis-dependent transcriptome of the light organ by two-thirds. In addition, while the gills responded similarly to light-organ colonization by either the wild-type or mutant, luminescence was required for all of the colonization-associated transcriptional responses in the juvenile eye. This study defines not only the impact of symbiont colonization on the coordination of animal transcriptomes, but also provides insight into how such changes might impact the behavior and ecology of the host.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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