Phylogeny and fitness of Vibrio fischeri from the light organs of Euprymna scolopes in two Oahu, Hawaii populations

ABSTRACT Trimethylamine N-oxide (TMAO) reductases are widespread in bacteria and often function in anaerobic respiration. The regulation and expression of TMAO reductase operons have been well studied in model genera such as Escherichia, Shewanella, and Rhodobacter, although TMAO reductases are present in many other bacteria, including the marine Vibrio species. The genome sequence of Vibrio fischeri revealed three putative TMAO reductase operons, and a previous report identified TMAO reductase activity in symbiotic V. fischeri isolates associated with the light organs of adult Hawaiian bobtail squid, Euprymna scolopes. We examined the roles and regulation of these three operons using mutational analyses and promoter-reporter fusions. We found that the torECA promoter, and to a lesser extent the torYZ and dmsABC promoters, were active during symbiotic colonization of juvenile E. scolopes; however, a V. fischeri strain lacking TMAO reductase activity displays no discernible colonization defect over the first 48 h. Our studies also revealed that torECA has the most active promoter of the putative TMAO reductase operons, and TorECA is the major contributor to TMAO-dependent growth in V. fischeri under the conditions tested. Interestingly, the transcriptional regulation of TMAO reductase operons in V. fischeri appears to differ from that in previously studied organisms, such as Escherichia coli, which may reflect differences in gene arrangement and bacterial habitat. This study lays the foundation for using V. fischeri as a model system for studying TMAO reductases in the Vibrionaceae.

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A New Niche for Vibrio logei, the Predominant Light Organ Symbiont of Squids in the GenusSepiola

Journal of Bacteriology ◽

10.1128/jb.180.1.59-64.1998 ◽

1998 ◽

Vol 180 (1) ◽

pp. 59-64 ◽

Cited By ~ 68

Author(s):

Pat M. Fidopiastis ◽

Sigurd von Boletzky ◽

Edward G. Ruby

Keyword(s):

Coastal Waters ◽

Vibrio Fischeri ◽

Aliphatic Aldehyde ◽

Mixed Population ◽

Light Organ ◽

Euprymna Scolopes ◽

Light Organs ◽

Luminous Bacteria ◽

Animal Hosts ◽

The Western Pacific

ABSTRACT Two genera of sepiolid squids—Euprymna, found primarily in shallow, coastal waters of Hawaii and the Western Pacific, and Sepiola, the deeper-, colder-water-dwelling Mediterranean and Atlantic squids—are known to recruit luminous bacteria into light organ symbioses. The light organ symbiont ofEuprymna spp. is Vibrio fischeri, but until now, the light organ symbionts of Sepiola spp. have remained inadequately identified. We used a combination of molecular and physiological characteristics to reveal that the light organs ofSepiola affinis and Sepiola robusta contain a mixed population of Vibrio logei and V. fischeri, with V. logei comprising between 63 and 100% of the bacteria in the light organs that we analyzed. V. logei had not previously been known to exist in such symbioses. In addition, this is the first report of two different species of luminous bacteria co-occurring within a single light organ. The luminescence of these symbiotic V. logei strains, as well as that of other isolates of V. logei tested, is reduced when they are grown at temperatures above 20°C, partly due to a limitation in the synthesis of aliphatic aldehyde, a substrate of the luminescence reaction. In contrast, the luminescence of the V. fischeri symbionts is optimal above 24°C and is not enhanced by aldehyde addition. Also, V. fischeri strains were markedly more successful than V. logei at colonizing the light organs of juvenile Euprymna scolopes, especially at 26°C. These findings have important implications for our understanding of the ecological dynamics and evolution of cooperative, and perhaps pathogenic, associations of Vibrio spp. with their animal hosts.

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Population Structure of Vibrio fischeri within the Light Organs of Euprymna scolopes Squid from Two Oahu (Hawaii) Populations

Applied and Environmental Microbiology ◽

10.1128/aem.01792-08 ◽

2008 ◽

Vol 75 (1) ◽

pp. 193-202 ◽

Cited By ~ 68

Author(s):

M. S. Wollenberg ◽

E. G. Ruby

Keyword(s):

Population Structure ◽

Vibrio Fischeri ◽

Population Data ◽

Intraspecific Diversity ◽

Light Organ ◽

Euprymna Scolopes ◽

Individual Host ◽

Light Organs ◽

Sepiolid Squid ◽

The Stability

ABSTRACT We resolved the intraspecific diversity of Vibrio fischeri, the bioluminescent symbiont of the Hawaiian sepiolid squid Euprymna scolopes, at two previously unexplored morphological and geographical scales. These scales ranged from submillimeter regions within the host light organ to the several kilometers encompassing two host populations around Oahu. To facilitate this effort, we employed both novel and standard genetic and phenotypic assays of light-organ symbiont populations. A V. fischeri-specific fingerprinting method and five phenotypic assays were used to gauge the genetic richness of V. fischeri populations; these methods confirmed that the symbiont population present in each adult host's light organ is polyclonal. Upon statistical analysis of these genetic and phenotypic population data, we concluded that the characteristics of symbiotic populations were more similar within individual host populations than between the two distinct Oahu populations of E. scolopes, providing evidence that local geographic symbiont population structure exists. Finally, to better understand the genesis of symbiont diversity within host light organs, the process of symbiosis initiation in newly hatched juvenile squid was examined both experimentally and by mathematical modeling. We concluded that, after the juvenile hatches, only one or two cells of V. fischeri enter each of six internal epithelium-lined crypts present in the developing light organ. We hypothesize that the expansion of different, crypt-segregated, clonal populations creates the polyclonal adult light-organ population structure observed in this study. The stability of the luminous-bacterium-sepiolid squid mutualism in the presence of a polyclonal symbiont population structure is discussed in the context of contemporary evolutionary theory.

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Host-selected mutations converging on a global regulator drive an adaptive leap towards symbiosis in bacteria

eLife ◽

10.7554/elife.24414 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 21

Author(s):

M Sabrina Pankey ◽

Randi L Foxall ◽

Ian M Ster ◽

Lauren A Perry ◽

Brian M Schuster ◽

...

Keyword(s):

Genetic Basis ◽

Vibrio Fischeri ◽

Selective Advantage ◽

Host Defenses ◽

Euprymna Scolopes ◽

Global Regulator ◽

Kinase Gene ◽

Selective Agents ◽

Light Organs ◽

Physical Barriers

Host immune and physical barriers protect against pathogens but also impede the establishment of essential symbiotic partnerships. To reveal mechanisms by which beneficial organisms adapt to circumvent host defenses, we experimentally evolved ecologically distinct bioluminescent Vibrio fischeri by colonization and growth within the light organs of the squid Euprymna scolopes. Serial squid passaging of bacteria produced eight distinct mutations in the binK sensor kinase gene, which conferred an exceptional selective advantage that could be demonstrated through both empirical and theoretical analysis. Squid-adaptive binK alleles promoted colonization and immune evasion that were mediated by cell-associated matrices including symbiotic polysaccharide (Syp) and cellulose. binK variation also altered quorum sensing, raising the threshold for luminescence induction. Preexisting coordinated regulation of symbiosis traits by BinK presented an efficient solution where altered BinK function was the key to unlock multiple colonization barriers. These results identify a genetic basis for microbial adaptability and underscore the importance of hosts as selective agents that shape emergent symbiont populations.

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FlrA, a σ54-Dependent Transcriptional Activator in Vibrio fischeri, Is Required for Motility and Symbiotic Light-Organ Colonization

Journal of Bacteriology ◽

10.1128/jb.185.12.3547-3557.2003 ◽

2003 ◽

Vol 185 (12) ◽

pp. 3547-3557 ◽

Cited By ~ 47

Author(s):

Deborah S. Millikan ◽

Edward G. Ruby

Keyword(s):

Vibrio Fischeri ◽

Transcriptional Activator ◽

Pcr Analysis ◽

Euprymna Scolopes ◽

Wild Type ◽

Flagellar Regulon ◽

Colonization Factors ◽

Recognition Motifs ◽

Arbitrarily Primed Pcr ◽

Organ Colonization

ABSTRACT Flagellum-mediated motility of Vibrio fischeri is an essential factor in the bacterium's ability to colonize its host, the Hawaiian squid Euprymna scolopes. To begin characterizing the nature of the flagellar regulon, we have cloned a gene, designated flrA, from V. fischeri that encodes a putative σ54-dependent transcriptional activator. Genetic arrangement of the flrA locus in V. fischeri is similar to motility master-regulator operons of Vibrio cholerae and Vibrio parahaemolyticus. In addition, examination of regulatory regions of a number of flagellar operons in V. fischeri revealed apparent σ54 recognition motifs, suggesting that the flagellar regulatory hierarchy is controlled by a similar mechanism to that described in V. cholerae. However, in contrast to its closest known relatives, flrA mutant strains of V. fischeri ES114 were completely abolished in swimming capability. Although flrA provided in trans restored motility to the flrA mutant, the complemented strain was unable to reach wild-type levels of symbiotic colonization in juvenile squid, suggesting a possible role for the proper expression of FlrA in regulating symbiotic colonization factors in addition to those required for motility. Comparative RNA arbitrarily primed PCR analysis of the flrA mutant and its wild-type parent revealed several differentially expressed transcripts. These results define a regulon that includes both flagellar structural genes and other genes apparently not involved in flagellum elaboration or function. Thus, the transcriptional activator FlrA plays an essential role in regulating motility, and apparently in modulating other symbiotic functions, in V. fischeri.

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Is the Vibrio fischeri-;Euprymna scolopes Symbiosis a Defensive Mutualism?

Mycology - Defensive Mutualism in Microbial Symbiosis ◽

10.1201/9781420069327.ch6 ◽

2009 ◽

Cited By ~ 5

Author(s):

Eric Stabb ◽

Deborah Millikan

Keyword(s):

Vibrio Fischeri ◽

Euprymna Scolopes ◽

Defensive Mutualism

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Adaptation to temperature stress by Vibrio fischeri facilitates this microbe's symbiosis with the Hawaiian bobtail squid ( Euprymna scolopes )

Evolution ◽

10.1111/evo.13819 ◽

2019 ◽

Vol 73 (9) ◽

pp. 1885-1897 ◽

Cited By ~ 1

Author(s):

Meagan Leah Cohen ◽

Ekaterina Vadimovna Mashanova ◽

Nicholas Matthew Rosen ◽

William Soto

Keyword(s):

Temperature Stress ◽

Vibrio Fischeri ◽

Euprymna Scolopes

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Correlation between Osmolarity and Luminescence of Symbiotic Vibrio fischeri Strain ES114

Journal of Bacteriology ◽

10.1128/jb.186.9.2906-2908.2004 ◽

2004 ◽

Vol 186 (9) ◽

pp. 2906-2908 ◽

Cited By ~ 27

Author(s):

Eric V. Stabb ◽

Melissa S. Butler ◽

Dawn M. Adin

Keyword(s):

Vibrio Fischeri ◽

Culture Media ◽

Light Output ◽

Euprymna Scolopes ◽

Low Light ◽

Luminescence Enhancement ◽

High Level

ABSTRACT Vibrio fischeri isolates from Euprymna scolopes are dim in culture but bright in the host. We found the luminescence of V. fischeri to be correlated with external osmolarity both in culture and in this symbiosis. Luminescence enhancement by osmolarity was independent of the lux promoter and unaffected by autoinducers or the level of lux expression, but the addition of an aldehyde substrate for luciferase raised the luminescence of cells grown at high and low osmolarities to the same high level. V. fischeri culture media have lower osmolarities than are typical in seawater or in cephalopods, partially accounting for the bacterium's low light output in culture.

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Characterization of htrB and msbB Mutants of the Light Organ Symbiont Vibrio fischeri

Applied and Environmental Microbiology ◽

10.1128/aem.02138-07 ◽

2007 ◽

Vol 74 (3) ◽

pp. 633-644 ◽

Cited By ~ 15

Author(s):

Dawn M. Adin ◽

Nancy J. Phillips ◽

Bradford W. Gibson ◽

Michael A. Apicella ◽

Edward G. Ruby ◽

...

Keyword(s):

Lipid A ◽

Vibrio Fischeri ◽

Sodium Dodecyl ◽

Chromosome 1 ◽

Chromosome 2 ◽

Euprymna Scolopes ◽

Host Interactions ◽

Lipid A Structure ◽

Bacterial Lipid

ABSTRACT Bacterial lipid A is an important mediator of bacterium-host interactions, and secondary acylations added by HtrB and MsbB can be critical for colonization and virulence in pathogenic infections. In contrast, Vibrio fischeri lipid A stimulates normal developmental processes in this bacterium's mutualistic host, Euprymna scolopes, although the importance of lipid A structure in this symbiosis is unknown. To further examine V. fischeri lipid A and its symbiotic function, we identified two paralogs of htrB (designated htrB1 and htrB2) and an msbB gene in V. fischeri ES114 and demonstrated that these genes encode lipid A secondary acyltransferases. htrB2 and msbB are found on the Vibrio “housekeeping” chromosome 1 and are conserved in other Vibrio species. Mutations in htrB2 and msbB did not impair symbiotic colonization but resulted in phenotypic alterations in culture, including reduced motility and increased luminescence. These mutations also affected sensitivity to sodium dodecyl sulfate, kanamycin, and polymyxin, consistent with changes in membrane permeability. Conversely, htrB1 is located on the smaller, more variable vibrio chromosome 2, and an htrB1 mutant was wild-type-like in culture but appeared attenuated in initiating the symbiosis and was outcompeted 2.7-fold during colonization when mixed with the parent. These data suggest that htrB2 and msbB play conserved general roles in vibrio biology, whereas htrB1 plays a more symbiosis-specific role in V. fischeri.

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An Expanded Transposon Mutant Library Reveals that Vibrio fischeri δ-Aminolevulinate Auxotrophs Can Colonize Euprymna scolopes

Applied and Environmental Microbiology ◽

10.1128/aem.02470-16 ◽

2016 ◽

Vol 83 (5) ◽

Cited By ~ 6

Author(s):

Noreen L. Lyell ◽

Alecia N. Septer ◽

Anne K. Dunn ◽

Drew Duckett ◽

Julie L. Stoudenmire ◽

...

Keyword(s):

Vibrio Fischeri ◽

Light Organ ◽

Mutant Library ◽

Euprymna Scolopes ◽

Simple Method ◽

Content Type ◽

Transposon Insertion ◽

Rich Media ◽

Show Evidence

ABSTRACT Libraries of defined mutants are valuable research tools but necessarily lack gene knockouts that are lethal under the conditions used in library construction. In this study, we augmented a Vibrio fischeri mutant library generated on a rich medium (LBS, which contains [per liter] 10 g of tryptone, 5 g of yeast extract, 20 g of NaCl, and 50 mM Tris [pH 7.5]) by selecting transposon insertion mutants on supplemented LBS and screening for those unable to grow on LBS. We isolated strains with insertions in alr, glr (murI), glmS, several heme biosynthesis genes, and ftsA, as well as a mutant disrupted 14 bp upstream of ftsQ. Mutants with insertions in ftsA or upstream of ftsQ were recovered by addition of Mg2+ to LBS, but their cell morphology and motility were affected. The ftsA mutant was more strongly affected and formed cells or chains of cells that appeared to wind back on themselves helically. Growth of mutants with insertions in glmS, alr, or glr was recovered with N-acetylglucosamine (NAG), d-alanine, or d-glutamate, respectively. We hypothesized that NAG, d-alanine, or d-glutamate might be available to V. fischeri in the Euprymna scolopes light organ; however, none of these mutants colonized the host effectively. In contrast, hemA and hemL mutants, which are auxotrophic for δ-aminolevulinate (ALA), colonized at wild-type levels, although mutants later in the heme biosynthetic pathway were severely impaired or unable to colonize. Our findings parallel observations that legume hosts provide Bradyrhizobium symbionts with ALA, but they contrast with virulence phenotypes of hemA mutants in some pathogens. The results further inform our understanding of the symbiotic light organ environment. IMPORTANCE By supplementing a rich yeast-based medium, we were able to recover V. fischeri mutants with insertions in conditionally essential genes, and further characterization of these mutants provided new insights into this bacterium's symbiotic environment. Most notably, we show evidence that the squid host can provide V. fischeri with enough ALA to support its growth in the light organ, paralleling the finding that legumes provide Bradyrhizobium ALA in symbiotic nodules. Taken together, our results show how a simple method of augmenting already rich media can expand the reach and utility of defined mutant libraries.

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