Phylogenetic diversity and cosymbiosis in the bioluminescent symbioses of "Photobacterium mandapamensis"

"Photobacterium mandapamensis" (proposed name) and Photobacterium leiognathi are closely related, phenotypically similar marine bacteria that form bioluminescent symbioses with marine animals. Despite their similarity, however, these bacteria can be distinguished phylogenetically by sequence divergence of their luminescence genes, luxCDAB(F)E, by the presence (P. mandapamensis) or the absence (P. leiognathi) of luxF and, as shown here, by the sequence divergence of genes involved in the synthesis of riboflavin, ribBHA. To gain insight into the possibility that P. mandapamensis and P. leiognathi are ecologically distinct, we used these phylogenetic criteria to determine the incidence of P. mandapamensis as a bioluminescent symbiont of marine animals. Five fish species, Acropoma japonicum (Perciformes, Acropomatidae), Photopectoralis panayensis and Photopectoralis bindus (Perciformes, Leiognathidae), Siphamia versicolor (Perciformes, Apogonidae), and Gadella jordani (Gadiformes, Moridae), were found to harbor P. mandapamensis in their light organs. Specimens of A. japonicus, P. panayensis, and P. bindus harbored P. mandapamensis and P. leiognathi together as cosymbionts of the same light organ. Regardless of cosymbiosis, P. mandapamensis was the predominant symbiont of A. japonicum, and it was the apparently exclusive symbiont of S. versicolor and G. jordani. In contrast, P. leiognathi was found to be the predominant symbiont of P. panayensis and P. bindus, and it appears to be the exclusive symbiont of other leiognathid fishes and a loliginid squid. A phylogenetic test for cospeciation revealed no evidence of codivergence between P. mandapamensis and its host fishes, indicating that coevolution apparently is not the basis for this bacterium's host preferences. These results, which are the first report of bacterial cosymbiosis in fish light organs and the first demonstration that P. leiognathi is not the exclusive light organ symbiont of leiognathid fishes, demonstrate that the host species ranges of P. mandapamensis and P. leiognathi are substantially distinct. The host range difference underscores possible differences in the environmental distributions and physiologies of these two bacterial species.     

Phylogenetic analysis of the <Emphasis Type="Italic">lux</Emphasis> operon distinguishes two evolutionarily distinct clades of <Emphasis Type="Italic">Photobacterium leiognathi</Emphasis>

The luminous marine bacterium Photobacterium mandapamensis was synonymized several years ago with Photobacterium leiognathi based on a high degree of phenotypic and genetic similarity. To test the possibility that P. leiognathi as now formulated, however, actually contains two distinct bacterial groups reflecting the earlier identification of P. mandapamensis and P. leiognathi as separate species, we compared P. leiognathi strains isolated from light-organ symbiosis with leiognathid fishes (i.e., ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1) with strains from seawater originally described as P. mandapamensis and later synonymized as P. leiognathi (i.e., ATCC 27561^T and ATCC 33981) and certain strains initially identified as P. leiognathi (i.e., PL-721, PL-741, 554). Analysis of the 16S rRNA and gyrB genes did not resolve distinct clades, affirming a close relationship among these strains. However, strains ATCC 27561^T, ATCC 33981, PL-721, PL-741 and 554 were found to bear a luxF gene in the lux operon (luxABFE), whereas ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1 lack this gene (luxABE). Phylogenetic analysis of the luxAB(F)E region confirmed this distinction. Furthermore, ATCC 27561^T, ATCC 33981, PL-721, PL-741 and 554 all produced a higher level of luminescence on high-salt medium, as previously described for PL-721, whereas ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1 all produced a higher level of luminescence on low-salt medium, a characteristic of P. leiognathi from leiognathid fish light organs. These results demonstrate that P. leiognathi contains two evolutionarily and phenotypically distinct clades, P. leiognathi subsp. leiognathi (strains ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1), and P. leiognathi subsp. mandapamensis (strains ATCC 27561^T, ATCC 33981, PL-721, PL-741 and 554).Electronic Supplementary Material Supplementary material is available for this article at .     

Diversification of Two Lineages of Symbiotic Photobacterium

Understanding of processes driving bacterial speciation requires examination of closely related, recently diversified lineages. To gain an insight into diversification of bacteria, we conducted comparative genomic analysis of two lineages of bioluminescent symbionts, Photobacterium leiognathi and ‘P. mandapamensis’. The two lineages are evolutionary and ecologically closely related. Based on the methods used in bacterial taxonomy for classification of new species (DNA-DNA hybridization and ANI), genetic relatedness of the two lineages is at a cut-off point for species delineation. In this study, we obtained the whole genome sequence of a representative P. leiognathi strain lrivu.4.1, and compared it to the whole genome sequence of ‘P. mandapamensis’ svers.1.1. Results of the comparative genomic analysis suggest that P. leiognathi has a more plastic genome and acquired genes horizontally more frequently than ‘P. mandapamensis’. We predict that different rates of recombination and gene acquisition contributed to diversification of the two lineages. Analysis of lineage-specific sequences in 25 strains of P. leiognathi and ‘P. mandapamensis’ found no evidence that bioluminescent symbioses with specific host animals have played a role in diversification of the two lineages.     

Genomic polymorphism in symbiotic populations of Photobacterium leiognathi

Photobacterium leiognathi forms a bioluminescent symbiosis with leiognathid fishes, colonizing the internal light organ of the fish and providing its host with light used in bioluminescence displays. Strains symbiotic with different species of the fish exhibit substantial phenotypic differences in symbiosis and in culture, including differences in 2-D PAGE protein patterns and profiles of indigenous plasmids. To determine if such differences might reflect a genetically based symbiont-strain/host-species specificity, we profiled the genomes of P. leiognathi strains from leiognathid fishes using PFGE. Individual strains from 10 species of leiognathid fishes exhibited substantial genomic polymorphism, with no obvious similarity among strains; these strains were nonetheless identified as P. leiognathi by 16S rDNA sequence analysis. Profiling of multiple strains from individual host specimens revealed an oligoclonal structure to the symbiont populations; typically one or two genomotypes dominated each population. However, analysis of multiple strains from multiple specimens of the same host species, to determine if the same strain types consistently colonize a host species, demonstrated substantial heterogeneity, with the same genomotype only rarely observed among the symbiont populations of different specimens of the same host species. Colonization of the leiognathid light organ to initiate the symbiosis therefore is likely to be oliogoclonal, and specificity of the P. leiognathi/leiognathid fish symbiosis apparently is maintained at the bacterial species level rather than at the level of individual, genomotypically defined strain types.     

Developmental and Microbiological Analysis of the Inception of Bioluminescent Symbiosis in the Marine Fish Nuchequula nuchalis (Perciformes: Leiognathidae)

Many marine fish harbor luminous bacteria as bioluminescent symbionts. Despite the diversity, abundance, and ecological importance of these fish and their apparent dependence on luminous bacteria for survival and reproduction, little is known about developmental and microbiological events surrounding the inception of their symbioses. To gain insight on these issues, we examined wild-caught larvae of the leiognathid fish Nuchequula nuchalis, a species that harbors Photobacterium leiognathi as its symbiont, for the presence, developmental state, and microbiological status of the fish's internal, supraesophageal light organ. Nascent light organs were evident in the smallest specimens obtained, flexion larvae of 6.0 to 6.5 mm in notochord length (NL), a developmental stage at which the stomach had not yet differentiated and the nascent gasbladder had not established an interface with the light organ. Light organs of certain of the specimens in this size range apparently lacked bacteria, whereas light organs of other specimens of 6.5 mm in NL and of all larger specimens harbored large populations of bacteria, representatives of which were identified as P. leiognathi. Bacteria identified as Vibrio harveyi were also present in the light organ of one larval specimen. Light organ populations were composed typically of two or three genetically distinct strain types of P. leiognathi, similar to the situation in adult fish, and the same strain type was only rarely found in light organs of different larval, juvenile, or adult specimens. Light organs of larvae carried a smaller proportion of strains merodiploid for the lux-rib operon, 79 of 249 strains, than those of adults (75 of 91 strains). These results indicate that light organs of N. nuchalis flexion and postflexion larvae of 6.0 to 6.7 mm in NL are at an early stage of development and that inception of the symbiosis apparently occurs in flexion larvae of 6.0 to 6.5 mm in NL. Ontogeny of the light organ therefore apparently precedes acquisition of the symbiotic bacteria. Furthermore, bacterial populations in larval light organs near inception of the symbiosis are genetically diverse, like those of adult fish.     

The specificity of symbiosis: Pony fish and luminescent bacteria

Luminescent bacteria isolated from light organs of seven different species (3 genera) of fishes of the family Leiognathidae were subjected to taxonomic analysis. Of the 733 isolated all but seven were identified as Photobacterium leiognathi; the others are considered to be either chance contaminants of the sampling procedure or transients within the organ. In most fish, the luminous organ appeared to contain a single predominating strain of P. leiognathi with small numbers of one to three other strains of the same species, differing by only one or two characters.     

Influence of “protective” symbionts throughout the different steps of an aphid–parasitoid interaction

Microbial associates are widespread in insects, some conferring a protection to their hosts against natural enemies like parasitoids. These protective symbionts may affect the infection success of the parasitoid by modifying behavioral defenses of their hosts, the development success of the parasitoid by conferring a resistance against it or by altering life-history traits of the emerging parasitoids. Here, we assessed the effects of different protective bacterial symbionts on the entire sequence of the host-parasitoid interaction (i.e., from parasitoid attack to offspring emergence) between the pea aphid, Acyrthosiphon pisum, and its main parasitoid, Aphidius ervi and their impacts on the life-history traits of the emerging parasitoids. To test whether symbiont-mediated phenotypes were general or specific to particular aphid–symbiont associations, we considered several aphid lineages, each harboring a different strain of either Hamiltonella defensa or Regiella insecticola, two protective symbionts commonly found in aphids. We found that symbiont species and strains had a weak effect on the ability of aphids to defend themselves against the parasitic wasps during the attack and a strong effect on aphid resistance against parasitoid development. While parasitism resistance was mainly determined by symbionts, their effects on host defensive behaviors varied largely from one aphid–symbiont association to another. Also, the symbiotic status of the aphid individuals had no impact on the attack rate of the parasitic wasps, the parasitoid emergence rate from parasitized aphids nor the life-history traits of the emerging parasitoids. Overall, no correlations between symbiont effects on the different stages of the host–parasitoid interaction was observed, suggesting no trade-offs or positive associations between symbiont-mediated phenotypes. Our study highlights the need to consider various sequences of the host-parasitoid interaction to better assess the outcomes of protective symbioses and understand the ecological and evolutionary dynamics of insect–symbiont associations.     

Evidence for the Biosynthesis of Bryostatins by the Bacterial Symbiont “Candidatus Endobugula sertula” of the Bryozoan Bugula neritina

The marine bryozoan, Bugula neritina, is the source of the bryostatins, a family of macrocyclic lactones with anticancer activity. Bryostatins have long been suspected to be bacterial products. B. neritina harbors the uncultivated gamma proteobacterial symbiont “Candidatus Endobugula sertula.” In this work several lines of evidence are presented that show that the symbiont is the most likely source of bryostatins. Bryostatins are complex polyketides similar to bacterial secondary metabolites synthesized by modular type I polyketide synthases (PKS-I). PKS-I gene fragments were cloned from DNA extracted from the B. neritina-“E. sertula” association, and then primers specific to one of these clones, KSa, were shown to amplify the KSa gene specifically and universally from total B. neritina DNA. In addition, a KSa RNA probe was shown to bind specifically to the symbiotic bacteria located in the pallial sinus of the larvae of B. neritina and not to B. neritina cells or to other bacteria. Finally, B. neritina colonies grown in the laboratory were treated with antibiotics to reduce the numbers of bacterial symbionts. Decreased symbiont levels resulted in the reduction of the KSa signal as well as the bryostatin content. These data provide evidence that the symbiont E. sertula has the genetic potential to make bryostatins and is necessary in full complement for the host bryozoan to produce normal levels of bryostatins. This study demonstrates that it may be possible to clone bryostatin genes from B. neritina directly and use these to produce bryostatins in heterologous host bacteria.     

Physiological Characteristics Underlying the Distribution Patterns of Luminous Bacteria in the Mediterranean Sea and the Gulf of Elat

Physiological characteristics of luminous bacteria isolated from the Mediterranean and Gulf of Elat were compared to determine their relationship to the specific seasonal and geographic distribution patterns of these bacteria. The effects of temperature on growth rate and yield, relative sensitivity to photooxidation, resistance to high salt concentration (8%), and ability to grow in nutrient-poor conditions appear to control these patterns. The winter appearance of Photobacterium fischeri and the succession of winter and summer types of Beneckea harveyi in the eastern Mediterranean are explained by different temperature requirements for growth. Sensitivity to photooxidation explains the disappearance of P. leiognathi, present in the main body of the Gulf of Elat throughout the year, from the shallow coastal strip. B. harveyi is present in this coastal strip which is higher in nutrients and in productivity than the open waters. Competition experiments between B. harveyi and P. leiognathi in batch and continuous culture indicate that the oligotrophic P. leiognathi is outcompeted by B. harveyi in rich and even in relatively poor media. The distribution pattern found in the Bardawil hypersaline lagoon is explained by selection of salinity-resistant mutants of B. harveyi from the Mediterranean Sea.     

Osmotic control of luminescence and growth in Photobacterium leiognathi from ponyfish light organs

Osmolarity was found to control the luminescence and growth of Photobacterium leiognathi strain LN-1a isolated from the light organ of the ponyfish Leiognathus nuchalis (family Leiognathidae). Low osmolarity (ca. 400 mOsm) stimulated luminescence per cell 80 to 100-fold to a level (ca. 2.0×10⁴ quanta·s^-1·cell^-1) equal to that of bacteria taken directly from the light organ and increased the level of luciferase per cell 8 to 10-fold compared to high osmolarity (ca. 800 mOsm). Conversely, high osmolarity stimulated oxygen uptake and growth rate 2 to 4-fold compared to low osmolarity. Of 21 additional tested strains of P. leiognathi from light organs of 9 other ponyfish species, all responded similarly. Low osmolarity may be a host control factor that functions to stimulate the luminescence and restrict the growth of ponyfish light organ bacteria in situ.     

“Candidatus Endobugula glebosa,” a Specific Bacterial Symbiont of the Marine Bryozoan Bugula simplex

The bryozoans Bugula neritina and Bugula simplex harbor bacteria in the pallial sinuses of their larvae as seen by electron microscopy. In B. neritina, the bacterial symbiont has been characterized as a gamma-proteobacterium, “Candidatus Endobugula sertula.” “Candidatus E. sertula” has been implicated as the source of the bryostatins, polyketides that provide chemical defense to the host and are also being tested for use in human cancer treatments. In this study, the bacterial symbiont in B. simplex larvae was identified by 16S rRNA-targeted PCR and sequencing as a gamma-proteobacterium closely related to and forming a monophyletic group with “Candidatus E. sertula.” In a fluorescence in situ hybridization, a 16S ribosomal DNA probe specific to the B. simplex symbiont hybridized to long rod-shaped bacteria in the pallial sinus of a B. simplex larva. The taxonomic status “Candidatus Endobugula glebosa” is proposed for the B. simplex larval symbiont. Degenerate polyketide synthase (PKS) primers amplified a gene fragment from B. simplex that closely matched a PKS gene fragment from the bryostatin PKS cluster. PCR surveys show that the symbiont and this PKS gene fragment are consistently and uniquely associated with B. simplex. Bryostatin activity assays and chemical analyses of B. simplex extracts reveal the presence of compounds similar to bryostatins. Taken together, these findings demonstrate a symbiosis in B. simplex that is similar and evolutionarily related to that in B. neritina.     

Heterogeneity of the populations of marine luminescent bacteria Photobacterium leiognathi under different conditions of cultivation

Manifestation of pleiotropic effects in the isogenic variants of the luminescent bacterium Photobacterium leiognathi 54 was investigated. The decrease or increase of the expression level of bioluminescence was caused by changes in lux operon regulation. The dynamics of the bioluminescence of dark and dim variants did not differ from the dynamics of the initial luminescent variant, but dependence of the level of luminescence intensity on the exogenous autoinducer of the lux operon was revealed. The investigated variants of P. leiognathi 54 inherited fairly stable morphological characteristics, colony architectonics, level of luminescence, and activity of some enzymes; variants with reduced bioluminescence formed colonies of the S type. Stable bright variants with S-and R-type colonies appeared both in the initial strain population and in the dark variant population, but with smaller frequency. Populations of the bright variant with R-type colonies were most heterogeneous; this can be determined by the lack of glucose repression of the bioluminescence in contrast to other investigated inherited variants of P. leiognathi.     

LuxG is a functioning flavin reductase for bacterial luminescence

The luxG gene is part of the lux operon of marine luminous bacteria. luxG has been proposed to be a flavin reductase that supplies reduced flavin mononucleotide (FMN) for bacterial luminescence. However, this role has never been established because the gene product has not been successfully expressed and characterized. In this study, luxG from Photobacterium leiognathi TH1 was cloned and expressed in Escherichia coli in both native and C-terminal His₆-tagged forms. Sequence analysis indicates that the protein consists of 237 amino acids, corresponding to a subunit molecular mass of 26.3 kDa. Both expressed forms of LuxG were purified to homogeneity, and their biochemical properties were characterized. Purified LuxG is homodimeric and has no bound prosthetic group. The enzyme can catalyze oxidation of NADH in the presence of free flavin, indicating that it can function as a flavin reductase in luminous bacteria. NADPH can also be used as a reducing substrate for the LuxG reaction, but with much less efficiency than NADH. With NADH and FMN as substrates, a Lineweaver-Burk plot revealed a series of convergent lines characteristic of a ternary-complex kinetic model. From steady-state kinetics data at 4°C pH 8.0, K_m for NADH, K_m for FMN, and k_cat were calculated to be 15.1 μM, 2.7 μM, and 1.7 s⁻¹, respectively. Coupled assays between LuxG and luciferases from P. leiognathi TH1 and Vibrio campbellii also showed that LuxG could supply FMNH⁻ for light emission in vitro. A luxG gene knockout mutant of P. leiognathi TH1 exhibited a much dimmer luminescent phenotype compared to the native P. leiognathi TH1, implying that LuxG is the most significant source of FMNH⁻ for the luminescence reaction in vivo.     

Quality or quantity: is nutrient transfer driven more by symbiont identity and productivity than by symbiont abundance?

By forming symbiotic interactions with microbes, many animals and plants gain access to the products of novel metabolic pathways. We investigated the transfer of symbiont-derived carbon and nitrogen to the sponges Aplysina cauliformis, Aplysina fulva, Chondrilla caribensis, Neopetrosia subtriangularis and Xestospongia bocatorensis, all of which host abundant microbial populations, and Niphates erecta, which hosts a sparse symbiont community. We incubated sponges in light and dark bottles containing seawater spiked with ¹³C- and ¹⁵N-enriched inorganic compounds and then measured ¹³C and ¹⁵N enrichment in the microbial (nutrient assimilation) and sponge (nutrient transfer) fractions. Surprisingly, although most sponges hosting abundant microbial communities were more enriched in ¹³C than N. erecta, only N. subtriangularis was more enriched in ¹⁵N than N. erecta. Although photosymbiont abundance varied substantially across species, ¹³C and ¹⁵N enrichment was not significantly correlated with photosymbiont abundance. Enrichment was significantly correlated with the ratio of gross productivity to respiration (P:R), which varied across host species and symbiont phylotype. Because irradiance impacts P:R ratios, we also incubated A. cauliformis in ¹³C-enriched seawater under different irradiances to determine whether symbiont carbon fixation and transfer are dependent on irradiance. Carbon fixation and transfer to the sponge host occurred in all treatments, but was greatest at higher irradiances and was significantly correlated with P:R ratios. Taken together, these results demonstrate that nutrient transfer from microbial symbionts to host sponges is influenced more by host–symbiont identities and P:R ratios than by symbiont abundance.     

LuxA gene of light organ symbionts of the bioluminescent fish Acropoma japonicum (Acropomatidae) and Siphamia versicolor (Apogonidae) forms a lineage closely related to that of Photobacterium leiognathi ssp. mandapamensis

A molecular phylogenetic analysis of luxA gene sequences of light organ symbionts of the fish Acropoma japonicum (Acropomatidae) and Siphamia versicolor (Apogonidae) revealed that the sequences were related to those of Photobacterium leiognathi ssp. mandapamensis, which is not known to occur as a light organ symbiont among bioluminescent P. leiognathi clades. The presence of another lux gene element, luxF, coding for nonfluorescent protein, provided additional support for the identity of the light organ symbionts of the fish. Cladogenesis of the light organ symbiont P. leiognathi may be influenced by the radiation of host fishes.     

Prevalence of microsporidian infection in commercially caught pink shrimp,Pandalus jordani

Pink shrimp (Pandalus jordani), a commercially harvested species in Oreegon, Washington, and California, hosts four species of microsporidian parasites: Thelohania butleri, Pleistophora crangoni, and two undescribed species placed in the collective group, Microsporidium. All parasitize the skeletal musculature giving shrimp a whitish, opaque appearance. The prevalence of microsporidian infectionin P. jordani was studied over a 6-year period (1975–1980) and was found to be very low. Of the 207, 942 shrimp exmined, 0.19% were infected with one of the four species. No substantial differences in prevalence were observed between different sampling areas in Oregon and Washington or during the years sampled. The four species occurred in each sampling area in about the same portion. T. butleri was predominant and accounted for 78.7% of all infections. Heavy exploitation of host shrimp is suggested as a possible explanation for the low microsporidian infection rates in the P. jordani population.     

Genomic and Phylogenetic Characterization of Luminous Bacteria Symbiotic with the Deep-Sea Fish Chlorophthalmus albatrossis (Aulopiformes: Chlorophthalmidae)

Bacteria forming light-organ symbiosis with deep-sea chlorophthalmid fishes (Aulopiformes: Chlorophthalmidae) are considered to belong to the species Photobacterium phosphoreum. The identification of these bacteria as P. phosphoreum, however, was based exclusively on phenotypic traits, which may not discriminate between phenetically similar but evolutionarily distinct luminous bacteria. Therefore, to test the species identification of chlorophthalmid symbionts, we carried out a genomotypic (repetitive element palindromic PCR genomic profiling) and phylogenetic analysis on strains isolated from the perirectal light organ of Chlorophthalmus albatrossis. Sequence analysis of the 16S rRNA gene of 10 strains from 5 fish specimens placed these bacteria in a cluster related to but phylogenetically distinct from the type strain of P. phosphoreum, ATCC 11040^T, and the type strain of Photobacterium iliopiscarium, ATCC 51760^T. Analysis of gyrB resolved the C. albatrossis strains as a strongly supported clade distinct from P. phosphoreum and P. iliopiscarium. Genomic profiling of 109 strains from the 5 C. albatrossis specimens revealed a high level of similarity among strains but allowed identification of genomotypically different types from each fish. Representatives of each type were then analyzed phylogenetically, using sequence of the luxABFE genes. As with gyrB, analysis of luxABFE resolved the C. albatrossis strains as a robustly supported clade distinct from P. phosphoreum. Furthermore, other strains of luminous bacteria reported as P. phosphoreum, i.e., NCIMB 844, from the skin of Merluccius capensis (Merlucciidae), NZ-11D, from the light organ of Nezumia aequalis (Macrouridae), and pjapo.1.1, from the light organ of Physiculus japonicus (Moridae), grouped phylogenetically by gyrB and luxABFE with the C. albatrossis strains, not with ATCC 11040^T. These results demonstrate that luminous bacteria symbiotic with C. albatrossis, together with certain other strains of luminous bacteria, form a clade, designated the kishitanii clade, that is related to but evolutionarily distinct from P. phosphoreum. Members of the kishitanii clade may constitute the major or sole bioluminescent symbiont of several families of deep-sea luminous fishes.     

Seasonal and Geographic Distribution of Luminous Bacteria in the Eastern Mediterranean Sea and the Gulf of Elat

Luminous bacteria in the Mediterranean Sea and the Gulf of Aqaba-Elat have different distribution patterns. In the Mediterranean Sea, Beneckea harveyi is present all year round, with different subtypes alternating in summer and winter; Photobacterium fischeri was only present during the winter. In the Gulf of Elat, P. leiognathi is present throughout the water column in similar densities during the entire year. This constancy in distribution is presumably due to the near-constancy in water temperature. In summer, Photobacterium leiognathi is replaced by B. harveyi in coastal surface waters. In the hypersaline Bardawil lagoon, only B. harveyi types are present. P. fischeri, a major component of the Mediterranean Sea winter communities, is absent from the lagoon. Luminous Beneckea strains show a great diversity in properties, e.g. temperature range for growth, sensitivity to infection by phages, sensitivity to attack by Bdellovibrio strains, and differences in tolerance to high-salinity shock. Therefore, subdivision of the taxonomic cluster of B. harveyi into subtypes is indicated. The composition of the luminous bacteria communities may serve as indicators of different marine water bodies. The symbiotic luminous bacteria of the light organ of the common Gulf of Elat fish, Photoblepharon palbebratus steinitzi, is different from any of the types described.     

Quantitative criteria for estimating the effectiveness of bioluminescence expression in natural and transgenic luminescent bacteria

Computational coefficients for estimating the effectiveness of bioluminescence expression in natural luminescent bacteria Photobacterium leiognathi 54 and transgenic strain E. coli Z905/pPHL7 bearing lux-operon in a multicopy plasmid are suggested and their use at molecular, cell, and population levels was considered. It was shown that at the population level, all transgenic variants have an advantage over natural variants of P. leiognathi 54 irrespective of the type of lux-operon regulation. At the cell level, the effectiveness of bioluminescence expression in the bright and dim variants of the transgenic strain increased by several orders. At the level of one lux-operon, the effectiveness of expression in the bright variant of the transgenic strain is substantially higher than in the natural bright variant; in dim variants, the efficiency values are similar; the effectiveness of bioluminescence expression in the dark variant of E. coli Z905-2/pPHL7 is by two orders of magnitude lower than in the dark variant of P. leiognathi 54.     

Genome sequence of Photobacterium mandapamensis strain svers.1.1, the bioluminescent symbiont of the cardinal fish Siphamia versicolor

Photobacterium mandapamensis is one of three luminous Photobacterium species able to form species-specific bioluminescent symbioses with marine fishes. Here, we present the draft genome sequence of P. mandapamensis strain svers.1.1, the bioluminescent symbiont of the cardinal fish Siphamia versicolor, the first genome of a symbiotic, luminous Photobacterium species to be sequenced. Analysis of the sequence provides insight into differences between P. mandapamensis and other luminous and symbiotic bacteria in genes involved in quorum-sensing regulation of light production and establishment of symbiosis.