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Euichi Hirose - One of the best experts on this subject based on the ideXlab platform.
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first records of didemnid ascidians harbouring Prochloron from caribbean panama genetic relationships between caribbean and pacific photosymbionts and host ascidians
Systematics and Biodiversity, 2012Co-Authors: Euichi Hirose, Xavier Turon, Susanna Lopezlegentil, Patrick M Erwin, Mamiko HiroseAbstract:Two didemnid ascidians associating with cyanobacterial symbionts (Prochloron spp.) were firstly recorded from Caribbean Panama: Lissoclinum verrilli, which facultatively harboured Prochloron cells on the colony surface, and Diplosoma simile, which obligately harboured algal cells in the peribranchial and common cloacal cavities within the colonies. While L. verrilli sensu stricto has been exclusively recorded from the Bermudas and Caribbean islands, D. simile is widely distributed in tropical Indo-Pacific regions including oceanic islands such as Hawaii. Partial COI sequences of D. simile from the Caribbean were identical to those from the West Pacific, suggesting a high larval-dispersal ability and broad range of environmental tolerance. Molecular phylogenetics of the symbionts, based on 16S rRNA gene sequences, revealed that both ascidian species were associated with Prochloron, while a Synechocystis sp. sequence was also obtained for L. verrilli. In addition, L. verrilli and D. simile harboured differe...
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excitation energy relaxation in a symbiotic cyanobacterium Prochloron didemni occurring in coral reef ascidians and in a free living cyanobacterium prochlorothrix hollandica
Biochimica et Biophysica Acta, 2012Co-Authors: Fumiya Hamada, Euichi Hirose, Makio Yokono, Akio Murakami, Seiji AkimotoAbstract:The marine cyanobacterium Prochloron is a unique photosynthetic organism that lives in obligate symbiosis with colonial ascidians. We compared Prochloron harbored in four different host species and cultured Prochlorothrix by means of spectroscopic measurements, including time-resolved fluorescence, to investigate host-induced differences in light-harvesting strategies between the cyanobacteria. The light-harvesting efficiency of photosystems including antenna Pcb, PS II–PS I connection, and pigment status, especially that of PS I Red Chls, were different among the four samples. We also discuss relationships between these observed characteristics and the light conditions, to which Prochloron cells are exposed, influenced by distribution pattern in the host colonies, presence or absence of tunic spicules, and microenvironments within the ascidians' habitat.
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Transmission of cyanobacterial symbionts during embryogenesis in the coral reef ascidians Trididemnum nubilum and T. clinides (Didemnidae, Ascidiacea, Chordata).
The Biological Bulletin, 2012Co-Authors: Aoi Kojima, Euichi HiroseAbstract:Vertical transmission of cyanobacterial symbionts occurs in didemnid ascidians harboring Prochloron as an obligate symbiont; the photosymbionts are transferred from the parental ascidian colony to the offspring in various ways depending on host species. Although several didemnids harbor non-Prochloron cyanobacteria in their tunics, few studies have reported the processes of vertical transmission in these didemnids. Here we describe the histological processes of the transmission of cyanobacteria in two didemnids, Trididemnum nubilum harboring Synechocystis and T. clinides harboring three cyanobacterial species. In both species, the photosymbionts in the tunic of the parent colony were apparently captured by the tunic cells of the host and transferred to the embryos brooded in the tunic. The symbiont cells were then incorporated into the inner tunic of the embryo. This mode of transmission is essentially the same as that of T. miniatum harboring Prochloron in the tunic, although there are some differences a...
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Algal symbionts in the larval tunic lamellae of the colonial ascidian Lissoclinum timorense (Ascidiacea, Didemnidae).
Zoological Science, 2008Co-Authors: Euichi Hirose, Shunsuke NakabayashiAbstract:Lissoclinum timorense is a colonial ascidian that harbors the prokaryotic alga Prochloron . The algal photosymbionts adhere to the lamellae of the tunic on the posterior half of the trunk of larvae, which aggregate in the common cloacal cavity of the mother colony. Bead-adhesion tests demonstrated that the lamellae are adhesive, whereas the anterior half of the larval trunk is not. The anterior half is covered with a thin layer of outer tunic, which probably prevents Prochloron cells from attaching and interfering with sensory receptors and adhesive organs. The larval structures and the mode of algal transmission between generations are very similar to those of the Prochloron -harboring ascidian Didemnum molle . Molecular phylogenetic analyses have suggested that photosymbiosis was independently established in each genus, and thus the apparent similarity in the larvae probably resulted from convergence. The distribution pattern of photosymbionts is probably more determinative of algal transmission than phylogenetic constraints.
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host specificity and phylogeography of the prochlorophyte Prochloron sp an obligate symbiont in didemnid ascidians
Environmental Microbiology, 2007Co-Authors: Julia Munchhoff, Euichi Hirose, Tadashi Maruyama, Michio Sunairi, Brendan P Burns, Brett A NeilanAbstract:Summary Prochloron is an oxygenic photosynthetic bacterium that lives in obligate symbiosis with didemnid ascidians, such as Diplosoma spp., Lissoclinum spp. and Trididemnum spp. This study investigated the genetic diversity of the genus Prochloron by constructing a phylogenetic tree based on the 16S rRNA gene sequences of 27 isolates from 11 species of didemnid ascidians collected from Japan, Australia and the USA. The 27 isolates formed three phylogenetic groups: 22 of the samples were identified to be closely related members of Prochloron. Two samples, isolated from Trididemnum nubilum and Trididemnum clinides, were found to belong to the species Synechocystis trididemni, the closest relative of Prochloron. Three isolates formed a separate group from both Prochloron sp. and S. trididemni, potentially indicating a new symbiotic phylotype. Genomic polymorphism analysis, employing cyanobacterium-specific highly iterative palindrome 1 repeats, could not delineate the isolates further. For the Prochloron sp. isolates, the phylogenetic outcome was independent of host species and geographic origin of the sample indicating a low level of host specificity, low genetic variation within the taxon and possibly a lack of a host–symbiont relationship during reproductive dispersal. This study contributes significantly to the understanding of Prochloron diversity and phylogeny, and implications for the evolutionary relationship of prochlorophytes, cyanobacteria and chloroplasts are also discussed.
Tadashi Maruyama - One of the best experts on this subject based on the ideXlab platform.
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host specificity and phylogeography of the prochlorophyte Prochloron sp an obligate symbiont in didemnid ascidians
Environmental Microbiology, 2007Co-Authors: Julia Munchhoff, Euichi Hirose, Tadashi Maruyama, Michio Sunairi, Brendan P Burns, Brett A NeilanAbstract:Summary Prochloron is an oxygenic photosynthetic bacterium that lives in obligate symbiosis with didemnid ascidians, such as Diplosoma spp., Lissoclinum spp. and Trididemnum spp. This study investigated the genetic diversity of the genus Prochloron by constructing a phylogenetic tree based on the 16S rRNA gene sequences of 27 isolates from 11 species of didemnid ascidians collected from Japan, Australia and the USA. The 27 isolates formed three phylogenetic groups: 22 of the samples were identified to be closely related members of Prochloron. Two samples, isolated from Trididemnum nubilum and Trididemnum clinides, were found to belong to the species Synechocystis trididemni, the closest relative of Prochloron. Three isolates formed a separate group from both Prochloron sp. and S. trididemni, potentially indicating a new symbiotic phylotype. Genomic polymorphism analysis, employing cyanobacterium-specific highly iterative palindrome 1 repeats, could not delineate the isolates further. For the Prochloron sp. isolates, the phylogenetic outcome was independent of host species and geographic origin of the sample indicating a low level of host specificity, low genetic variation within the taxon and possibly a lack of a host–symbiont relationship during reproductive dispersal. This study contributes significantly to the understanding of Prochloron diversity and phylogeny, and implications for the evolutionary relationship of prochlorophytes, cyanobacteria and chloroplasts are also discussed.
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multiple origins of the ascidian Prochloron symbiosis molecular phylogeny of photosymbiotic and non symbiotic colonial ascidians inferred from 18s rdna sequences
Molecular Phylogenetics and Evolution, 2006Co-Authors: Shinichi Yokobori, Brett A Neilan, Tadashi Maruyama, Atsushi Kurabayashi, Euichi HiroseAbstract:In the tropics, certain didemnid ascidians harbor the prokaryotic photosymbiont Prochloron. To date, this photosymbiosis has been found in four didemnid genera that include non-symbiotic species. Here, we report the molecular phylogeny of symbiotic and non-symbiotic didemnids based on their 18S rDNA sequences. The data cover all four genera containing symbiotic species and one other genus comprised of only non-symbiotic species. Near-complete nucleotide sequences of 18S rDNAs were determined for four non-didemnid species and 52 didemnid samples (five genera), including 48 photosymbiotic samples collected from the Ryukyu Archipelago, the Great Barrier Reef, Hawaii, and Bali. Our phylogenetic trees indicated a monophyletic origin of the family Didemnidae, as well as each of the didemnid genera. The results strongly support the hypothesis that establishment of the ascidian-Prochloron symbiosis occurred independently in the Didemnidae lineage at least once in each of the genera that possess symbiotic species.
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ultraviolet absorption in ascidian tunic and ascidian Prochloron symbiosis
Journal of the Marine Biological Association of the United Kingdom, 2004Co-Authors: Euichi Hirose, Kaori Ohtsuka, Masaharu Ishikura, Tadashi MaruyamaAbstract:To characterize the ultraviolet (UV) light-absorbing function of the ascidian tunic, the light absorption spectrum was compared in 22 ascidian species collected from tropical and temperate waters. Non-photosymbiotic ascidians (17 species) had transparent tunics transmitting both visible and UV light, or pigmented or opaque tunics equally absorb both UV and visible light. However, a prominent absorption peak around 320 nm was exclusively found in the colonial ascidians hosting the algal symbiont Prochloron sp., and this absorption peak corresponded to absorption of UV-A (320–400 nm) and UV-B (280–320 nm). The UV-absorbing substances were extracted with methanol. They were mycosporine-like amino acids (MAAs): mycosporine-glycine, palythine, shinorine, and porphyra-334. The MAAs are thought to be synthesized by the shikimic acid pathway that does not occur in animals. Since the isolated Prochloron cells contain MAAs, the symbionts are the most possible candidates as the source of the MAAs in the tunic. In Diplosoma virens , the composition of MAAs was different between isolated Prochloron cells and colony residue from which Prochloron cells were extracted.
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molecular phylogenetic relationship between two symbiotic photo oxygenic prokaryotes Prochloron sp and synechocystis trididemni
Phycologia, 2003Co-Authors: Atsuhiro Shimada, Ralph A Lewin, Satoru Kanai, Noriko Yano, Tadashi MaruyamaAbstract:Abstract Synechocystis trididemni is a photo-oxygenic prokaryotic symbiont in some didemnid ascidians. Although the cells are pink and contain phycoerythrin, they morphologically resemble those of another symbiont of other didemnids, Prochloron didemni, which has no phycobilin pigments but has both chlorophyll a and chlorophyll b. The cytological similarities suggest that they might have evolved from a common ancestor. We examined this hypothesis by comparing nucleotide sequences in gene fragments of the 16S ribosomal RNA (16S rRNA) gene and in the large subunit of Rubisco gene (rbcL). ‘Blast’ search of GenBank showed that the most similar sequences to the 16S rRNA gene and rbcL of S. trididemni were those of Prochloron sp. The percent nucleotide and amino acid identities of the 16S rRNA genes, rbcL and the deduced Rubisco amino acid sequences between Prochloron sp. and S. trididemni were 94%, 90% and 99%, respectively. In trees based on the 16S rRNA gene and rbcL sequences, S. trididemni formed a clade w...
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photosynthesis of Prochloron as affected by environmental factors
Marine Biotechnology, 2001Co-Authors: M L Dionisiosese, Tadashi Maruyama, Shigetoh MiyachiAbstract:The effects of light intensity, pH, temperature, and UV irradiation on the photosynthetic rate of Prochloron isolated from the ascidian host Lissoclinum patella, collected from Palau, were examined. Photosynthesis increased with light intensity with saturation at 500 μmol/m2 per second. It was maximum at pH 8 to 9 but almost completely suppressed below pH 7. The optimum temperature was 35° to 40°C, but the photosynthesis was absent at ≤20°C and at 45°C. It was recovered when the symbiont was transferred from 1 hour of incubation at ≤20°C to 35°C but not when transferred from incubation at 45°C. Ultraviolet irradiation severely inhibited the photosynthesis of Prochloron in isolation but not in vivo. This protection was brought about by the tunic covering the ascidian colony, which contains UV-absorbing mycosporine-like amino acids. These results indicate that the characteristic condition of the tropical marine environment largely determines the ecological distribution of Prochloron, and the ascidian tunic protects the organism from UV radiation.
Anthony W. D. Larkum - One of the best experts on this subject based on the ideXlab platform.
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in situ metabolomic and transcriptomic profiling of the host associated cyanobacteria Prochloron and acaryochloris marina
The ISME Journal, 2018Co-Authors: Lars Behrendt, Anthony W. D. Larkum, Jeanbaptiste Raina, Adrian Lutz, Mads Albertsen, Per Halkjaernielsen, Soren J Sorensen, Michael KuhlAbstract:The tropical ascidian Lissoclinum patella hosts two enigmatic cyanobacteria: (1) the photoendosymbiont Prochloron spp., a producer of valuable bioactive compounds and (2) the chlorophyll-d containing Acaryochloris spp., residing in the near-infrared enriched underside of the animal. Despite numerous efforts, Prochloron remains uncultivable, restricting the investigation of its biochemical potential to cultivation-independent techniques. Likewise, in both cyanobacteria, universally important parameters on light-niche adaptation and in situ photosynthetic regulation are unknown. Here we used genome sequencing, transcriptomics and metabolomics to investigate the symbiotic linkage between host and photoendosymbiont and simultaneously probed the transcriptional response of Acaryochloris in situ. During high light, both cyanobacteria downregulate CO2 fixing pathways, likely a result of O2 photorespiration on the functioning of RuBisCO, and employ a variety of stress-quenching mechanisms, even under less stressful far-red light (Acaryochloris). Metabolomics reveals a distinct biochemical modulation between Prochloron and L. patella, including noon/midnight-dependent signatures of amino acids, nitrogenous waste products and primary photosynthates. Surprisingly, Prochloron constitutively expressed genes coding for patellamides, that is, cyclic peptides of great pharmaceutical value, with yet unknown ecological significance. Together these findings shed further light on far-red-driven photosynthesis in natural consortia, the interplay of Prochloron and its ascidian partner in a model chordate photosymbiosis and the uncultivability of Prochloron.
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microenvironmental ecology of the chlorophyll b containing symbiotic cyanobacterium Prochloron in the didemnid ascidian lissoclinum patella
Frontiers in Microbiology, 2012Co-Authors: Michael Kuhl, Lars Behrendt, Erik Trampe, Klaus Qvortrup, Ulrich Schreiber, Sergey M Borisov, Ingo Klimant, Anthony W. D. LarkumAbstract:The discovery of the cyanobacterium Prochloron was the first finding of a bacterial oxyphototroph with chlorophyll (Chl) b, in addition to Chl a. It was first described as Prochloron didemni but a number of clades have since been described. Prochloron is a conspicuously large (7-25 µm) unicellular cyanobacterium living in a symbiotic relationship, primarily with (sub-) tropical didemnid ascidians; it has resisted numerous cultivation attempts and appears truly obligatory symbiotic. Recently, a Prochloron draft genome was published, revealing no lack of metabolic genes that could explain the apparent inability to reproduce and sustain photosynthesis in a free-living stage. Possibly, the unsuccessful cultivation is partly due to a lack of knowledge about the microenvironmental conditions and ecophysiology of Prochloron in its natural habitat. We used microsensors, variable chlorophyll fluorescence imaging and imaging of O2 and pH to obtain a detailed insight to the microenvironmental ecology and photobiology of Prochloron in hospite in the didemnid ascidian Lissoclinum patella. The microenvironment within ascidians is characterized by steep gradients of light and chemical parameters that change rapidly with varying irradiances. The interior zone of the ascidians harboring Prochloron thus became anoxic and acidic within a few min of darkness, while the same zone exhibited O2 super-saturation and strongly alkaline pH after a few min of illumination. Photosynthesis showed lack of photoinhibition even at high irradiances equivalent to full sunlight, and photosynthesis recovered rapidly after periods of anoxia. We discuss these new insights on the ecological niche of Prochloron and possible interactions with its host and other microbes in light of its recently published genome and a recent study of the overall microbial diversity and metagenome of L. patella.
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isolation and characterisation of oxygen evolving thylakoids from the marine prokaryote Prochloron didemni
FEBS Letters, 1999Co-Authors: G Christen, G Stevens, P B Lukins, G Renger, Anthony W. D. LarkumAbstract:Abstract The present study describes the first successful attempt to isolate oxygen evolving thylakoids and thylakoid fragments from the marine prokaryote Prochloron didemni , a member of the recently discovered group of prochlorophytes. Oxygen evolving thylakoid membranes and fragments were isolated from seawater suspended cells of Prochloron didemni by passage of the cells through a Yeda press and subsequent differential centrifugation of the broken material. Three fractions were collected at 1000× g , 5000× g , and 30 000× g and identified by light microscopy as cells (and their fragments), thylakoids and membrane fragments, respectively. Pigment content, oxygen evolution rate and 77 K fluorescence spectra of these fractions were virtually identical. This finding indicates that the membrane fragments obtained are not enriched in photosystem II. The P680 + reduction kinetics of thylakoid membrane fragments were determined by monitoring flash induced absorption changes at 830 nm and analysing the time course of their decay. The multiphasic relaxation kinetics and their modification by NH 2 OH were found to be similar to those observed in cyanobacteria and plants. These findings provide an independent line of evidence for the idea of a high conservation of the basic structural and functional pattern of the water oxidising complex in all organisms that perform oxygenic photosynthesis.
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Identification of [8-vinyl]-protochlorophyllide a in phototrophic prokaryotes and algae: chemical and spectroscopic properties
Biochimica et Biophysica Acta, 1999Co-Authors: Michael Helfrich, Alfred Ross, Garry C. King, Athol G. Turner, Anthony W. D. LarkumAbstract:Abstract [8-vinyl]-Protochlorophyllide a 1 was isolated from a Prochloron sp. associated with the host ascidian, Lissoclinum patella. To obtain sufficient amounts for identification of the purified pigment, suitable extraction procedures and HPLC systems were developed. The structure was finally elucidated by UV-VIS and fluorescence spectroscopy, mass spectrometry and NMR (rotating-frame Overhauser enhancement spectroscopy). [8-vinyl]-Protochlorophyllide a was originally detected only as an intermediate in chlorophyll biosynthesis. Although its presence as a light-harvesting pigment was previously suggested in some prochlorophytes and eukaryotic algae, this is the first unequivocal demonstration of [8-vinyl]-protochlorophyllide a in an oxygenic phototroph. We also show that [8-vinyl]-protochlorophyllide a occurs in Prochloron species of four other ascidians as well as in Micromonas pusilla and Prochlorococcus marinus. The possible role of this pigment in photosynthesis is discussed.
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assessment of photosynthetic performance of Prochloron in lissoclinum patella in hospite by chlorophyll fluorescence measurements
Plant and Cell Physiology, 1997Co-Authors: Ulrich Schreiber, Peter J Ralph, Rolf Gademann, Anthony W. D. LarkumAbstract:Two new PAM fluorometers (pulse amplitude modulated) were used in an investigation of photosynthetic performance of Prochloron resident as a symbiont in the ascidian Lissoclinum patella, growing in a coral reef of Heron Island on the Great Barrier Reef. With a new DIVINGPAM in situ measurements of effective PSII quantum yield (/1F/Fm') as a function of quantum flux density (rapid light curves) were carried out in 2.5 m depth in the reef and in a seawater tank. Photosynthetic electron transport rates were measured on in hospite Prochloron both in situ and in collected material. Both light-limited and light-saturated yields were exceptionally high. Maximal yields (Fv/Fm) were ~0.83. A new TEACHING-PAM was employed for analysing dark-light induction and light-dark relaxation kinetics in collected samples with Prochloron in hospite. Considerable variability in kinetic responses was observed which was found to be at least in part due to differences in O2 concentration. It is suggested that endogenous reductants feed electrons into the intersystem transport chain, which normally is reoxidized by O2 (chlororespiration), and that in the dark, the reduction level of PSII acceptors is increased due to a decline in O2 concentration. The pattern of fluorescence responses differed markedly from those found in cyanobacteria and provides new insights into light-harvesting responses of a photosynthetic prokaryote with a membrane bound light-harvesting system, as contrasted with an extrinsic light-harvesting system.
Michael Kuhl - One of the best experts on this subject based on the ideXlab platform.
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in situ metabolomic and transcriptomic profiling of the host associated cyanobacteria Prochloron and acaryochloris marina
The ISME Journal, 2018Co-Authors: Lars Behrendt, Anthony W. D. Larkum, Jeanbaptiste Raina, Adrian Lutz, Mads Albertsen, Per Halkjaernielsen, Soren J Sorensen, Michael KuhlAbstract:The tropical ascidian Lissoclinum patella hosts two enigmatic cyanobacteria: (1) the photoendosymbiont Prochloron spp., a producer of valuable bioactive compounds and (2) the chlorophyll-d containing Acaryochloris spp., residing in the near-infrared enriched underside of the animal. Despite numerous efforts, Prochloron remains uncultivable, restricting the investigation of its biochemical potential to cultivation-independent techniques. Likewise, in both cyanobacteria, universally important parameters on light-niche adaptation and in situ photosynthetic regulation are unknown. Here we used genome sequencing, transcriptomics and metabolomics to investigate the symbiotic linkage between host and photoendosymbiont and simultaneously probed the transcriptional response of Acaryochloris in situ. During high light, both cyanobacteria downregulate CO2 fixing pathways, likely a result of O2 photorespiration on the functioning of RuBisCO, and employ a variety of stress-quenching mechanisms, even under less stressful far-red light (Acaryochloris). Metabolomics reveals a distinct biochemical modulation between Prochloron and L. patella, including noon/midnight-dependent signatures of amino acids, nitrogenous waste products and primary photosynthates. Surprisingly, Prochloron constitutively expressed genes coding for patellamides, that is, cyclic peptides of great pharmaceutical value, with yet unknown ecological significance. Together these findings shed further light on far-red-driven photosynthesis in natural consortia, the interplay of Prochloron and its ascidian partner in a model chordate photosymbiosis and the uncultivability of Prochloron.
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microenvironment and phylogenetic diversity of Prochloron inhabiting the surface of crustose didemnid ascidians
Environmental Microbiology, 2015Co-Authors: Daniel A Nielsen, Mathieu Pernice, Martin Schliep, Gaurav Sablok, Thomas C Jeffries, Michael Kuhl, Daniel Wangpraseurt, Peter J RalphAbstract:Summary The cyanobacterium Prochloron didemni is primarily found in symbiotic relationships with various marine hosts such as ascidians and sponges. Prochloron remains to be successfully cultivated outside of its host, which reflects a lack of knowledge of its unique ecophysiological requirements. We investigated the microenvironment and diversity of Prochloron inhabiting the upper, exposed surface of didemnid ascidians, providing the first insights into this microhabitat. The pH and O2 concentration in this Prochloron biofilm changes dynamically with irradiance, where photosynthetic activity measurements showed low light adaptation (Ek ∼80 ± 7 μmol photons m−2 s−1) but high light tolerance. Surface Prochloron cells exhibited a different fine structure to Prochloron cells from cloacal cavities in other ascidians, the principle difference being a central area of many vacuoles dissected by single thylakoids in the surface Prochloron. Cyanobacterial 16S rDNA pyro-sequencing of the biofilm community on four ascidians resulted in 433 operational taxonomic units (OTUs) where on average −85% (65–99%) of all sequence reads, represented by 136 OTUs, were identified as Prochloron via blast search. All of the major Prochloron-OTUs clustered into independent, highly supported phylotypes separate from sequences reported for internal Prochloron, suggesting a hitherto unexplored genetic variability among Prochloron colonizing the outer surface of didemnids.
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microenvironmental ecology of the chlorophyll b containing symbiotic cyanobacterium Prochloron in the didemnid ascidian lissoclinum patella
Frontiers in Microbiology, 2012Co-Authors: Michael Kuhl, Lars Behrendt, Erik Trampe, Klaus Qvortrup, Ulrich Schreiber, Sergey M Borisov, Ingo Klimant, Anthony W. D. LarkumAbstract:The discovery of the cyanobacterium Prochloron was the first finding of a bacterial oxyphototroph with chlorophyll (Chl) b, in addition to Chl a. It was first described as Prochloron didemni but a number of clades have since been described. Prochloron is a conspicuously large (7-25 µm) unicellular cyanobacterium living in a symbiotic relationship, primarily with (sub-) tropical didemnid ascidians; it has resisted numerous cultivation attempts and appears truly obligatory symbiotic. Recently, a Prochloron draft genome was published, revealing no lack of metabolic genes that could explain the apparent inability to reproduce and sustain photosynthesis in a free-living stage. Possibly, the unsuccessful cultivation is partly due to a lack of knowledge about the microenvironmental conditions and ecophysiology of Prochloron in its natural habitat. We used microsensors, variable chlorophyll fluorescence imaging and imaging of O2 and pH to obtain a detailed insight to the microenvironmental ecology and photobiology of Prochloron in hospite in the didemnid ascidian Lissoclinum patella. The microenvironment within ascidians is characterized by steep gradients of light and chemical parameters that change rapidly with varying irradiances. The interior zone of the ascidians harboring Prochloron thus became anoxic and acidic within a few min of darkness, while the same zone exhibited O2 super-saturation and strongly alkaline pH after a few min of illumination. Photosynthesis showed lack of photoinhibition even at high irradiances equivalent to full sunlight, and photosynthesis recovered rapidly after periods of anoxia. We discuss these new insights on the ecological niche of Prochloron and possible interactions with its host and other microbes in light of its recently published genome and a recent study of the overall microbial diversity and metagenome of L. patella.
Mamiko Hirose - One of the best experts on this subject based on the ideXlab platform.
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first records of didemnid ascidians harbouring Prochloron from caribbean panama genetic relationships between caribbean and pacific photosymbionts and host ascidians
Systematics and Biodiversity, 2012Co-Authors: Euichi Hirose, Xavier Turon, Susanna Lopezlegentil, Patrick M Erwin, Mamiko HiroseAbstract:Two didemnid ascidians associating with cyanobacterial symbionts (Prochloron spp.) were firstly recorded from Caribbean Panama: Lissoclinum verrilli, which facultatively harboured Prochloron cells on the colony surface, and Diplosoma simile, which obligately harboured algal cells in the peribranchial and common cloacal cavities within the colonies. While L. verrilli sensu stricto has been exclusively recorded from the Bermudas and Caribbean islands, D. simile is widely distributed in tropical Indo-Pacific regions including oceanic islands such as Hawaii. Partial COI sequences of D. simile from the Caribbean were identical to those from the West Pacific, suggesting a high larval-dispersal ability and broad range of environmental tolerance. Molecular phylogenetics of the symbionts, based on 16S rRNA gene sequences, revealed that both ascidian species were associated with Prochloron, while a Synechocystis sp. sequence was also obtained for L. verrilli. In addition, L. verrilli and D. simile harboured differe...
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Morphological process of vertical transmission of photosymbionts in the colonial ascidian Trididemnum miniatum Kott, 1977
Marine Biology, 2007Co-Authors: Euichi Hirose, Mamiko HiroseAbstract:In obligate symbioses between didemnid ascidians and prokaryotic algae (cyanobacteria), the larvae of the host ascidian usually possess Prochloron cells that are acquired from their mother colony. The process of vertical transmission of the photosymbionts has been histologically described in several species harboring Prochloron in the common cloacal cavity, where Prochloron cells are attached to the hairy surface of the tunic of the larvae during or just before larval spawning. Since the process has never been described in species harboring the photosymbionts in the tunic of the colony, here we describe the histological and ultrastructural process of vertical transmission in a photosymbiotic didemnid, Trididemnum miniatum. No photosymbionts were associated with gametes of the ascidian. Prochloron cells appeared in the epithelial pouch enclosing the embryo and were then incorporated in the tunic of embryos in late embryonic stages. Although Prochloron cells in the tunic of the colony were rarely associated with the host cells, some amoeboid-shaped tunic cells containing Prochloron cells were occasionally found around the epithelial pouch. Therefore, the host cell is thought to be a vehicle transporting the photosymbionts in the tunic of the colony to the tunic of the embryos. The photosymbiont cells were directly embedded in the tunic of the larval trunk. They were not contained in the host cells, as are those in the tunic of the colony. These observations revealed that the mechanism of vertical transmission in T. miniatum is very different from that in didemnids harboring Prochloron in the common cloacal cavity of the colonies, such as Trididemnum cyclops . The mechanisms of symbiont transmission are diverse even within the genus Trididemnum .
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Localization of Symbiotic Cyanobacteria in the Colonial Ascidian Trididemnum miniatum (Didemnidae, Ascidiacea)
Zoological Science, 2006Co-Authors: Euichi Hirose, Mamiko Hirose, Brett A NeilanAbstract:Trididemnum miniatum is a colonial ascidian harboring the photosymbiotic prokaryote Prochloron sp. These bacterial cells are located in the tunic of the host animal. The present study revealed, by ultrastructural analysis, that the Prochloron cells were exclusively distributed and proliferated in the tunic. They were shown to be embedded in the tunic matrix and to have no direct contact with ascidian cells. Some tunic cells of the ascidians, however, did phagocytize and digest the symbiont. Round cell masses were sometimes found in the tunic and appeared to consist of disintegrating cyanobacterial cells. The thoracic epidermis of ascidian zooids was often digitated, and the epidermal cells extended microvilli into the tunic. Since there were no Prochloron cells in the alimentary tract of the ascidian zooids, the photosymbionts would not be considered part of the typical diet of the host ascidians. Thin layer chromatography showed that the symbionts possessed both chlorophyll a and b, while a 16S rRNA gene phylogeny supported the identification of the photosymbiont of T. miniatum as Prochloron sp.