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Endozoicomonas Are Specific, Facultative Symbionts of Sea Squirts.

Schreiber L, Kjeldsen KU, Funch P, Jensen J, Obst M, López-Legentil S, Schramm A - Front Microbiol (2016)

Bottom Line: The strains tested negative for cytotoxic or antibacterial activity.Based on these observations, we propose ascidian-associated Endozoicomonas to be commensals, living off the mucus continuously secreted into the pharynx.The combined results indicate a host-specific, yet facultative symbiosis between ascidians and Endozoicomonas.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioscience, Center for Geomicrobiology and Section for Microbiology, Aarhus University Aarhus, Denmark.

ABSTRACT
Ascidians are marine filter feeders and harbor diverse microbiota that can exhibit a high degree of host-specificity. Pharyngeal samples of Scandinavian and Mediterranean ascidians were screened for consistently associated bacteria by culture-dependent and -independent approaches. Representatives of the Endozoicomonas (Gammaproteobacteria, Hahellaceae) clade were detected in the ascidian species Ascidiella aspersa, Ascidiella scabra, Botryllus schlosseri, Ciona intestinalis, Styela clava, and multiple Ascidia/Ascidiella spp. In total, Endozoicomonas was detected in more than half of all specimens screened, and in 25-100% of the specimens for each species. The retrieved Endozoicomonas 16S rRNA gene sequences formed an ascidian-specific subclade, whose members were detected by fluorescence in situ hybridization (FISH) as extracellular microcolonies in the pharynx. Two strains of the ascidian-specific Endozoicomonas subclade were isolated in pure culture and characterized. Both strains are chemoorganoheterotrophs and grow on mucin (a mucus glycoprotein). The strains tested negative for cytotoxic or antibacterial activity. Based on these observations, we propose ascidian-associated Endozoicomonas to be commensals, living off the mucus continuously secreted into the pharynx. Members of the ascidian-specific Endozoicomonas subclade were also detected in seawater from the Scandinavian sampling site, which suggests acquisition of the symbionts by horizontal transmission. The combined results indicate a host-specific, yet facultative symbiosis between ascidians and Endozoicomonas.

No MeSH data available.


Related in: MedlinePlus

Dendrogram of 16S rRNA gene sequences of Endozoicomonas affiliating with the ascidian-specific subclade depicted in Figure 1. Host species and geographic origin are given for each sequence, followed by the corresponding accession number in brackets. Sequences generated in the present study are shown in bold face. Sequences originating from Endozoicomonas isolates are marked with an asterisk. The dendrogram was truncated and does not show an additional 77 sequences of bacteria associated with Atlantic and Pacific specimens of the ascidian Ciona intestinalis (all from Dishaw et al., 2014). A summary of partial Endozoicomonas sequences generated in this study and confidently assigned to the ascidian-specific subclade was added manually (indicated with dotted lines) to illustrate host and geographic distribution. For these, the number of specimens harboring representatives of the ascidian-specific subclade as well as the total number of positively assigned sequences is shown in brackets (see also Table S6). Branch lengths do not represent phylogenetic distances.
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Figure 2: Dendrogram of 16S rRNA gene sequences of Endozoicomonas affiliating with the ascidian-specific subclade depicted in Figure 1. Host species and geographic origin are given for each sequence, followed by the corresponding accession number in brackets. Sequences generated in the present study are shown in bold face. Sequences originating from Endozoicomonas isolates are marked with an asterisk. The dendrogram was truncated and does not show an additional 77 sequences of bacteria associated with Atlantic and Pacific specimens of the ascidian Ciona intestinalis (all from Dishaw et al., 2014). A summary of partial Endozoicomonas sequences generated in this study and confidently assigned to the ascidian-specific subclade was added manually (indicated with dotted lines) to illustrate host and geographic distribution. For these, the number of specimens harboring representatives of the ascidian-specific subclade as well as the total number of positively assigned sequences is shown in brackets (see also Table S6). Branch lengths do not represent phylogenetic distances.

Mentions: Despite divergent tree topologies, several host-specific subclades were consistently detected (Figure 1; Figures S4–S6). Most relevant to this study and with the exception of one of the two sequences originating from the Mediterranean C. dellechiajei, all ascidian-derived Endozoicomonas nearly full-length sequences formed a newly defined, ascidian-specific subclade (Figures 1, 2). This subclade contained 88 ascidian-derived sequences: eight originating from Baltic Sea Ascidia and Ascidiella species (this study), one originating from a Mediterranean specimen of C. dellechiajei (Martínez-García et al., 2007) and 79 originating from Atlantic and Pacific specimens of C. intestinalis (Dishaw et al., 2014; Figure 2). Pairwise sequence identities within the subclade were as low as 96.8% (Table S5); this indicates a clade at the genus level (Yarza et al., 2014) containing different species. The most closely related species to this subclade are Endozoicomonas atrinae (isolated from the intestine of the marine pen shell Atrina pectinata) and Endozoicomonas elysicola (isolated from the marine sea slug Elysia ornata) with sequence identities to the ascidian-specific subclade of 96.6–98.1 and 96.5–98.0%, respectively (Table S5). The majority of generated partial Endozoicomonas 16S rRNA gene sequences (61%; 185 out of 301 sequences) could be confidently assigned to the ascidian-specific subclade (Figure 2; Table S6). However, for sequences obtained from B. schlosseri, the only colonial ascidian tested in the present study, overall only 11% (3 out of 28) of the retrieved Endozoicomonas sequences affiliated with the ascidian-specific subclade (Table S6). Other noteworthy cases include two specimens of Ascidia sp. (specimens AM-5 and AV-12) and two specimens of A. scabra (AA-12 and AS-3), where also the majority of Endozoicomonas sequences (>70%) did not affiliate with the ascidian-specific subclade (Table S6). This result may suggest a larger diversity of ascidian-associated Endozoicomonas (possibly divided into ascidian specialists and more generalist species), or simply be due to insufficient phylogenetic information.


Endozoicomonas Are Specific, Facultative Symbionts of Sea Squirts.

Schreiber L, Kjeldsen KU, Funch P, Jensen J, Obst M, López-Legentil S, Schramm A - Front Microbiol (2016)

Dendrogram of 16S rRNA gene sequences of Endozoicomonas affiliating with the ascidian-specific subclade depicted in Figure 1. Host species and geographic origin are given for each sequence, followed by the corresponding accession number in brackets. Sequences generated in the present study are shown in bold face. Sequences originating from Endozoicomonas isolates are marked with an asterisk. The dendrogram was truncated and does not show an additional 77 sequences of bacteria associated with Atlantic and Pacific specimens of the ascidian Ciona intestinalis (all from Dishaw et al., 2014). A summary of partial Endozoicomonas sequences generated in this study and confidently assigned to the ascidian-specific subclade was added manually (indicated with dotted lines) to illustrate host and geographic distribution. For these, the number of specimens harboring representatives of the ascidian-specific subclade as well as the total number of positively assigned sequences is shown in brackets (see also Table S6). Branch lengths do not represent phylogenetic distances.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4940369&req=5

Figure 2: Dendrogram of 16S rRNA gene sequences of Endozoicomonas affiliating with the ascidian-specific subclade depicted in Figure 1. Host species and geographic origin are given for each sequence, followed by the corresponding accession number in brackets. Sequences generated in the present study are shown in bold face. Sequences originating from Endozoicomonas isolates are marked with an asterisk. The dendrogram was truncated and does not show an additional 77 sequences of bacteria associated with Atlantic and Pacific specimens of the ascidian Ciona intestinalis (all from Dishaw et al., 2014). A summary of partial Endozoicomonas sequences generated in this study and confidently assigned to the ascidian-specific subclade was added manually (indicated with dotted lines) to illustrate host and geographic distribution. For these, the number of specimens harboring representatives of the ascidian-specific subclade as well as the total number of positively assigned sequences is shown in brackets (see also Table S6). Branch lengths do not represent phylogenetic distances.
Mentions: Despite divergent tree topologies, several host-specific subclades were consistently detected (Figure 1; Figures S4–S6). Most relevant to this study and with the exception of one of the two sequences originating from the Mediterranean C. dellechiajei, all ascidian-derived Endozoicomonas nearly full-length sequences formed a newly defined, ascidian-specific subclade (Figures 1, 2). This subclade contained 88 ascidian-derived sequences: eight originating from Baltic Sea Ascidia and Ascidiella species (this study), one originating from a Mediterranean specimen of C. dellechiajei (Martínez-García et al., 2007) and 79 originating from Atlantic and Pacific specimens of C. intestinalis (Dishaw et al., 2014; Figure 2). Pairwise sequence identities within the subclade were as low as 96.8% (Table S5); this indicates a clade at the genus level (Yarza et al., 2014) containing different species. The most closely related species to this subclade are Endozoicomonas atrinae (isolated from the intestine of the marine pen shell Atrina pectinata) and Endozoicomonas elysicola (isolated from the marine sea slug Elysia ornata) with sequence identities to the ascidian-specific subclade of 96.6–98.1 and 96.5–98.0%, respectively (Table S5). The majority of generated partial Endozoicomonas 16S rRNA gene sequences (61%; 185 out of 301 sequences) could be confidently assigned to the ascidian-specific subclade (Figure 2; Table S6). However, for sequences obtained from B. schlosseri, the only colonial ascidian tested in the present study, overall only 11% (3 out of 28) of the retrieved Endozoicomonas sequences affiliated with the ascidian-specific subclade (Table S6). Other noteworthy cases include two specimens of Ascidia sp. (specimens AM-5 and AV-12) and two specimens of A. scabra (AA-12 and AS-3), where also the majority of Endozoicomonas sequences (>70%) did not affiliate with the ascidian-specific subclade (Table S6). This result may suggest a larger diversity of ascidian-associated Endozoicomonas (possibly divided into ascidian specialists and more generalist species), or simply be due to insufficient phylogenetic information.

Bottom Line: The strains tested negative for cytotoxic or antibacterial activity.Based on these observations, we propose ascidian-associated Endozoicomonas to be commensals, living off the mucus continuously secreted into the pharynx.The combined results indicate a host-specific, yet facultative symbiosis between ascidians and Endozoicomonas.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioscience, Center for Geomicrobiology and Section for Microbiology, Aarhus University Aarhus, Denmark.

ABSTRACT
Ascidians are marine filter feeders and harbor diverse microbiota that can exhibit a high degree of host-specificity. Pharyngeal samples of Scandinavian and Mediterranean ascidians were screened for consistently associated bacteria by culture-dependent and -independent approaches. Representatives of the Endozoicomonas (Gammaproteobacteria, Hahellaceae) clade were detected in the ascidian species Ascidiella aspersa, Ascidiella scabra, Botryllus schlosseri, Ciona intestinalis, Styela clava, and multiple Ascidia/Ascidiella spp. In total, Endozoicomonas was detected in more than half of all specimens screened, and in 25-100% of the specimens for each species. The retrieved Endozoicomonas 16S rRNA gene sequences formed an ascidian-specific subclade, whose members were detected by fluorescence in situ hybridization (FISH) as extracellular microcolonies in the pharynx. Two strains of the ascidian-specific Endozoicomonas subclade were isolated in pure culture and characterized. Both strains are chemoorganoheterotrophs and grow on mucin (a mucus glycoprotein). The strains tested negative for cytotoxic or antibacterial activity. Based on these observations, we propose ascidian-associated Endozoicomonas to be commensals, living off the mucus continuously secreted into the pharynx. Members of the ascidian-specific Endozoicomonas subclade were also detected in seawater from the Scandinavian sampling site, which suggests acquisition of the symbionts by horizontal transmission. The combined results indicate a host-specific, yet facultative symbiosis between ascidians and Endozoicomonas.

No MeSH data available.


Related in: MedlinePlus