Endobiotic bacteria colonize the tentacles of cnidaria. This paper provides first insight into the bacterial spectrum and its potential of pathogenic activities inside four cnidarian species. Sample material originating from Scottish waters comprises the jellyfish species Cyanea capillata and C. lamarckii, hydrozoa Tubularia indivisa and sea anemone Sagartia elegans. Mixed cultures of endobiotic bacteria, pure cultures selected on basis of haemolysis, but also lyophilized samples were prepared from tentacles and used for DGGE-profiling with subsequent phylogenetic analysis of 16S rDNA fragments. Bacteria were detected in each of the cnidarian species tested. Twenty-one bacterial species including four groups of closely related organisms were found in culture material. The species within these groups could not be differentiated from each other (one group of Pseudoalteromonas spp., two groups of Shewanella spp., one group of Vibrio spp.). Each of the hosts exhibits a specific endobacterial spectrum. Solely Cyanea lamarckii harboured Moritella viscosa. Only in Cyanea capillata, members of the Shewanella group #2 and the species Pseudoalteromonas arctica, Shewanella violacea, Sulfitobacter pontiacus and Arcobacter butzleri were detected. Hydrozoa Tubularia indivisa provided an amazingly wide spectrum of nine bacterial species. Exclusively, in the sea anemone Sagartia elegans, the bacterial species P. aliena was found. Overall eleven bacterial species detected were described recently as novel species. Four 16S rDNA fragments generated from lyophilized material displayed extremely low relationship to their next neighbours. These organisms are regarded as members of the endobiotic ''terra incognita''. Since the origin of cnidarian toxins is unclear, the possible pathogenic activity of endobiotic bacteria has to be taken into account. Literature data show that their next neighbours display an interesting diversity of haemolytic, septicaemic and necrotic actions including the production of cytotoxins, tetrodotoxin and R-toxin. Findings of haemolysis tests support the literature data. The potential producers are Endozoicimonas elysicola, Moritella viscosa, Photobacterium profundum, P. aliena, P. tetraodonis, Shewanella waksmanii, Vibrio splendidus, V. aestuarius, Arcobacter butzleri.

This paper provides Wrst information on organlike bacterial aggregates in the tentacles of the sea anemone Metridium senile. The specimens were collected from waters near Helgoland (German Bight, North Sea) and the Orkney Islands. Tentacles were prepared for morphological inspection by light and scanning electron microscopy as well as for the phylogenetic analysis of endocytic bacteria. Bacterial aggregates are located in caverns of the tentacles' epidermis. The aggregates are enwrapped in thin envelopes, which contain coccoid and/or rod-shaped tightly packed bacteria of diVerent division states. Most of the bacterial cells are connected by Wne Wlamentous structures. The phylogenetic determination is based on the sequence data of the 16S rDNA derived from tentacle material. Sequence analysis revealed three diVerent subgroups of intratentacular proteobacteria. The dominant band, detected in all of the samples tested, showed a close relationship (98%) to a gram-negative Endozoicimonas elysicola. Two bands, only detected in tentacles of M. senile from Helgoland were assigned to Pseudomonas saccherophilia (99%), a knallgas bacterium, and to Ralstonia pickettii (100%). The bacteria represent a speciWc bacterial community. Their DGGE proWles do not correspond to the proWles of the planktonic bacteria generated from seawater close to the habitats of the anemones. The allocation of DNA sequences to the diVerent morphotypes, their isolation, culturing and the elucidation of the physiological functions of intratentacular bacteria are in progress.

This paper provides the first information on diversity based on sequence data of the 16S rDNA of intratunical bacteria in the colonial ascidian Diplosoma migrans and its embryonic offspring. Ascidians were collected from waters near Helgoland (German Bight, North Sea). Sample material comprised tunic tissue, bacteria collected from tunic tissue, eggs with single embryos at different developmental stages, and freeswimming larvae. Bacterial 16S rDNA from D. migrans was directly amplified using PCR. DNA species were separated using denaturing gradient gel electrophoresis (DGGE). DGGE profiles generated ca. ten different distinguishable operational taxonomic units. Eleven bands from different sample materials were successfully re-amplified and sequenced. Sequence data generated five different subgroups of intratunical proteobacteria. The dominant band, detected in all of the samples tested, showed a low degree of relationship (84-86%) to Ruminococcus flavefaciens (d-subgroup). A weaker band, located above, which was not detected in all of the samples, was also similarly related to R. flavefaciens. Other bands derived from tunic material and embryonic stages showed closer relationship (ca. 97-99%) to Pseudomonas saccherophilia, a knallgas bacterium, and Ralstonia pickettii, a pathogen bacterium (both members of the b-subgroup). A solitary band generated from tunic material was assigned to a typical marine Flavobacterium symbiont (95%). Finally, a band from isolated bacteria was related (96%) to pathogen Arcobacter butzleri (e-subgroup). At this state of the investigation, a reliable interpretation of the ecological functions of intratunical bacteria cannot yet be given. This is due to the low degree of relationship of some of the bacteria and the fact that not all of the characteristic bands were successfully sequenced. However, the intratunical bacteria represent a unique bacterial community. Their DGGE profiles do not correspond to the profiles of the planktonic bacteria generated from surface seawater close to the ascidian habitat. The allocation of DNA sequences to the different morphotypes, their isolation and culturing, and the elucidation of the physiological functions of intratunical bacteria are in progress.

This is the first genetic analysis comparing cultured endobacteria discovered in the tentacles of cnidarian species (Tubularia indivisa, Tubularia larynx, Corymorpha nutans, Sagartia elegans) with those found in the cerata tips of selected nudibranch species (Berghia caerulescens, Coryphella lineata, Coryphella gracilis, Janolus cristatus, Polycera faeroensis, Polycera quadrilineata, Doto coronata, Dendronotus frondosus). Shared pathogenic activities were found among other microorganisms in the Pseudoalteromonas tetraodonis group (TTX), and the Vibrio splendidus group (haemolytic, septicaemic, necrotic activity). Specific autochthonous endobacteria of extremely low similarity to their next neighbours were detected in nudibranch cerata. These organisms are regarded as new and unknown endobacteria; among them were Pseudoalteromonas luteoviolacea (95%), Orientia tsutsugamushi (84%), Gracilimonas tropica (96%), Balneola alkaliphia (95%), Loktanella rosea (97%). SEM micrographs provide insight into endobacterial aggregates in cnidarian tentacles and nudibranch cerata. Since certain nudibranch predators prey on cnidarian species, it is assumed that cnidarian tentacle bacteria are directly transferred to nudibranch cerata. The pathogenic endobacteria may contribute to the chemical defence of both the nudibranch and cnidarian species investigated.

The SEM investigation of nudibranch cerata material exhibits endobacterial morphotypes found in 12 out of 13 species tested: Aeolidia papillosa, Berghia caerulescens, Coryphella brownii, Coryphella lineata, Coryphella verrucosa, Cuthona amoena, Facelina coronata, Flabellina pedata, Dendronotus frondosus, Doto coronata, Tritonia plebeia and Janolus cristatus. Endobacteria could not be detected inside Tritonia hombergi. Endobacterial morphology found inside nudibranch species was compared to bacterial morphotypes detected earlier in tentacles of cnidarian species. SEM micrographs show endobacterial analogy among nudibranch species, but also similarity to cnidarian endobacteria investigated earlier. Of course, morphological data of microbes do not allow their identification. However, since most of these nudibranch species prey on cnidaria, it cannot be excluded that many of the endobacteria detected inside nudibranch species may originate from their cnidarian prey. Our previous data describing genetic affiliation of endobacteria from nudibranchian and cnidarian species support this assumption. Dominant coccoid endobacteria mostly exhibit smooth surface and are tightly packed as aggregates and/or wrapped in envelopes. Such bacterial aggregate type has been described previously in tentacles of the cnidarian species Sagartia elegans. Similar coccoid bacteria, lacking envelopes were also found in other nudibranch species. A different type of coccoid bacteria, characterized by a rough surface, was detected inside cerata of the nudibranch species Berghia caerulescens, and surprisingly, inside tentacles of the cnidarian species Tubularia indivisa. In contrast to cnidarian endobacteria, rod-shaped microorganisms are largely absent in nudibranch cerata.