No abstract

A Gram-negative, aerobic, polar-flagellated and rod-shaped, sometimes slightly curved bacterium, designated MA5T, was isolated from the gut of an abalone of the species Haliotis gigantea collected in Japan. Phylogenetic analyses based on 16S rRNA, gyrB, hsp60 and rpoB gene sequences placed strain MA5T in the genus Arcobacter in an independent phylogenetic line. Comparison of the 16S rRNA gene sequence of this strain with those of the type strains of the established Arcobacter species revealed A. nitrofigilis (95.1 %) as nearest neighbour. Strain MA5T grew optimally at 25 °C, pH 6.0 to 9.0 and in the presence of 2 to 5 % (w/v) NaCl under both aerobic and microaerobic conditions. The predominant fatty acids found were summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c), C12 : 0 3-OH and C18 : 1 ω7c. Menaquinone-6 (MK-6) and menaquinone-7 (MK-7) were found as the major respiratory quinones. The major polar lipids detected were phosphatidylethanolamine and phosphatidylglycerol. Strain MA5T could be differentiated phenotypically from the phylogenetic closest Arcobacter species by its ability to grow on 0.05 % safranin and 0.01 % 2,3,5-triphenyl tetrazolium chloride (TTC), but not on 0.5 % NaCl. The obtained DNA G+C content of strain MA5T was 27.9 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic distinctiveness of MA5T, this strain is considered to represent a novel species of the genus Arcobacter, for which the name Arcobacter haliotis sp. nov. is proposed. The type strain is MA5T (=LMG 28652T=JCM 31147T).

Formosa haliotis sp. nov., a brown-alga-degrading bacterium isolated from the gut of the abalone Haliotis gigantea

Formosa haliotis is a brown alga-degrading bacterium isolated from the gut of abalone Haliotis gigantea. Here, we report the draft genome sequence of this bacterium and pointed out possible important features related to alginate degradation.

Gills are important organs for aquatic invertebrates because they harbor chemosynthetic bacteria, which fix inorganic carbon and/or nitrogen and provide their hosts with organic compounds. Nevertheless, in contrast to the intensive researches related to the gut microbiota, much is still needed to further understand the microbiota within the gills of invertebrates. Using abalones as a model, we investigated the community structure of microbes associated with the gills of these invertebrates using next-generation sequencing. Molecular identification of representative bacterial sequences was performed using cloning, nested PCR and fluorescence in situ hybridization (FISH) analysis with specific primers or probes. We examined three abalone species, namely Haliotis gigantea, H. discus and H. diversicolor using seawater and stones as controls. Microbiome analysis suggested that the gills of all three abalones had the unclassified Spirochaetaceae (one OTU, 15.7 ± 0.04%) and Mycoplasma sp. (one OTU, 9.1 ± 0.03%) as the core microbes. In most libraries from the gills of H. gigantea, however, a previously unknown epsilonproteobacterium species (one OTU) was considered as the dominant bacterium, which accounted for 62.2% of the relative abundance. The epsilonproteobacterium was only detected in the gills of H. diversicolor at 0.2% and not in H. discus suggesting that it may be unique to H. gigantea. Phylogenetic analysis performed using a near full-length 16S rRNA gene placed the uncultured epsilonproteobacterium species at the root of the family Helicobacteraceae. Interestingly, the uncultured epsilonproteobacterium was commonly detected from gill tissue rather than from the gut and foot tissues using a nested PCR assay with uncultured epsilonproteobacterium-specific primers. FISH analysis with the uncultured epsilonproteobacterium-specific probe revealed that probe-reactive cells in H. gigantea had a coccus-like morphology and formed microcolonies on gill tissue. This is the first report to show that epsilonproteobacterium has the potential to be a dominant species in the gills of the coastal gastropod, H. gigantea.