Chitinibacter bivalviorum sp. nov., isolated from the gut of the freshwater mussel Anodonta arcaeformis.

A novel Gram-stain-negative, aerobic, rod-shaped bacterium with a single polar flagellum, designated strain 2T18T, was isolated from the gut of the freshwater mussel Anodonta arcaeformis collected in the Republic of Korea. Phylogenetic analyses based on 16S rRNA gene sequences showed that the strain belonged to the genus Chitinibacter. Strain 2T18T formed a monophyletic clade with Chitinibacter fontanus KCTC 42982T, C. tainanensis KACC 11706T and C. alvei KCTC 23839T, with sequence similarities of 98.5, 98.4 and 95.9 %, respectively. Strain 2T18T exhibited optimal growth at 30 °C, at pH 8 and with 0.5 % (w/v) NaCl. The major isoprenoid quinone was ubiquinone-8 (Q-8). The predominant fatty acids were summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c) and C16 : 0. The polar lipids comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified lipid, three unidentified phospholipids and two unidentified aminophospholipids. The G+C content of the genomic DNA was 50.6 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between strains 2T18T and C. fontanus KCTC 42982T were below the thresholds used for the delineation of a novel species. Based on the phylogenetic, phenotypic, chemotaxonomic and genotypic characteristics, strain 2T18T represents a novel species of the genus Chitinibacter, for which the name Chitinibacter bivalviorum sp. nov. is proposed. The type strain is 2T18T (=KCTC 72821T=CCUG 74764T).

Association between environmental microbiota and indigenous bacteria found in hemolymph, extrapallial fluid and mucus of Anodonta cygnea (Linnaeus, 1758).

Bivalves filter and accumulate large numbers of microorganisms present in the harvesting water. A complete understanding of the balance between Anodonta cygnea and the microbiota present in their surrounding environment remains incomplete. Therefore, the aim of this study was to quantify and identify the indigenous bacteria in the biological fluids of A. cygnea collected from Mira Lagoon in northern Portugal. The results showed Vibrio metschnikovii and Aeromonas sobria as the dominant groups. The median for total bacteria from mucus was 3.1 × 10(3) CFU g(-1), whereas the range in means from fluids was 1.5 × 10(2) to 6.5 × 10(2) CFU ml(-1). During the experimental work, Escherichia coli and enterococci were not detected in healthy A. cygnea. However, the periodic detection of E. coli and enterococci in Mira lagoon revealed its presence in the water. Our observations suggest that A. cygnea has the ability to filter and eliminate E. coli, present in the surrounding environment, through an active phagocytic process conducted by hemolymph circulating cells, the hemocytes.