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 2T18^T, 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 2T18^T formed a monophyletic clade with Chitinibacter fontanus KCTC 42982^T, C. tainanensis KACC 11706^T and C. alvei KCTC 23839^T, with sequence similarities of 98.5, 98.4 and 95.9 %, respectively. Strain 2T18^T 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 (C_16 : 1 ω6c and/or C_16 : 1 ω7c) and C_16 : 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 2T18^T and C. fontanus KCTC 42982^T were below the thresholds used for the delineation of a novel species. Based on the phylogenetic, phenotypic, chemotaxonomic and genotypic characteristics, strain 2T18^T represents a novel species of the genus Chitinibacter, for which the name Chitinibacter bivalviorum sp. nov. is proposed. The type strain is 2T18^T (=KCTC 72821^T=CCUG 74764^T).

Iodobacter limnosediminis sp. nov., isolated from Arctic lake sediment

A Gram-reaction-negative, motile, non-violet-pigmented, rod-shaped bacterial strain, designated E1T, was isolated from Arctic lake sediment. Growth occurred at 4 °C–28 °C (optimum, 18 °C), at pH 4–11(optimum, 9–10) and in the presence of 0–1 % (w/v) NaCl. The taxonomic position of E1T was analysed using a polyphasic approach. Strain E1T exhibited 16S rRNA gene sequence similarity value of 98.1 % with respect to the type strain of Iodobacter fluviatilis , but no more than 93 % with the type strains of other recognized species. A further DNA–DNA hybridization experiment was conducted, which demonstrated unambiguously that strain E1T was distinct from I. fluviatilis ATCC 33051T (51.3 % relatedness). The DNA G+C content of strain E1T was 52.3 mol%. Chemotaxonomic data [Q-8 as the monospecific respiratory quinone and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c, 56.1 %) and C16 : 0 (18.8 %) as the major cellular fatty acids] supported the affiliation of strain E1T to the genus Iodobacter . However, the results of physiological and biochemical tests allowed phenotypic differentiation of strain E1T from I. fluviatilis ATCC 33051T. On the basis of phenotypic and genotypic properties, strain E1T represents a novel species of genus Iodobacter, for which the name Iodobacter limnosediminis sp. nov. is proposed. The type strain is E1T ( = CCTCC AB 2010224T = NRRL B-59456T).

Detection of Deefgea chitinilytica in freshwater ornamental fish

AIM

To identify and characterize six chitinolytic bacterial strains isolated from ornamental fish.

METHODS AND RESULTS

Six different isolates of Deefgea chitinilytica were detected in healthy as well as diseased ornamental fish in Germany over a period of 2 years. Bacterial strains were identified using 16S rRNA partial gene sequencing and further characterized using different biochemical microtest systems and additional standard biochemical tests.

CONCLUSION

We show that commercially available biochemical microtest systems are useful for identification of D. chitinilytica, supplemented by 16S rRNA partial gene sequencing. Furthermore, this study provides new information about the occurrence of D. chitinilytica, as this is the first isolation of D. chitinilytica from animals and first described isolation in Europe.

SIGNIFICANCE AND IMPACT OF THE STUDY

Deefgea chitinilytica may be isolated regularly in fish diagnostic laboratories. Therefore, accurate identification of this bacterial species is important. Involvement of D. chitinilytica in opportunistic infections of aquatic organisms cannot be excluded and has to be further investigated.