Nitratireductor aquibiodomus gen. nov., sp. nov., a novel α-proteobacterium from the marine denitrification system of the Montreal Biodome (Canada)

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Abstract
The Montreal Biodome operates a methanol-fed denitrification system that treats the water in its three million litre marine mesocosm. An unknown bacterium, named strain NL21T, was isolated from this system on TSA and R2A agar. The organism is a Gram-negative, rod-shaped (1×3 μm) facultative aerobe. Optimal growth conditions on R2A agar are 30–35 °C, pH 7–7·5 and 1 % (w/w) NaCl. Phylogenetic analysis of the 16S rDNA sequence reveals that strain NL21Tforms a novel lineage in the family ‘Phyllobacteriaceae’ within theα2 subgroup of theProteobacteria. The closest related genera areAminobacter,Pseudaminobacter,MesorhizobiumandDefluvibacter. Major cellular fatty acids are C18 : 1ω7c(75 %), C19 : 0ω8ccyclopropane (9·4 %) and C18 : 0(4·2 %). The DNA G+C content of strain NL21T(57 mol%) differs from those of all other described members of the ‘Phyllobacteriaceae’ (60–64 mol%). Strain NL21Treduces nitrate to nitrite, but does not reduce nitrite to nitrogen gas. Only a few sugars and amino acids can serve as carbon sources. Strain NL21Tis able to grow without salt and tolerates up to 5 % NaCl. Phylogenetic analysis, as well as physiological and biochemical tests, showed that strain NL21Twas different from all other members of the ‘Phyllobacteriaceae’ with validly published names. Strain NL21Ttherefore represents a novel genus, for which the nameNitratireductor aquibiodomusgen. nov., sp. nov. is proposed, with the type strain NL21T(=DSM 15645T=ATCC BAA-762T).

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