Polyphasic characterization of the genus Leptothrix: New descriptions of Leptothrix mobilis sp. nov. and Leptothrix discophora sp. nov. nom. rev. and emended description of Leptothrix cholodnii emend

Strain Feox-1 was isolated from the sediment of a big freshwater lake (Chiemsee) in Upper Bavaria, Germany. The site of isolation was characterized by dark-brown ferromanganese deposits produced by sheated bacteria belonging to the genus Leptothrix. Cells of the newly isolated strain were gram-negative, rod-shaped and highly motile by a single polar flagellum. Although sheaths were not formed strain Feox-1 could be affiliated to the genus Leptothrix by its ability to oxidize manganese at circumneutral pH values. A polyphasic approach was used to determine the taxonomic status of Feox-1 and of the other currently available Leptothrix strains which have been only partly described. Physiological tests, fatty acid analyses, DNA-DNA hybridization experiments and sequencing of 16S rRNA genes indicated that Feox-1 belongs to a new species, for which the name Leptothrix mobilis is proposed. Main characteristics of the newly proposed species are as follows: Good growth occurs in the range of 10 to 37°C and pH 6.5 to 8.5. Only very few compounds are utilized as sole carbon source. Cells contain as major fatty acids hexadecanoic acid, cis-9-hexadecenoic acid and octadecenoic acid; minor fatty acids are 3-hydroxydecanoic acid, dodecanoic acid, tetradecanoic acid and cis-9,10-methyleneoctadecanoic acid. The guanine-plus-cytosine content of the DNA is 68 mol%. Taxonomic studies of strains belonging to the non-validly described species "Leptothrix discophora" and to Leptothrix cholodnii led to the description of Leptothrix discophora sp. nov. nom. rev. and to an emended description of Leptothrix cholodnii. In addition, the two strains LMG 8142 and LMG 8143 originally assigned to "Leptothrix discophora" were transferred to Leptothrix cholodnii.