Frankia colletiae sp. nov., a nitrogen-fixing actinobacterium isolated from Colletia cruciata

Abstract

A nitrogen-fixing actinobacterium strain (Cc1.17T) isolated from a root nodule of Colletia cruciata was subjected to polyphasic taxonomic studies. The strain was characterized by the presence of meso-diaminopimelic acid in its peptidoglycan, galactose, glucose, mannose, rhamnose, ribose and xylose as cell-wall sugars, phosphatidylinositol, diphosphatidylglycerol, glycophospholipids, phosphatidylglycerol, glycophospholipid and uncharacterized lipids as its polar lipids, and C16 : 0, iso-C16 : 0, C17 : 1 ω9 and C18 : 1 ω9 as major fatty acids (>10 %). Strain Cc1.17T showed 16S rRNA gene sequence similarities of 97.4–99.8 % to validly named Frankia species. Phylogenetic trees based on 16S rRNA gene and genome sequences placed strain Cc1.17T in a new lineage within the genus Frankia . Digital DNA–DNA hybridization and average nucleotide identity values between strain Cc1.17T and its closest phylogenomic neighbours were well below the thresholds recommended for prokaryotic species delineation. Therefore, strain Cc1.17T (=DSM 43829T=CECT 9313T) merits recognition as the type strain of a new species for which the name Frankia colletiae sp. nov. is proposed.