Frankia discariae sp. nov.: an infective and effective microsymbiont isolated from the root nodule of Discaria trinervis.

Strain BCU110501(T) was the first isolate reported to fulfill Koch's postulates by inducing effective nodules on its host plant of origin Discaria trinervis (Rhalmnaceae). Based on 16S rRNA gene sequence similarities, the strain was found to be most closely related to the type strain of Frankia elaeagni DSM 46783(T) (98.6%) followed by F. alni DSM 45986(T) (98.2%), F. casuarinae DSM 45818(T) (97.8%) and F. inefficacies DSM 45817(T) (97.8%). Digital DNA:DNA hybridizations (dDDH) between strain BCU110501(T)and the type strains of other Frankia species were clearly below the cutoff point of 70%. The G+C content of DNA is 72.36%. The cell wall of strain BCU110501(T) contained meso-diaminopimelic acid and the cell sugars were galactose, glucose, mannose, xylose and ribose. Polar lipids were phosphatidylinositol (PI), diphosphatidylglycerol (DPG), glycophospholipid (GPL1-3), phosphatidylglycerol (PG) and an unknown lipid (L). The major fatty acids of strain BCU110501(T) consisted of iso-C16:0, C17:1 w8c and C16:0. Major menaquinones were MK9 (H4), MK9 (H6) and MK9 (H2). Based on these analyses, strain BCU110501(T) (=DSM 46785(T)=CECT 9042(T)) should be classified as the type strain of a novel Frankia species, for which the name Frankia discariae sp. nov. is proposed.