Abstract

Strain ARgP5(T), an actinobacterium isolated from a root nodule present on an Alnus incana subspecies rugosa shrub growing in Quebec City, Canada, was the subject of polyphasic taxonomic studies to clarify its status within the genus Frankia. 16S rRNA gene sequence similarities and ANI values between ARgP5(T) and type strains of species of the genus Frankia with validly published names were 98.8 and 82% or less, respectively. The in silico DNA G+C content was 72.4 mol%. ARgP5(T) is characterised by the presence of meso-A(2)pm, galactose, glucose, mannose, rhamnose (trace), ribose and xylose as whole-organism hydrolysates; MK-9(H-8) as predominant menaquinone; diphosphatidylglycerol, phosphatidylinositol and phosphatidylglycerol as polar lipids and iso-C-16 : 0 and C-17 : 1 omega 8c as major fatty acids. The proteomic results confirmed the distinct position of ARgP5(T) from its closest neighbours in Frankia cluster 1. ARgP5(T) was found to be infective on two alder (Alnus glutinosa and Alnusalnobetula subsp. crispa) and on one bayberry (Morella pensylvanica) species and to fix nitrogen in symbiosis and in pure culture. On the basis of phylogenetic (16S rRNA gene sequence), genomic, proteomic and phenotypic results, strain ARgP5(T) (= DSM 45898 = CECT 9033) is considered to represent a novel species within the genus Frankia for which the name Frankia canadensis sp. nov., is proposed.