Polyphasic study of Zymomonas mobilis strains revealing the existence of a novel subspecies Z. mobilis subsp. francensis subsp. nov., isolated from French cider

Abstract

Zymomonas mobilis strains recently isolated from French 'framboisé' ciders were compared with collection strains of the two defined subspecies, Z. mobilis subsp. mobilis and Z. mobilis subsp. pomaceae, using a polyphasic approach. Six strains isolated from six different regions of France were compared with three strains of Z. mobilis subsp. mobilis, including the type strain LMG 404T, and four strains of Z. mobilis subsp. pomaceae, including the type strain LMG 448T, using phenotypic and genotypic methods. For phenotypic characterization, both physiological tests and SDS-PAGE protein profiles revealed significant differences between the two known subspecies and the French isolates; three distinct groups were observed. These findings were further confirmed by random amplified polymorphic DNA and repetitive extragenic palindromic-PCR genotyping methods in which the French isolates were clearly distinguished from the other two subspecies. Sequence analysis of a fragment ranging from 604 to 617 nucleotides corresponding to the 16S-23S rRNA gene intergenic spacer region (ISR), a 592 nucleotide HSP60 gene fragment and a 1044 nucleotide gyrB gene fragment confirmed the presence of three distinct groups. The French strains exhibited almost 94 % similarity to the ISR, 90 % to HSP60 and 86 % to gyrB sequences of the three collection strains of Z. mobilis subsp. mobilis and 87, 84 and 80 % sequence similarity, respectively, was observed with the four Z. mobilis subsp. pomaceae strains. Based on both the phenotypic and genotypic results, the French strains are proposed to represent a novel subspecies, Zymomonas mobilis subsp. francensis subsp. nov. Strain AN0101T (= LMG 22974T = CIP 108684T) was designated as the type strain.