1887

Abstract

Arbuscular mycorrhizal fungi are obligate endosymbionts that colonize the roots of almost 80 % of land plants. The present paper describes morphological and molecular data on a bacterial endosymbiont living in the cytoplasm of dormant or germinating spores and symbiotic mycelia of the fungal species , and . PCR amplification of almost the entire 16S rRNA gene of the BEG 34 endosymbiont, using universal bacterial primers, and subsequent sequence analysis demonstrated that this organism occupies a very distinct phylogenetic position within the β-, with the genera , and as its closest neighbours. Primers specific to the 16S rDNA of the endosymbiotic bacteria of BEG 34 allowed amplification of spore DNA from endosymbionts of , , and , but not from the endosymbiont (which was morphologically different) or from the cytoplasm of (which did not contain endosymbiotic bacteria). These specific primers were successfully used as a probe for the hybridization of endobacteria in spores. The overall rod-shaped morphology of the , , and endosymbionts was similar, and amplification and sequence analysis of the almost-complete 16S rRNA genes of several , and endosymbionts revealed over 98 % sequence similarity. These morphological and genomic characteristics were used to assign the endosymbionts of these three species (five isolates) of arbuscular mycorrhizal fungi as ‘ Glomeribacter gigasporarum’ gen. nov., sp. nov.

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2003-01-01
2020-07-12
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