Clone libraries of nifH gene fragments specific for the nitrogen-fixing actinomycete Frankia were generated from six soils obtained from five continents using a nested PCR. Comparative sequence analyses of all libraries (n=247 clones) using 96 to 97% similarity thresholds revealed the presence of three and four clusters of frankiae representing the Elaeagnus and the Alnus host infection groups, respectively. Diversity of frankiae was represented by fewer clusters (i.e., up to four in total) within individual libraries, with one cluster generally harboring the vast majority of sequences. Meta-analysis including sequences previously published for cultures (n=48) and for uncultured frankiae in root nodules of Morella pensylvanica formed in bioassays with the respective soils (n=121) revealed a higher overall diversity with four and six clusters of frankiae representing the Elaeagnus and the Alnus host infection groups, respectively, and displayed large differences in cluster assignments between sequences retrieved from clone libraries and those obtained from nodules, with assignments to the same cluster only rarely encountered for individual soils. These results demonstrate large differences between detectable Frankia populations in soil and those in root nodules indicating the inadequacy of bioassays for the analysis of frankiae in soil and the role of plants in the selection of frankiae from soil for root nodule formation.
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http://dx.doi.org/10.1016/j.syapm.2009.07.008 | DOI Listing |
Sci Data
December 2024
Department of Plant Sciences, University of California, Davis, CA, USA.
There have been frequent reports of more than one strain of the nitrogen-fixing symbiont, Frankia, in the same root nodule of plants in the genus Alnus, but quantitative assessments of their relative contributions have not been made to date. Neither has the diversity of other microbes, having potential functional roles in symbiosis, been systematically evaluated. Alnus rubra root nodule microbiota were studied using Illumina short read sequencing and kmer-based read classification.
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September 2024
Plants, Soils, and Climate, College of Agricultural and Applied Sciences, Utah State University, Logan, UT, United States.
Can J Microbiol
December 2024
Department of Biological and Chemical Engineering, USCR Molecular Bacteriology and Genomics, National Institute of Applied Sciences and Technology, University of Carthage, Tunis, Tunisia.
Frankia represent a unique group of filamentous, sporangia-forming bacteria, renowned for their exceptional capacity to establish symbiotic partnerships with actinorhizal plants. The objective of this paper is to offer quantitative insights into the current state of frankia research and its future potential. A comprehensive bibliometric analysis covering the years 2000-2022 was conducted using Scopus and SciVal.
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July 2024
LR Pastoral Ecology, Arid Regions Institute, University of Gabes, Medenine, Tunisia.
Nearly 50 years after the ground-breaking isolation of the primary microsymbiont under axenic conditions, efforts to isolate a substantial number of and strains continue with enduring challenges and complexities. This study aimed to streamline genomic insights through comparative and predictive tools to extract traits crucial for isolating specific in axenic conditions. Pangenome analysis unveiled significant genetic diversity, suggesting untapped potential for cultivation strategies.
View Article and Find Full Text PDFIn root nodule symbioses (RNS) between nitrogen (N)-fixing bacteria and plants, bacterial symbionts cycle between nodule-inhabiting and soil-inhabiting niches that exert differential selection pressures on bacterial traits. Little is known about how the resulting evolutionary tension between host plants and symbiotic bacteria structures naturally occurring bacterial assemblages in soils. We used DNA cloning to examine soil-dwelling assemblages of the actinorhizal symbiont in sites with long-term stable assemblages in ssp.
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