GENOME SEQUENCE, TAXONOMIC POSITION, AND SYMBIOTIC GENES OF Ensifer spp. THAT NODULATE Desmanthus virgatus IN NORTH WEST ARGENTINA

ERDOZAIN, S; DEL PAPA, M.F.; ZUBER, N; LOPEZ, JL.; LAGARES, A.; FORNASERO LV.; LOZANO, M.J.

Virtual

Congreso; XV CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE; 2020

SAMIGE

Desmanthus virgatus is a plant species belonging to the Fabaceae family and widely distributed in America in tropical and subtropical regions. D. virgatus is characterized by its high-protein content, drought resistance, and tolerance to the competition by grass plants, thus constituting a promising forage alternative to be used with the livestock in marginal productive areas in Argentina. There is, however, little information on the type and molecular diversity of the rhizobia that nodulate D. virgatus. Based on such considerations in this report we present the genomic analysis of selected D. virgatus nodulating rhizobia available in our laboratory and originally recovered from soil samples collected in the provinces of Salta and Jujuy, Argentina. Out of 27 isolates identified as belonging to the genera Ensifer by MALDI-TOF analysis, 4 of them (2 from Salta and 2 from Jujuy) were selected for their whole genome sequencing using Illumina technology, and for their further analisis.The sizes of the sequenced genomes were close to 6.5 and 7.1 Mb for the isolates from Salta and Jujuy, respectively. While the isolates from Salta were genomically highly similar (ANI 99.95 ? 99.99), the isolates from Jujuy did not to the same extent (ANI 94.15 ? 94.24). Analyses based on the 16S rDNA sequences and on Average Nucleotide Identity (ANI) when genome data were available, served to deduce the phylogenetic position of the sequenced rhizobia. Results indicated that isolates from Salta are phylogenetically close to Ensifer mexicanus (ANI 93.42 - 93.52%), while isolates from Jujuy most likely belong to a new species within the genus Ensifer (ANI values lower than 87 against other Ensifer spp. including the isolates from Salta). The analysis of the symbiotic markers nodA and nifH from both groups of rhizobia revealed substantial differences between them. In congruence with the above ANI, symbiotic genes from the isolates from Salta have their closer relationship with their orthologs from E. mexicanus (unfortunately, we do not know yet whether or not E. mexicanus nodulates Desmanthus). In contrast, the nodA and nifH genes of the isolates from Jujuy have their closer orthologs in E. saheli and E. terangae though these species are distant from the isolates from Jujuy sequenced here (ANI values 81.3 and 86.4 when the isolates from Jujuy are compared against E. saheli and E. terangae, respectively). Such observation strongly support the occurrence of horizontal gene transfer events of symbiotic genes (nod and nif) between genomically diverse Ensifer symbionts of Desmanthus. The results presented here put new light on the diversity of symbiotic genes that support compatible associations with Desmantus, and on the type of chromosomal backgrounds where each symbiotic variant becomes fully functional.