Polyphasic characterization of forage legumes root nodule bacteria isolated from semiarid region in Brazil

Abstract

Forage legumes are important resources in semiarid regions due to their abilities to adapt to soils with low fertility and fix nitrogen when associated with diazotrophic bacteria. Here, we applied a polyphasic approach to characterize a set of legume nodule isolates obtained from Clitoria ternatea and Stylosanthes capitata cultivated in the soils of a semiarid region of Brazil. A total of 126 bacterial isolates were obtained: 45 isolates from C. ternatea and 81 isolates from S. capitata. Nodulation tests revealed only ten isolates that nodulated their original host: six isolates from C. ternatea and four isolates from S. capitata. These ten legume nodule isolates were phenotypically and genotypically characterized. All isolates grew in fructose, glucose, sodium glutamate, maltose, xylose, and sucrose. Metabolic tests showed a relationship between tolerance to salt and high temperatures, where isolates that tolerated the highest salt concentration also tolerated the highest temperature. Three isolates showed amylolytic activity, and four isolates showed carboxymethyl cellulolytic activity. Streptomycin was the most limiting and nalidixic acid was the least limiting antibiotic to bacterial growth. Seven out of ten isolates were indol-acetic acid producers. Additionally, 16S rRNA gene partial sequencing enabled the identification of members of the genera Bacillus (1), Bradyrhizobium (4), Leifsonia (3), Microvirga (1), and Rhizobium (1). These data reveal phenotypically and genotypically diverse bacteria inhabiting the nodules of the forage legumes C. ternatea and S. capitata represent an important microbial source to protect new biotechnological products and improve forage legumes in semiarid regions.

Molecular, Physiological, and Symbiotic Characterization of Cowpea Rhizobia from Soils Under Different Agricultural Systems in the Semiarid Region of Brazil

“…The use of this strategy fits to the selection of bacterial isolates for biotechnological applications as inoculants, due to the increasing of the selection of putative rhizobial over the non-rhizobial strains. In our collection, we obtained a total of 64% of all slow growing isolates as positive for nodC amplification, with 161 positive isolates, in agreement to the isolation of non-rhizobial isolate from nodules in the Brazilian semiarid region (Nunes et al 2018) and in African continent (Mohammed et al 2018).…”

“…As well as observed to the B. vignae related bacteria, the affiliation of ESA 367 indicates that this strain can be member of a new species within Microvirga genus. In addition to M. vignae, other members of Microvirga genus had been recently isolated from soils of the São Francisco River Valley, region where the municipality of Juazeiro is located (Nunes et al 2018;Oliveira et al 2020), showing that members of nodulating clade of Microvirga genus are widespread in these soils.…”

“…Many studies have sought to determine the diversity of native nitrogen-fixing bacteria in Brazilian dry regions (Martins et al 2003;Leite et al 2009;Marinho et al 2017;Santos et al 2017;Rodrigues et al 2018), such as in the Lower Half São Francisco River Valley (Leite et al 2009;Nunes et al 2018). However, these studies did not consider the heterogeneity of the agricultural systems in the region.…”

Are Cowpea-Nodulating Bradyrhizobial Communities Influenced by Biochar Amendments in Soils? Genetic Diversity and Symbiotic Effectiveness Assessment of Two Agricultural Soils of Brazilian Drylands

“…In the São Francisco River Valley, isolates of cowpea-nodulating Microvirga spp. were already isolated (Nunes et al, 2018). In the same basin, the type strain BR 3299 T of M. vignae was isolated in 1996 and the species was described in 2014 (Radl et al 2014), indicating that nodulating Microvirga spp.…”

Phenotypic and Genotypic Characterization of Microsymbionts of Acacia Species Plants Grown in South-Western Saudi Arabia

“…A collection of 75 isolates was obtained from the root nodules of five acacia species from south-western Saudi Arabia and characterized by a polyphasic approach (Nunes et al 2018) including phenotypic, genotypic, and phylogenetic analyses. The results of the plant nodulation tests showed that the majority of isolates were able to nodulate their host of origin.…”