Rhizobiaceae is one of the most representative families, encompassing rhizobial species, valuable allies in the sustainable production of legumes such as cowpea ( Vigna unguiculata ). Interestingly, beyond rhizobia, studies have increasingly reported the presence of a wide diversity of non-symbiotic bacteria that compose the microbiome of cowpea nodules. In this study, we performed a systematic analysis, with an emphasis on phylogenomic aspects, of 12 strains trapped from cowpea in soils of indigenous lands in Mato Grosso do Sul, Central-Western Brazil (Cerrado biome), which had been preliminarily characterized. The results highlighted the rich and little-explored Rhizobiaceae biodiversity, revealing a novel genus, Brasilibacterium gen. Nov., and three novel species: Brasilibacterium cachoeirinhense sp. nov. (CNPSo 3794 T = BR 15710 T = LMG 34800 T ), Brasilibacterium lagoinhense sp. nov. (CNPSo 3920 T = BR 15708 T = 34801 T ), and Martinezella lalimensis sp. nov. (CNPSo 3959 T = BR 15709 T = LMG 34802 T ). However, none of the strains belonging to these novel species was able to re-nodulate cowpea or the promiscuous legumes Phaseolus vulgaris and Macroptilium atropurpureum , suggesting either the loss of symbiotic genes or their endophytic nature. In addition to the novel species accessed, “ Rhizobium atlanticum ”, “ Martinezella aureum ”, “ Martinezella centroccidentale ”, “ Martinezella hainanensis” , and “ Martinezella dioscoreae” were also identified based on genomic sequences, with the latter two reported for the first time in Brazil.
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Delai et al. (2026) studied this question.
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