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[This corrects the article on p. 1154 in vol. 8, PMID: 28694797.].

Although the taxonomy of Burkholderia has been extensively scrutinized, significant uncertainty remains regarding the generic boundaries and composition of this large and heterogeneous taxon. Here we used the amino acid and nucleotide sequences of 106 conserved proteins from 92 species to infer robust maximum likelihood phylogenies with which to investigate the generic structure of Burkholderia sensu lato. These data unambiguously supported five distinct lineages, of which four correspond to Burkholderia sensu stricto and the newly introduced genera Paraburkholderia, Caballeronia, and Robbsia. The fifth lineage was represented by P. rhizoxinica. Based on these findings, we propose 13 new combinations for those species previously described as members of Burkholderia but that form part of Caballeronia. These findings also suggest revision of the taxonomic status of P. rhizoxinica as it is does not form part of any of the genera currently recognized in Burkholderia sensu lato. From a phylogenetic point of view, Burkholderia sensu stricto has a sister relationship with the Caballeronia+Paraburkholderia clade. Also, the lineages represented by P. rhizoxinica and R. andropogonis, respectively, emerged prior to the radiation of the Burkholderia sensu stricto+Caballeronia+Paraburkholderia clade. Our findings therefore constitute a solid framework, not only for supporting current and future taxonomic decisions, but also for studying the evolution of this assemblage of medically, industrially and agriculturally important species.

South Africa is well-known for the diversity of its legumes and their nitrogen-fixing bacterial symbionts. However, in contrast to their plant partners, remarkably few of these microbes (collectively referred to as rhizobia) from South Africa have been characterised and formally described. This is because the rules of the International Code of Nomenclature of Prokaryotes (ICNP) are at odds with South Africa's National Environmental Management: Biodiversity Act and its associated regulations. The ICNP requires that a culture of the proposed type strain for a novel bacterial species be deposited in two international culture collections and be made available upon request without restrictions, which is not possible under South Africa's current national regulations. Here, we describe seven new Mesorhizobium species obtained from root nodules of Vachellia karroo , an iconic tree legume distributed across various biomes in southern Africa. For this purpose, 18 rhizobial isolates were delineated into putative species using genealogical concordance, after which their plausibility was explored with phenotypic characters and average genome relatedness. For naming these new species, we employed the rules of the recently published Code of Nomenclature of Prokaryotes described from Sequence Data (SeqCode), which utilizes genome sequences as nomenclatural types. The work presented in this study thus provides an illustrative example of how the SeqCode allows for a standardised approach for naming cultivated organisms for which the deposition of a type strain in international culture collections is currently problematic. [ABSTRACT FROM AUTHOR]

Bradyrhizobium is thought to be the largest and most diverse rhizobial genus, but this is not reflected in the number of described species. Although it was one of the first rhizobial genera recognised, its taxonomy remains complex. Various contemporary studies are showing that genome sequence information may simplify taxonomic decisions. Therefore, the growing availability of genomes for Bradyrhizobium will likely aid in the delineation and characterization of new species. In this study, we addressed two aims: first, we reviewed the availability and quality of available genomic resources for Bradyrhizobium. This was achieved by comparing genome sequences in terms of sequencing technologies used and estimated level of completeness for inclusion in genome-based phylogenetic analyses. Secondly, we utilized these genomes to investigate the taxonomic standing of Bradyrhizobium in light of its diverse lifestyles. Although genome sequences differed in terms of their quality and completeness, our data indicate that the use of these genome sequences is adequate for taxonomic purposes. By using these resources, we inferred a fully resolved, well-supported phylogeny. It separated Bradyrhizobium into seven lineages, three of which corresponded to the so-called supergroups known for the genus. Wide distribution of key lifestyle traits such as nodulation, nitrogen fixation and photosynthesis revealed that these traits have complicated evolutionary histories. We present the first robust Bradyrhizobium species phylogeny based on genome sequence information for investigating the evolution of this important assemblage of bacteria. Furthermore, this study provides the basis for using genome sequence information as a resource to make important taxonomic decisions, particularly at the species and genus levels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bradyrhizobium species isolated from diverse legumes in South Africa. • Delineation of these species following the genealogical concordance approach. • Novel Bradyrhizobium species represent nodA alleles specific to South African Clades. • Bradyrhizobium species may have agricultural importance in sub-Saharan Africa. Africa is known for its rich legume diversity with a significant number of endemic species originating in South Africa. Many of these legumes associate with rhizobial symbionts of the genus Bradyrhizobium , of which most represent new species. Yet, none of the Bradyrhizobium species from South Africa have been described. In this study, phylogenetic analysis of 16S rRNA gene sequences of fourteen strains isolated in southern Africa from root nodules of diverse legumes (i.e., from the tribes Crotalarieae, Acacieae, Genisteae, Phaseoleae and Cassieae) revealed that they belong to the Bradyrhizobium elkanii supergroup. The taxonomic position and possible novelty of these strains were further interrogated using genealogical concordance of five housekeeping genes (atpD, dnaK, glnII, gyrB and rpoB). These phylogenies consistently recovered four monophyletic groups and one singleton within Bradyrhizobium. Of these groups, two were conspecific with Bradyrhizobium brasilense UFLA 03-321T and Bradyrhizobium ivorense CI-1BT, while the remaining three represented novel taxa. Their existence was further supported with genome data, as well as metabolic and physiological traits. Analysis of nodA gene sequences further showed that the evolution of these bacteria likely involved adapting to local legume hosts and environmental conditions through the acquisition, via horizontal gene transfer, of optimal symbiotic loci. We accordingly propose the following names Bradyrhizobium acaciae sp. nov. 10BBT (SARCC 730T = LMG 31409T), Bradyrhizobium oropedii sp. nov. Pear76T (SARCC 731T = LMG 31408T), and Bradyrhizobium altum sp. nov. Pear77T (SARCC 754T = LMG 31407T) to accommodate three novel species, all of which are symbionts of legumes in South Africa. [ABSTRACT FROM AUTHOR]