The N-fixing legume Periandra mediterranea constrains the invasion of an exotic grass (Melinis minutiflora P. Beauv) by altering soil N cycling

Melinis minutiflora is an invasive species that threatens the biodiversity of the endemic vegetation of the campo rupestre biome in Brazil, displacing the native vegetation and favouring fire spread. As M. minutiflora invasion has been associated with a high nitrogen (N) demand, we assessed changes in N cycle under four treatments: two treatments with contrasting invasion levels (above and below 50%) and two un-invaded control treatments with native vegetation, in the presence or absence of the leguminous species Periandra mediterranea. This latter species was considered to be the main N source in this site due to its ability to fix N2 in association with Bradyrhizobia species. Soil proteolytic activity was high in treatments with P. mediterranea and in those severely invaded, but not in the first steps of invasion. While ammonium was the N-chemical species dominant in plots with native species, including P.mediterranea, soil nitrate prevailed only in fully invaded plots due to the stimulation of the nitrifying bacterial (AOB) and archaeal (AOA) populations carrying the amoA gene. However, in the presence of P. mediterranea, either in the beginning of the invasion or in uninvaded plots, we observed an inhibition of the nitrifying microbial populations and nitrate formation, suggesting that this is a biotic resistance strategy elicited by P. mediterranea to compete with M. minutiflora. Therefore, the inhibition of proteolytic activity and the nitrification process were the strategies elicited by P.mediterranea to constrain M.munitiflora invasion

Genome Analysis of Endobacterium cerealis, a Novel Genus and Species Isolated from Zea mays Roots in North Spain.

In the present work, we analyse the genomic and phenotypic characteristics of a strain named RZME27T isolated from roots of a Zea mays plant grown in Spain. The phylogenetic analyses of 16S rRNA gene and whole genome sequences showed that the strain RZME27T clustered with the type strains of Neorhizobium galegae and Pseudorhizobium pelagicum from the family Rhizobiaceae. This family encompasses several genera establishing symbiosis with legumes, but the genes involved in nodulation and nitrogen fixation are absent in its genome. Nevertheless, genes related to plant colonization, such as those involved in motility, chemotaxis, quorum sensing, exopolysaccharide biosynthesis and hydrolytic enzymes production were found. The comparative pangenomic analyses showed that 78 protein clusters present in the strain RZME27T were not found in the type strains of its closest relatives N. galegae and P. pelagicum. The calculated average nucleotide identity (ANI) values between the strain RZME27T and the type strains of N. galegae and P. pelagicum were 75.61% and 75.1%, respectively, similar or lower than those found for other genera from family Rhizobiaceae. Several phenotypic differences were also found, highlighting the absence of the fatty acid C19:0 cyclo ω8c and propionate assimilation. These results support the definition of a novel genus and species named Endobacterium cerealis gen. nov. sp. nov. whose type strain is RZME27T

Definition of the novel symbiovar canariense within Mesorhizobium neociceri sp. nov., a new species of genus Mesorhizobium nodulating Cicer canariense in the “Caldera de Taburiente” National Park (La Palma, Canary Islands)

10 páginas, 5 tablas, 4 figurasCicer canariense is a highly promiscuous wild chickpea nodulated by Mesorhizobium strains in La Palma Island located at Canary archipelago. Four of these strains, CCANP34, CCANP35T, CCANP38 and CCANP95 belong to a group phylogenetically close to Mesorhizobium caraganae with 100% similarity values in the 16S rRNA gene. However, the genomes of the strains CCANP35T and M. caraganae LMG 24397T obtained in this work showed ANIb and dDDH values of 90.02% and 44.1%, respectively. These values are lower than those currently accepted for different bacterial species showing that the Canarian strains do not belong to the species M. caraganae. The Canarian strains also differ from M. caraganae in the amounts of several fatty acids and in several phenotypic traits. Based on the obtained results the Canarian strains belong to a novel species for which we propose the name Mesorhizobium neociceri sp. nov. and whose type strain is CCANP35T. The results of the phylogenetic analyses of nodC and nifH symbiotic genes showed that the Canarian strains represent a novel symbiovar within genus Mesorhizobium phylogenetically divergent to that encompassing M. caraganae. We propose the names canariense and caraganae for the symbiovars encompassing the strains of M. neociceri and M. caraganae, respectively.This work was supported by Grant 111/2010 from Organismo Autónomo de Parques Nacionales (Ministerio de Medio Ambiente y Medio Rural y Marino, España). JDFF is currently a recipient of a postdoctoral Marie Skłodowska-Curie Fellowship No 101003373. The authors thank to Dr Aharon Oren for his valuable help with naming the new species. The authors also thank the Strategic Research Programs for Units of Excellence CLU-2O18-04 (University of Salamanca) and CLU-2019-05 (IRNASA/CSIC) co-funded by the Junta de Castilla y León and European Union (ERDF “Europe drives our growth”).Peer reviewe