International audienceThe use of phosphate-solubilizing bacteria (PSB) as inoculants simultaneously increases P uptake by the plant and crop yield. A method to isolate efficient strains, an overview of some updated molecular techniques useful in their characterization (16S rRNA sequencing, LMW RNA profiles, TP-RADP and rep-PCR fingerprinting) and a method for obtaining strain-specific DNA probes will be briefly explained. These methodologies are not time-consuming and, in general, do not require sophisticated equipment.Les bactéries qui solubilisent les phosphates comme inoculants en agriculture : utilisation de techniques moléculaires récentes pour leur étude. L'utilisation de bactéries qui solubilisent les phosphates comme inoculants augmente en même temps l'absorption de cet élément par la plante ainsi que le rendement des cultures. Cet article contient une brève revue des techniques récentes de biologie moléculaire utilisées pour caractériser ces bactéries (séquençage du 16S RNA, profils de LMW RNA, et empreintes par TP-RAPD et rep-PCR). On présente aussi une méthode d'isolation de souches efficientes pour la solubilisation du phosphate et une méthode pour obtenir des sondes d'ADN spécifiques des souches. Il s'agit de méthodes rapides qui, en général, n'ont pas besoin d'un équipement sophistiqué

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Plants harbor a diversity of microorganisms constituting the plant microbiome. Many bioinoculants for agricultural crops have been isolated from plants. Nevertheless, plants are an underexplored niche for the isolation of microorganisms with other biotechnological applications. As a part of a collection of canola endophytes, we isolated strain CDVBN77T. Its genome sequence shows not only plant growth-promoting (PGP) mechanisms, but also genetic machinery to produce secondary metabolites, with potential applications in the pharmaceutical industry, and to synthesize hydrolytic enzymes, with potential applications in biomass degradation industries. Phylogenetic analysis of the 16S rRNA gene of strain CDVBN77T shows that it belongs to the genus Microvirga, its closest related species being M. aerophila DSM 21344T (97.64% similarity) and M. flavescens c27j1T (97.50% similarity). It contains ubiquinone 10 as the predominant quinone, C19:0 cycloω8c and summed feature 8 as the major fatty acids, and phosphatidylcholine and phosphatidylethanolamine as the most abundant polar lipids. Its genomic DNA G+C content is 62.3 (mol %). Based on phylogenetic, chemotaxonomic, and phenotypic analyses, we suggest the classification of strain CDVBN77T within a new species of the genus Microvirga and propose the name Microvirga brassicacearum sp. nov. (type strain CDVBN77T = CECT 9905T = LMG 31419T).

Soil microbiology could be affected by the presence of pesticide residues during intensive farming, potentially threatening the soil environment. The aim here was to assess the dissipation of the herbicides triasulfuron and prosulfocarb, applied as a combined commercial formulation, and the changes in soil microbial communities (through the profile of phospholipid fatty acids (PLFAs) extracted from the soil) during the dissipation time of the herbicides under field conditions. The dissipation of herbicides and the soil microbial structure were assessed under different agricultural practices, such as the repeated application of herbicides (twice), in unamended and amended soils with two organic amendments derived from green compost (GC1 and GC2) and with non-irrigation and irrigation regimes. The results obtained indicate slower dissipation for triasulfuron than for prosulfocarb. The 50% dissipation time (DT) decreased under all conditions for the second application of triasulfuron, although not for prosulfocarb. The DT values for both herbicides increased in the GC2 amended soil with the highest organic carbon (OC) content. The DT values decreased for prosulfocarb with irrigation, but not for triasulfuron, despite its higher water solubility. The herbicides did not have any significant effects on the relative population of Gram-negative and Gram-positive bacteria during the assay, but the relative abundance of Actinobacteria increased in all the soils with herbicides. At the end of the assay (215 days), the negative effects of herbicides on fungi abundance were significant (p < 0.05) for all the treatments. These microbiological changes were detected in non-irrigated and irrigated soils, and were more noticeable after the second application of herbicides. Actinobacteria could be responsible for the modification of herbicide degradation rates, which tend to be faster after the second application. This study makes a useful contribution to the evaluation of the soil environment and microbiological risks due to the long-term repeated application of herbicides under different agricultural management practices.