Identification of Ensifer meliloti genes required for survival during peat-based bioinoculant maturation by STM-seq

• Published in: Journal of biotechnology Vol. 362; pp. 12 - 23
• Main Authors: Lozano, Mauricio J., Mogro, Ezequiel G., Eugenia Salas, M., Erdozain, Sofía A., Zuber, Nicolás E., Becker, Anke, Lagares, Antonio
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 20.01.2023
• Subjects: Inoculant; Peat; Phenomics; Rhizobium; Signature tagged mutagenesis; Sinorhizobium meliloti - genetics; Soil; Symbiosis - genetics; Rhizobium; Phenomics; Inoculant; Signature tagged mutagenesis; Peat
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/j.jbiotec.2022.12.004

Rhizobial inoculants are sold either as rhizobia within a liquid matrix; or as rhizobia adhered to granules composed of peat prill or finely ground peat moss. During the production of peat-based inoculants, a series of physiological changes occur that result in an increased capability of the rhizobia to survive on the seeds. The number of viable rhizobia on preinoculated seeds at the point of sale, however, is often a limiting factor, as is the inefficiency of the inoculant bacteria to compete with the local rhizobia for the host colonization. In the present work, we used STM-seq for the genome-wide screening of Ensifer meliloti mutants affected in the survival during the maturation of peat-based inoculant formulations. Through this approach, we were able to identify a set of mutants whose behavior suggests that persistence in peat inoculants involves a complex phenotype that is connected to diverse cellular activities, mainly related to satisfying the requirements of bacterial nutrition (e.g., carbon sources, ions) and to coping with specific stresses (e.g., oxidative, mutational). These results also provide a base knowledge that could be used to more completely understand the survival mechanisms used by rhizobia during the maturation of peat-based inoculants, as well as for the design and implementation of practical strategies to improve inoculant formulations. [Display omitted] •Rhizobial inoculants provide an ecological means of nitrogen fertilization.•Inoculant efficacy could be improved through rational design.•Screening of thousands of Ensifer meliloti mutants on peat-based inoculants (PI).•Stresses faced by rhizobia during PI maturation and storage.•Nutritional limitations faced by rhizobia during PI production.•Help improve the selection of rhizobium strains and the design of inoculants.