Rhizobia–Soybean Interactions Laboratory

Development of methods to understand how rhizobia move within the complex structure of soil.

Soil is a dark, tortuous and irregular environment where bacterial movement cannot be observed directly at high resolution. In addition, its water content varies in time and space: rhizobia swim by means of their flagella when water is available and apparently move near the internal surfaces of pores.

We use specific mutants and experimental designs that simulate soil conditions to measure dispersal rates, movement characteristics and energy used.

Participants: María Julia Althabegoiti and Aníbal R. Lodeiro.

Study of rhizobial motility as a factor in colonization and competition for nodulation.

The motility of species used in biofertilizers can influence their ability to colonize roots and compete for nodulation. In the laboratory, artificial selection yielded a more motile mutant that proved more competitive in the field and increased soybean crop yield.

We currently analyze the genetic changes that led to that phenotype, including those that did not occur directly in genes related to the flagellum or chemotaxis.

Participants: María Julia Althabegoiti and Aníbal R. Lodeiro.

Characterization of the two flagellar systems and of the signals that regulate their expression.

We genomically analyze the genes encoding the two flagellar systems expressed by B. diazoefficiens and study how they respond to environmental signals, such as carbon source and medium viscosity.

We also investigate the involvement of histidine kinases and of the second messenger c-di-GMP in the regulation of these systems, combining genetic, biochemical and functional approaches.

Participants: Elías Mongiardini, Julián Iglesias and Aníbal R. Lodeiro.

Development of improved inoculants to increase the productivity of soybean crops.

We work on a granulated biofertilizer that allows better distribution of rhizobia in the seeding furrow and favors the establishment of symbiosis.

The development combines symbiotic strains with plant growth–promoting bacteria, seeking an efficient formulation for direct application in agricultural systems.

Participants: Julieta Pérez Giménez and Aníbal R. Lodeiro.

Analysis of the bacterial response to nutrient scarcity and of its effects on symbiosis.

We study the stringent response of B. diazoefficiens to nutritional limitation and its influence on the symbiotic interaction with soybean.

The project combines comparative transcriptomic and proteomic studies in mutants of the rsh gene with functional validation of genes involved in the plant–bacterium interaction.

Participants: Ornella Faldutti and Julieta Pérez Giménez.

Selection of rhizosphere communities and microbial consortia to improve biological nitrogen fixation.

We explore artificial ecosystem selection as a strategy to identify rhizosphere communities with functional traits beneficial for soybean.

Symbiotic consortia capable of sustaining more efficient nitrogen fixation are characterized, with the aim of developing more effective and sustainable bioinoculants.

Participants: Damián Brignoli, Julieta Pérez Giménez and Aníbal R. Lodeiro.

Study of the regulatory circuits that enable adaptation to environmental stresses and sustain symbiotic nitrogen fixation.

We analyze the Two-Component Systems of B. diazoefficiens involved in the response to different abiotic stresses and their relationship with symbiotic efficiency in soybean plants.

The work integrates biochemical, genetic, molecular biology and omics strategies to understand how the physiological and metabolic conditions of rhizobia modulate the interaction. In the future, this knowledge may be applied to the development and formulation of better inoculants.

Participants: Silvina Laura López García and Juliana Belén Heredia.