A study led by researchers from the Department of Biotechnology and Environmental Protection at EEZ CSIC, in collaboration with the Center for Genomic Sciences at UNAM in Mexico, demonstrates for the first time that volatile compounds emitted by rhizobia have measurable effects on both soil microbiomes and those associated with a legume plant.
Bacteria release complex mixtures of volatile compounds, known as the "volatilome", which exhibit a range of biological activities affecting microorganisms and plants. However, their effects on natural microbiomes, which play a key role in overall ecosystem health, have been scarcely investigated. In the case of rhizobia, a group of bacteria widely used as legume inoculants to improve crop productivity, knowledge of their volatile compounds and associated bioactivity remains particularly limited.
In the study, published in Microbiological Research, the researchers used Sinorhizobium meliloti, a model rhizobium species commonly employed in the study of plant bacterium interactions. The team analysed the composition of volatile compounds emitted by a wild type strain of S. meliloti and by mutant strains derived from it, identifying several compounds, most notably methyl ketones and fatty acid methyl esters.
The researchers then assessed how microbial populations were affected after exposing natural soil and Medicago truncatula plants to different S. meliloti volatilome mixtures, as well as to some of its pure methyl ketones. The most relevant finding indicates that exposing plants to S. meliloti volatilomes helps maintain rhizobial populations associated with plant roots over time, a factor that could have direct implications for plant health.
This work contributes to expanding knowledge of the biosynthetic pathways involved in bacterial volatile compound production and represents the first study to address the ecological role of rhizobial volatilomes in natural microbiomes. The results highlight the complexity of the chemical dialogue operating in plant bacterium interactions and open up new avenues for application in sustainable agriculture.
The article, published in open access, is available at the following link:
https://doi.org/10.1016/j.micres.2026.128456
Source: eez.csic.es
