The discovery paves the way for the development of a more sustainable agriculture based on biodiversity traits.
Researchers found an unprecedented diversity of microorganisms highly specialized in capturing and recycling available phosphorus in the campos rupestres – a biodiversity hotspot in Brazil. The discovery paves the way for the development of new agricultural biotechnological solutions aimed at increasing the absorption of phosphorus by agricultural cultivars and, simultaneously, reducing the use of chemical fertilizers.
The research was published yesterday (19) by researchers from the Center for Research in Genomics Applied to Climate Change (GCCRC, Brazil), and Joint Genome Institute (JGI, USA).
The campos rupestres are located in the central region of Brazil. They are considered a biodiversity hotspot because they concentrate many unique species that are currently threatened by mining and livestock activities. “The soil of this ecosystem is extremely poor in phosphorus and very acidic, due to the geological conditions. Despite this, this ecosystem comprises around 15% of Brazilian plant diversity, what fascinated us since apparently it is a hostile environment for the development of plants”, explains Isabel Gerhardt, researcher at Embrapa Agricultura Digital and GCCRC and one of the authors of the study.
“A lot has already been studied about the physiology of these plants with the objective of understanding how they grow in this ecosystem, but from the perspective of plant nutrition through microorganisms it is the first time”, says Antonio Camargo, first author of the study and JGI scientist, who developed this study during his PhD at GCCRC.
Soil nutrients are not always in a form that plants can absorb, but microorganisms are able to make these nutrients soluble for plant uptake. An example are the mycorrhiza, associations between fungi and plant roots that help the plant to absorb nutrients from the soil, and Bradyrizobium, a group of bacteria that helps the plant to absorb nitrogen.
In the case of phosphorus, it is already known that its absorption is mediated by microorganisms. The differential of the current study was to find great diversity and abundance of bacteria that are highly efficient in making phosphorus available to the plant in an environment where this element is scarcely available. “We found many families of bacteria associated with phosphorus with around 25% more nutrient solubilization genes than those previously cataloged”, explains Camargo.
To arrive at these conclusions, the researchers studied two typical plants from the campos rupestres: Vellozia epidendroides and Barbacenia macrantha, from the Velloziacea family. The former grows in the ground and latter, in the rock. They collected samples of the plants, soil and rocks to analyze the microorganisms. From DNA sequence data generated at the JGI, 522 genomes were identified, half of which were new to science. The study added 21 new families of bacteria. Some little-studied phyla are significantly expanded, as is the case of the phyla Eremiobacterota and Acidobacteria. By comparing the genomes of bacteria from plants that grew in rock and soil, the researchers found that these are very different communities, yet they share overlapping species. “The most interesting thing is that they tend to be shared between the two plants and are very abundant”, adds Camargo.
Another aspect investigated by the group was to understand whether or not the high number of genes related to phosphorus solubilization in the Campos Rupestres bacteria was a common trait of the overall group described there. They compared the frequency of these genes with evolutionarily related bacteria found elsewhere. “We discovered that the bacteria from Campos Rupestres actually tend to have more phosphorus solubilization genes”, explained Camargo.
In this search for this poorly available nutrient in the environment, plants also play their role. The researchers showed that the plants secrete compounds out of their roots to attract bacteria. “Plants recruit microorganisms that solubilize phosphorus by secreting organic compounds such as amino acids and organic acids in their roots that attract microorganisms”, explain the authors.
“These results show us that the Campos Rupestres harbor an enormous genetic repertoire that is still little known by science. All this information can generate valuable technological assets in a bioeconomy model”, adds Gerhardt. “This is one more reason for us to seek the sustainable use of these areas and the preservation of the existing biodiversity”, concludes the researcher.
Sustainable biotechnological solutions
One of the expectations of the published study is to help select phosphorus-solubilizing bacteria to support new agricultural biofertilizer technologies.
The total global application of P fertilizer on croplands had increased over three times in 50 years and it is projected to increase to 22–27 teragram by 2050. Overuse and improper use of phosphorus in crop production result in leaching it to adjacent water bodies, causing pollution and threatening the health of aquatic organisms and humans.
Phosphorus is one of the three most used macronutrients in the fertilization of crops in Brazil. About 55% of phosphate fertilizers are imported, mainly from mines in Morocco, but also from Russia, Egypt and China.
“We see in this new discovery the possibility of developing a bioproduct to tackle at least three important issues for Brazil. The first is the reduction of external dependence on the supply of this fertilizer, which showed its vulnerability with the Russo-Ukrainian war. The second aspect is the fact that phosphorus is a non-renewable mineral resource that is running out. Finally, the third point is the emission of greenhouse gases. For each kilogram of phosphate fertilizer, one kilogram of greenhouse gases is emitted,” points out Rafael Souza, an associate researcher at the GCCRC and one of the authors of the article. Souza is the co-founder of Symbiomics, a Brazilian biotechnology startup focused on the development of next-generation biologics.
Inspirations for the use of biofertilizers already exist. Today, 80% of the soybean planted area in the country uses biofertilizers. This represents savings of approximately US$ 10 billion in nitrogen fertilizer.
“This work shows that here in Brazil we can use biodiversity to find more sustainable solutions for food production”, concludes Souza.
About the GCCRC
The Genomic Research Center for Climate Change (GCCRC) is a joint Embrapa/Unicamp Research Center whose main mission is the creation of biotechnological assets through genomics applied to the adaptation of crops to the stresses associated with climate change. The GCCRC built and expanded the Joint Research Unit in Genomics Applied to Climate Change (UMiP GenClima), an initiative between Embrapa and Unicamp established in 2012. The GCCRC brought together scientists in a state-of-the-art laboratory funded by FAPESP through the Centros de Engineering Research (ERC) and the Microbiome Support Programme, funded by the European Union’s Horizon 2020 research and innovation programme.
Access the article
Antonio P. Camargo, Rafael S. C. de Souza, Juliana Jose, Isabel R. Gerhardt, Ricardo A. Dante, Supratim Mukherjee, Marcel Huntemann, Nikos C. Kyrpides, Marcelo F. Carazzolle and Paulo Arruda. Plant microbiomes harbor potential to promote nutrient turnover in impoverished substrates of a Brazilian biodiversity hotspot. ISME J. (2022) https://doi.org/10.1038/s41396-022-01345-1.