The discovery paves the way for the development of new agricultural biotechnologies that are more sustainable and based on Brazilian biodiversity Researchers have found in the Campos Rupestres – mountaintop grasslands that are a biodiversity hotspot in Brazil– – an unprecedented diversity of microorganisms that are highly specialized in capturing and recycling the phosphorus available in the soil. The discovery paves the way for the development of new agricultural biotechnologies aimed at increasing agricultural cultivars' phosphorus absorption and simultaneously reducing the use of chemical fertilizers. The research was published yesterday (19) on The ISME Journal by researchers from the Genomics for Climate Change Research Center (GCCRC) – an Engineering Research Center (ERC) constituted by Embrapa and the State University of Campinas (Unicamp), funded by the São Paulo State Research Support Foundation (FAPESP). Campos Rupestres are located in the central region of Brazil. They are considered a biodiversity hotspot because they concentrate many single-occurring species in this region that are currently threatened by mining and animal farming activities. “The soil of this ecosystem is extremely poor in phosphorus and very acidic due to geological conditions. In spite of that, this ecosystem harbors almost 15% of the Brazilian plant diversity, and this intrigued us a lot, since it is an apparently hostile environment for plant development,” explains Isabel Gerhardt, a researcher at Embrapa Digital Agriculture and GCCRC and one of the authors of the study. “There have been a lot of studies about the physiology of these plants in order to understand how they grow in this ecosystem, but from the perspective of nutrition associated with microorganisms, it is a first,” says Antônio Camargo, first author of the study developed during his PhD at the GCCRC with a FAPESP scholarship. Soil nutrients are not always in a form that plants can absorb, but microorganisms can make such nutrients soluble for the plants to absorb. An example is mycorrhiza, a group of fungi that colonizes roots and helps plants absorb nutrients from the soil, and Bradyrizobia, bacteria that helps plants absorb nitrogen. In the case of phosphorus, its absorption is known to be intermediated by microorganisms. The differential of the GCCRC study was to find a large diversity and abundance of bacteria that are highly efficient in making phosphorus available to plants in an environment where this element is poorly available. “We found many families of phosphorus-associated bacteria with about 25 percent more genes involved in the solubilization of the nutrient than those previously catalogued,” Camargo states. To reach those conclusions, the researchers studied two plants of the Velloziacea family that are typical of Campos Rupestres. One grows in the soil and the other on rocks. They then collected samples from the plants, soil and rocks to analyze the microorganisms present there. All genetic material was sequenced and compared to public microbial gene banks. A total of 522 genomes were identified, half of which were new to science. The study added 21 new families of bacteria. Some understudied phyla have been significantly expanded, as are the cases of the phyla Eremiobacterota and Acidobacteria. By comparing the genomes of bacteria from plants that grew on local soil and rocks, the researchers found that those were very different communities, but with overlapping species. “The most interesting thing is that the bacteria associated with phosphorus tend to be shared by the two plants and are very abundant,” Camargo adds. Another aspect the group analyzed was whether the high number of genes related to phosphorus solubilization by the bacteria from Campos Rupestres was a general trait of the families described therein. To do this, the scientists compared the frequency of these genes with evolutionarily related bacteria found elsewhere. “We found that bacteria from Campos Rupestres tend to have more phosphorus solubilization genes indeed,” Camargo explained. In the search for this rare nutrient in the environment, plants also do their part. The researchers have shown that they secrete solutions that attract bacteria through their roots. “Plants recruit microorganisms that solubilize phosphorus by having their roots secrete organic compounds such as aminoacids and organic acids that recruit such microorganisms,” the authors explain. “These findings show that Campos Rupestres harbor an enormous genetic repertoire that is still little known to science. All this information can generate valuable technological assets in a bioeconomy model,” Gerhardt adds. “This is another reason to seek the sustainable use of those areas and the preservation of the biodiversity that exists there,” the researcher concludes. Sustainable biotechnological solutions One of the expected developments from the published study is to help to select phosphorus-solubilizing bacteria to support new agricultural biofertilizer technologies. Phosphorus is one of the three macronutrients that are most used in crop fertilization in Brazil with the lowest rates of crop uptake in Brazilian tropical soils. About 55% of phosphate fertilizers are imported, especially from mines in Morocco, but also from Russia, Egypt, China and the USA. Today, in order to maintain yields high, it is necessary to add phosphate fertilizers to the fields, which causes economic and environmental impacts. “We see in this new discovery the possibility of developing a bioproduct to address at least three important issues for the country. The first is reducing dependence on the foreign supply of this fertilizer, which showed its vulnerability with the war in Ukraine. The second aspect is the fact that phosphorus is a non-renewable mineral resource that is in the process of depletion. Finally, the third point is greenhouse gas emissions. A kilo of greenhouse gases is emitted for each kilo of phosphate fertilizer”, points out Rafael Souza, associate researcher at GCCRC and one of the authors of the article. Souza is the cofounder of Symbiomics, a Brazilian biotech startup that focuses on the development of next-generation biological products. There are already inspirations for the use of biofertilizers. Today, 80% of the soybean planted area in the country resorts to biofertilizers. This represents savings of approximately US$10 billion in nitrogen fertilizers. “This work shows that here in Brazil we can use biodiversity to find more sustainable solutions for food production,” concludes Souza. About GCCRC The Genomics for Climate Change Research Center (GCCRC) is a joint Embrapa/Unicamp research center, whose main mission is to create biotechnological assets through genomics applied to the adaptation of crops to the stresses associated with climate change. The GCCRC has built and expanded the Joint Research Unit for Genomics Applied to Climate Change (UMiP GenClima), an initiative established in 2012 by Embrapa and Unicamp . The center gathered scientists in a state-of-the-art laboratory funded by FAPESP through the Engineering Research Centres program and the Microbiome Support Program, funded by the European Union's research and innovation program Horizon 2020. Access the paper 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.