How do bacteria of the genus Microbacterium antagonize the fungus Phakopsora pachyrhizi, the causative agent of Asian soybean rust?

• Grant number: 24/22548-2
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: May 01, 2025
• End date: February 28, 2029
• Field of knowledge: Biological Sciences - Genetics - Molecular Genetics and Genetics of Microorganisms
• Principal Investigator: Paulo José Pereira Lima Teixeira
• Grantee: Carolina Decico Negri
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Plants are colonized by an enormous diversity of microorganisms that form complex communities within all their tissues. These communities, known as microbiomes, significantly influence the interaction of the plant with its environment, playing fundamental roles in plant health and development. The microbiome is considered an extension of the plant immune system, providing an additional layer of protection against pathogens. Consequently, it has been intensively explored as a source of potential biocontrol agents. However, despite its great potential, disease control strategies based on the use of microorganisms often show limited efficiency under commercial cultivation conditions. This is largely due to our limited understanding of the molecular mechanisms governing the interactions between the microbiome, the host plant, and pathogens.In this project, we propose to investigate how bacteria of the genus Microbacterium inhibit the fungus Phakopsora pachyrhizi, the causal agent of Asian soybean rust. In previous work, our research group constructed the Soybiome collection, comprising 3,038 bacteria isolated from soybean and soil. This collection has been explored in search of beneficial bacteria, including those capable of inhibiting pathogenic fungi that attack soybeans. Of the 419 bacteria already evaluated, 69 were able to inhibit the germination of P. pachyrhizi spores in in vitro assays. Notably, the genus Microbacterium emerged as a recurrent inhibitor of this pathogen, including members with efficiency comparable to chemical fungicides. Compared to genera often associated with antibiosis (e.g., Bacillus, Pseudomonas, and Streptomyces), the molecular mechanisms underlying the antifungal action of Microbacterium spp. remain relatively unexplored.Thus, we will use comparative genomics, metabolomics, and genetic manipulation to identify genes and molecules involved in the inhibition of P. pachyrhizi. Our collection also includes Microbacterium isolates lacking antifungal activity, which will serve as a valuable resource for comparative analyses. In addition to investigating molecular mechanisms, we will conduct in planta assays to test protection against Asian soybean rust, using both individual bacteria (monoassociations) and synthetic communities (SynComs). The results of this project are expected to expand our understanding of antifungal activity in plant-associated bacteria, which is essential for the future development of effective biocontrol agents.