Evaluation of phage depolymerases against Xanthomonas citri subsp. citri

• Grant number: 24/13851-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2024
• End date: September 30, 2025
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Henrique Ferreira
• Grantee: Gabriel Felicio Silva
• Host Institution: Instituto de Biociências (IB). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil
• Associated research grant: 21/10577-0 - Biology of Bacteria and Bacteriophages Research Center, AP.CEPID

Abstract

Bacteriophages, natural viruses that specifically infect bacteria, have been extensively studied since their discovery due to their potential for treating bacterial infections. Although their application declined with the introduction of penicillin, the resurgence of phage therapy in recent decades has been driven by the growing bacterial resistance to antibiotics, making essential the search for effective therapeutic alternatives. However, the efficacy of phages is often limited by the presence of bacterial biofilms, which are complex aggregates of microorganisms protected by a matrix of extracellular polymeric substances (EPS), which constitutes a significant physical barrier against the action of phages and antibiotics. To overcome this difficulty, some phages encode enzymes known as depolymerases, which degrade EPS components, facilitating the adsorption of phages to bacterial cells. These depolymerases act by removing the protective layers of bacterial cells, exposing them to antibacterial agents and the phages themselves. The potential application of these enzymes in agriculture is promising, especially in the prevention of bacterial colonization such as citrus canker, caused by the bacterium Xanthomonas citri subsp. citri (X. citri). Xanthan gum, the main EPS produced by X. citri, contributes to the epiphytic survival of the bacterium and the severity of symptoms in infected plants. The application of phage depolymerases could degrade this gum, reducing bacterial survival and the need for higher doses of copper, currently used in disease control. Despite the potential of depolymerases, the identification of genes encoding these enzymes in phages that infect X. citri is still limited. The advancement of bioinformatics tools aims to facilitate the search for depolymerase sequences, with notable examples being PhageDPO, DepoScope, and PhageDePP. However, these tools are recent and lack extensive validation. Therefore, it is necessary to identify new depolymerase candidates using available bioinformatics tools and to evaluate the activity of these enzymes against X. citri.