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Walker NC, White SM, Ruiz SA, McKay Fletcher D, Saponari M, Roose T. A mathematical model of biofilm growth and spread within plant xylem: Case study of Xylella fastidiosa in olive trees. J Theor Biol 2024; 581:111737. [PMID: 38280544 DOI: 10.1016/j.jtbi.2024.111737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 11/16/2023] [Accepted: 01/10/2024] [Indexed: 01/29/2024]
Abstract
Xylem-limited bacterial pathogens cause some of the most destructive plant diseases. Though imposed measures to control these pathogens are generally ineffective, even among susceptible taxa, some hosts can limit bacterial loads and symptom expression. Mechanisms by which this resistance is achieved are poorly understood. In particular, it is still unknown how differences in vascular structure may influence biofilm growth and spread within a host. To address this, we developed a novel theoretical framework to describe biofilm behaviour within xylem vessels, adopting a polymer-based modelling approach. We then parameterised the model to investigate the relevance of xylem vessel diameters on Xylella fastidiosa resistance among olive cultivars. The functionality of all vessels was severely reduced under infection, with hydraulic flow reductions of 2-3 orders of magnitude. However, results suggest wider vessels act as biofilm incubators; allowing biofilms to develop over a long time while still transporting them through the vasculature. By contrast, thinner vessels become blocked much earlier, limiting biofilm spread. Using experimental data on vessel diameter distributions, we were able to determine that a mechanism of resistance in the olive cultivar Leccino is a relatively low abundance of the widest vessels, limiting X. fastidiosa spread.
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Affiliation(s)
- N C Walker
- Bioengineering Sciences Research Group, Department of Mechanical Engineering, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, SO17 1BJ, UK
| | - S M White
- UK Centre for Ecology & Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
| | - S A Ruiz
- Bioengineering Sciences Research Group, Department of Mechanical Engineering, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, SO17 1BJ, UK
| | - D McKay Fletcher
- Bioengineering Sciences Research Group, Department of Mechanical Engineering, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, SO17 1BJ, UK; Rural Economy Environment and Society Research Group, SRUC, Edinburgh EH9 3JG, UK
| | - M Saponari
- Istituto per la Protezione Sostenibile delle Piante, CNR, Bari, Italy
| | - T Roose
- Bioengineering Sciences Research Group, Department of Mechanical Engineering, School of Engineering, Faculty of Engineering and Physical Sciences, University of Southampton, SO17 1BJ, UK.
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Mendis HC, Ozcan A, Santra S, De La Fuente L. A novel Zn chelate (TSOL) that moves systemically in citrus plants inhibits growth and biofilm formation of bacterial pathogens. PLoS One 2019; 14:e0218900. [PMID: 31233560 PMCID: PMC6590827 DOI: 10.1371/journal.pone.0218900] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 06/11/2019] [Indexed: 11/19/2022] Open
Abstract
Ternary solution (TSOL) is a novel Zn chelate-based systemic antimicrobial formulation designed for treating citrus bacterial pathogens 'Candidatus Liberibacter asiaticus' and Xanthomonas citri subsp. citri. TSOL is a component of MS3T, a novel multifunctional surface/sub-surface/systemic therapeutic formulation. Antimicrobial activity of TSOL was compared with the antimicrobial compound ZnO against X. citri subsp. citri and 'Ca. L. asiaticus' surrogate Liberibacter crescens in batch cultures. X. citri subsp. citri and L. crescens were also introduced into microfluidic chambers, and the inhibitory action of TSOL against biofilm formation was evaluated. The minimum inhibitory concentration of TSOL for both X. citri subsp. citri and L. crescens was 40ppm. TSOL was bactericidal to X. citri subsp. citri and L. crescens above 150 ppm and 200 ppm, respectively. On the contrary, ZnO was more effective as a bactericidal agent against L. crescens than X. citri subsp. citri. TSOL was more effective in controlling growth and biofilm formation of X. citri subsp. citri in batch cultures compared to ZnO. Time-lapse video imaging microscopy showed that biofilm formation of X. citri subsp. citri was inhibited in microfluidic chambers treated with 60 ppm TSOL. TSOL also inhibited further growth of already formed X. citri subsp. citri and L. crescens biofilms in microfluidic chambers. Leaf spraying of TSOL showed higher plant uptake and systemic movement in citrus (Citrus reshni) plants compared to that of ZnO, suggesting that TSOL is a promising antimicrobial compound to control vascular plant pathogens such as 'Ca. L. asiaticus'.
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Affiliation(s)
- Hajeewaka C. Mendis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States of America
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States of America
| | - Ali Ozcan
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States of America
- Department of Chemistry, University of Central Florida, Orlando, FL, United States of America
| | - Swadeshmukul Santra
- NanoScience Technology Center, University of Central Florida, Orlando, FL, United States of America
- Department of Chemistry, University of Central Florida, Orlando, FL, United States of America
- Department of Materials Science and Engineering, University of Central Florida, Orlando, FL, United States of America
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL, United States of America
| | - Leonardo De La Fuente
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States of America
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