Evidence on antimicrobial properties and mode of action of a chitosan obtained from crustacean exoskeletons on Pseudomonas syringae pv. tomato DC3000

Abstract

Pseudomonas syringae pv. tomato DC3000 (Pto DC3000) causes bacterial speck of tomato, a widely spread disease that causes significant economical losses worldwide. It is representative of many bacterial plant diseases for which effective controls are still needed. Despite the antimicrobial properties of chitosan has been previously described in phytopathogenic fungi, its action on bacteria is still poorly explored. In this work, we report that the chitosan isolated from shrimp exoskeletons (70 kDa and 78 % deacetylation degree) exerts cell damage on Pto DC3000. Chitosan inhibited Pto DC3000 bacterial growth depending on its concentration, medium-pH, and presence of metal ion (Mg(+2)). Biochemical and cellular changes resulting in cell aggregation and impaired bacterial growth were also viewed. In vivo studies using fluorescent probes showed cell aggregation, increase in membrane permeability, and cell death, suggesting the chitosan antibacterial activity is due to its interaction as a polycation with Pto DC3000 membranes. Transmission electron microscopic analysis revealed that chitosan also caused morphological changes and damage in bacterial surfaces. Also, the disease incidence in tomato inoculated with Pto DC3000 was significantly reduced in chitosan pretreated seedlings, revealing a promising action of chitosan as nontoxic biopesticide in tomato plants. Indeed, a wider comprehensive knowledge of the mechanism of action of chitosan in phytopathogenic bacterial cells will increase the chances of its successful application to the control of spread disease in plants.

Chitosan antimicrobial and eliciting properties for pest control in agriculture: a review

“…tomato DC3000 decreased 50 % compared with control. However, the addition of MgCl 2 rescued the values of the chitosan-treated group (Mansilla et al 2013). The addition of Mg 2+ or Ca 2+ increased the concentration of positive charges in the system and weakened the bacteriostatic action that mainly depends on electrostatic forces.…”

“…2, pretreatment of tomato seedlings with 10 μg/mL chitosan before Pseudomonas syringae pv. tomato DC3000 (Pto DC3000) inoculation significantly decreased bacterial damages in cotyledons compared with control (Mansilla et al 2013). Not only does chitosan inhibit planktonic cell growth but also it affects the already established biofilms.…”

“…As a versatile material, chitosan exhibits proved antimicrobial activities against fungi, bacteria, and viruses and acts as an elicitor of plant defense mechanisms. With the wide-spectrum antimicrobial activities, chitosan has been utilized to reduce or prevent the spread of pathogens (Li et al 2013a;Mansilla et al 2013;Fig. 2) or to enhance plant innate immunity defenses (El-Ghaouth et al 1994;Amborabé et al 2008;Fondevilla and Rubiales 2012).…”

Insights into epidemiology and control of diseases of annual plants caused by the Pseudomonas syringae species complex

“…Chitosan is applied against a range of plant pathogens including strains in the Pssc. Pretreatment of tomato seedlings with chitosan before P. syringae inoculation markedly reduced bacterial damage in cotyledons compared with a control (Mansilla et al 2013). Moreover, chitosan has been reported to affect already established biofilms.…”

Novel antimicrobial chitosan–cellulose composite films bioconjugated with silver nanoparticles

“…Moreover, the outer membrane of Gram-negative bacteria such as E. coli consists of lipopolysaccharides (LPS) containing phosphate and pyrophosphate groups which make the cell surface negatively charged (Prescott et al, 2002). The cell wall can attach to chitosan by electrostatic interaction, more adsorbed chitosan would evidently result in greater changes in the structure and permeability of the cell membrane (Tripathi et al, 2011;Alishahi et al, 2012;Mansilla et al, 2013). The grampositive bacteria also have a thicker and more regid peptidoglycan cell wall (Shirvan et al, 2014).…”