Proteomic Analyses Reveal New Insights on the Antimicrobial Mechanisms of Chitosan Biopolymers and Their Nanosized Particles against Escherichia coli

Abstract

The well-known antimicrobial effects of chitosan (CS) polymers make them a promising adjuvant in enhancing antibiotic effectiveness against human pathogens. However, molecular CS antimicrobial mechanisms remain unclear, despite the insights presented in the literature. Thus, the aim of the present study was to depict the molecular effects implicated in the interaction of low or medium molecular mass CS polymers and their nanoparticle-counterparts against Escherichia coli. The differential E. coli proteomes sensitized to either CS polymers or nanoparticles were investigated by nano liquid chromatography-mass spectrometry (micro-LC-MS/MS). A total of 127 proteins differentially expressed in CS-sensitized bacteria were predominantly involved in (i) structural functions associated to the stability of outer membrane, (ii) increment of protein biosynthesis due to high abundance of ribosomal proteins and (iii) activation of biosynthesis of amino acid and purine metabolism pathways. Antibacterial activity of CS polymers/nanoparticles seems to be triggered by the outer bacterial membrane disassembly, leading to increased protein biosynthesis by diverting the metabolic flux to amino acid and purine nucleotides supply. Understanding CS-antibacterial molecular effects can be valuable to optimize the use of CS-based nanomaterials in food decontamination, and may represent a breakthrough on CS nanocapsules-drug delivery devices for novel antibiotics, as the chitosan-disassembly of bacteria cell membranes can potentialize antibiotic effects.Chitosan antimicrobial activity has already been explored on many levels, since it was discovered that its polymers or nanoparticles are effective against Gram positive and Gram negative bacterial strains, including antibiotic-resistant pathogens [5]. In addition, CS has been widely used to carry antibiotic and antimicrobial compounds, such as peptides. In this context, it can serve as a versatile vehicle for the intracellular delivery of therapeutic agents, and is also useful as a non-viral vector for gene delivery [2].Previous studies have suggested various mechanisms to explain the mode of action leading to chitosan antimicrobial activity [6][7][8].The most explored is the intracellular leakage hypothesis, where bacterial membrane permeability is altered by the interaction between positively-charged-CS and negatively-charged bacterial surfaces, resulting in the loss of cytosolic components through the damaged plasma membrane, leading to cell death [6]. This theory was reinforced by studies investigating CS microparticles, interactions with specific targets hypothesized to be the surface-exposed proteins. Furthermore, it has been demonstrated that CS microparticles likely bind to the outer membrane protein OmpA by hydrogen bonding, and to lipopolysaccharides (LPS) via ionic interaction killing the bacteria [9]. In addition, CS antimicrobial activity has been observed, not only in acidic pH, but also at neutral pH (i.e., 7.0) [10].In a previous study, CS nanoparticles produced by polymer ul...

Seafood Waste as Attractive Source of Chitin and Chitosan Production and Their Applications

“…Other factors related to chitosan antimicrobial activity are the absorbing property of metal ions and their ease of penetrating the cell wall and binding to DNA, inhibiting messenger RNA synthesis, and low molecular weight of chitosan molecule induced inhibition of DNA transcription and mRNA synthesis in E. coli [ 110 , 111 , 112 , 113 , 114 , 115 ].…”

Chitosans and Nanochitosans: Recent Advances in Skin Protection, Regeneration, and Repair

“…Low-molecular-weight chitosan oligomers pass through the cell membrane and alter cell permeability [37]. Nanochitosans have been shown to disassemble bacteria cell membranes and inhibit metabolic and biosynthetic pathways [38].…”

“…Resveratrol owes its antioxidant activity to its phenolic hydroxyl groups and can be used to achieve oxidative skin cell homeostasis following topic use or aid in the fight against chronic and degenerative human physiopathological conditions by promoting organism oxidative balance when administered systemically as a nutraceutical or pharmaceutical [43]. Chitosans also exhibit well-documented antimicrobial activities against Gram-positive and Gram-negative bacteria and fungi [38,53]. However, due to its low solubility, antimicrobial activity is limited to acidic media, although antimicrobial activity in neutral media can be improved by transforming amino groups into quaternary ammonium salts (NR4 + X − ) [54].…”

“…Chitosans also exhibit well-documented antimicrobial activities against Gram-positive and Gram-negative bacteria and fungi [38,53]. However, due to its low solubility, antimicrobial activity is limited to acidic media, although antimicrobial activity in neutral media can be improved by transforming amino groups into quaternary ammonium salts (NR4 + X − ) [54].…”

Preparation and Evaluation of the Antibacterial Effect of Chitosan Nanoparticles Containing Ginger Extract Tailored by Central Composite Design

“…14,15 Studies have shown that chitosan binding to lipopolysaccharides on the bacterial surface disrupts the order of the bacterial membrane and causes the plasma to leak out. 16 It also increases the chances of drug penetration into the bacterial cytoplasm. 17 In this study, aqueous and methanolic extracts were obtained from ginger root individually, and then CHI nanoparticles (NPs) containing each extract were prepared.…”