GCRIS

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Molecular Investigation of Pathogenic Bacteria in the Presence of Phenolic Acids
(Izmir Institute of Technology, 2019) Özdemir, Özgün Öykü; Soyer, Ferda
Pathogenic bacteria, including P. aeruginosa, are serious threats for human health with their antibiotic resistance and virulence factors. Since phenolic acids, secondary metabolites of plants, can be good candidates as antimicrobial agents, their mode of action should be investigated. Proteomics is one of the main approaches for elucidating the mode of action of such compounds. In addition, in order to enhance the antimicrobial effects and stabilities of phenolics, they can be encapsulated into nanoparticles. The nanoparticles can be produced from chitosan and alginate which are biocompatible polymers. In this study, the antimicrobial effects of 3-HPAA and 4-HBA were presented with MIC values of 2.1 and 1.9 mg/ml, respectively. The bacteriocidal effects of them were also shown as 2.3 mg/ml for 3-HPAA and 2.1 mg/ml for 4-HBA. The morphological changes of bacteria were determined after phenolic acid exposure via SEM. The LC-ESI-MS/MS technique was used to show changes in the protein profile of bacteria arose from antimicrobial effects. Both phenolic exposures resulted in various protein changes especially in membrane-related proteins as well as ribosome and protein synthesis related-proteins. In addition, they caused serious oxidative stress depending on the protein profile changes related to redox proteins. Alginate-chitosan nanoparticles resulted increased antimicrobial effects of the phenolics which were produced, characterized and tested on various pathogenic bacteria via agar diffussion and spectrophotometric measurements. Hence, free or encapsulated forms of phenolic acids were demonstrated as effective antimicrobial agents and based on proteomic results, the effect of phenolic acids may be multi targetted.
Investigation of Molecular Effect of Phenolic Acids on Methicillin-Resistant and Methicillin-Susceptible Staphylococcus Aureus in Comparison To Their Phenolic Acid Resistant Mutants
(Izmir Institute of Technology, 2018) Keman, Deniz; Soyer, Ferda
Staphylococcus aureus is a Gram-positive bacterium whose acquisition through an open wound results in various infections. Methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains are responsible for diseases ranging from soft tissue infections to fatal pneumonia which cannot be treated due to multiple drug-resistances of these strains. This situation increases the importance of searching for alternative antimicrobials worldwide. Having all these in mind, the capacity of phenolic acids cannot be denied to be used against pathogenic bacteria. Phenolic acids produced as plant secondary metabolites show antibacterial effects besides many beneficial properties for human health. The aim of this study was to investigate the antibacterial action mechanisms of vanillic acid and 2-hydroxycinnamic acid on MRSA and MSSA. To achieve this, firstly the antibacterial effects of phenolic acids on both bacteria were investigated by determination of minimum inhibitory concentrations. Then, the resistance development ability of bacteria against phenolic acids was tested by continuous exposure to subinhibitory concentrations. Finally, the action mechanisms of phenolic acids on bacteria were elucidated using two different proteomic approaches. According to the results, bacteria were not able to develop resistance against phenolic acids. Proteomic studies displayed alterations in the protein profiles of phenolic acid treated bacteria and provided potential targets in the battle with pathogenic bacteria. By showing the inability of MRSA and MSSA to develop resistance to phenolic acids and the important proteomic alterations that are induced by phenolic acid treatment, this study highlights the significance of phenolic acids to be used against antibiotic-resistant bacteria.

Phd Degree / Doktora

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