Antimicrobial action of t-cinnamaldehyde on Escherichia coli MG1655
Antimicrobial resistance pose a global thread nowadays. Compounds of natural origin are an important source of drugs used in clinical practice. However, it is important to understand both their principles of efficacy and their molecular mechanism of action. In this study we evaluated antimicrobial potential of t-cinnamaldehyde which is an organic compound found in many plant species, especially in the Cinnamomum genus, such as Cinnamomum zeylanicum and cassia. Cinnamon oil extracted from the bark of these plants contains up to 80% trans-cinnamaldehyde. Although CNMA has shown antimicrobial properties against numerous Gram+ and Gram- species, its mode of action against pathogens remains not fuly elucidated. Therefore, this project aims to determine CNMA activity at the level of gene expression. Total RNA was isolated and checked for quality using the Bioanalyzer 2100. The sequencing run was conducted on the Illumina NovaSeq6000 platform. 30 million pair-end reads per samples were assessed with 101 pb read length. Reference E. coli MG1655 genome sequence and annotations were downloaded from GenBank. Differentially expressed analysis of 0.25 x MIC CNMA was performed against untreated control in indicated time with p = 0.001 and log2FC = 1.5. We have discovered many changes bacterial transcriptome. For instance: following the treatment with 0.25×MIC of CNMA, we found 292 and 140 upregulated and 107 and 96 downregulated genes at time points 30 and 60?min, respectively. Among the most enriched genes, were those related to the tricarboxylic acid (TCA) cycle, flagellum synthesis, amino acid transport, and oxidoreductase activity. According to these findings we can conclude that observed transcriprional pattern indicates severe metabolic downshift in treated cells, and consequently activation of stress processes. These was in line with our secondary experiments which revealed drop in growth kinnetic, cytoplasm shrinkage, NAD/NADH level alteration and elevation of stringent response alarmones ((p)ppGpp). Taken together, this suggests that CNMA-treated E. coli bacteria undergo major metabolic changes that finally result in cell death. Overall design: To obtain a overview of the impact of t-cinnamaldehyde (CNMA) on bacterial fitness, we analyzed the transcriptome changes in cells treated with sub-inhibitory concentration (0.25xMIC). Total RNA sequencing was performed to assess the changes in gene expression pattern at 30 and 60 min post t-cinnamaldehyde treatment. Experiment was performed in three independent repeats, untreated cultures where used as a control.