Proteins levels produced by bacteria may be increased in stressful surroundings, such as in the presence of antibiotics. It appears that many antimicrobial agents or antibiotics, when used at low concentrations, have in common the ability to activate or repress gene transcription, which is distinct from their inhibitory effect. There have been comparatively few studies on the potential of antibiotics or natural compounds in nature as a specific chemical signal that can trigger a variety of biological functions. Therefore, this study was focusing on the effect of essential oil from Cymbopogon flexuosus in regulating proteins production by Bacillus subtilis ATCC21332. The Minimum Inhibition Concentration (MIC) of the C. flexuosus essential oil on B. subtilis was determined by using microdilution assay, resulting 1.76mg/ml. The bacteria cells were further exposed to the C. flexuosus essential oil at concentration of 0.01 MIC for 72 h. The proteins were then isolated and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Proteins profile showed that a band with approximate size of 30 kDa was appeared for the treated bacteria with C. flexuosus essential oil. Thus, B. subtilis ATCC21332 in stressful condition with the presence of C. flexuosus essential oils at low concentration could induce the protein production. The isolated protein also showed antimicrobial activity against selected Gram-positive and Gram-negative bacteria.
Protein production by bacteria might be increased in stressful conditions such as in the presence of antimicrobial agents. Many studies proved that antibiotics or antimicrobial agents at low concentration are able to activate or repress gene transcription process in bacteria. However, there are still few studies on potential of natural antimicrobial compounds such as Cymbopogon essential oils acting as specific chemical signal that can trigger biological functions of bacteria. Therefore, this study aims to explore the potential of natural antimicrobial compound (Cymbopogon flexuosus and Cymbopogon nardus) at low concentration in regulating proteins production by Lactobacillus plantarum ATCC8014. The bacteria cells of L. plantarum ATCC8014 are exposed to Cymbopogon essential oils at low concentration in fermentation process for 48 hours at 37°C. SDS-PAGE analysis showed that a new intracellular protein with approximate size of 40 kDa was produced by L. plantarum ATCC8014 after being enhanced with C. nardus essential oil. Besides, the intracellular proteins, each with approximate size of 85 kDa, 45 kDa and 28 kDa synthesized by L. plantarum ATCC8014 prior to inducing with C. nardus or C. flexuosus were expressed differently. Some of the intracellular proteins were highly expressed and some of the proteins were repressed based on the intensity of protein bands appeared. Hence, L. plantarum ATCC8014 in the presence of Cymbopogon essential oils at low concentration could regulate the intracellular proteins production. The isolated protein also showed antimicrobial activity against selected Gram-positive and Gram-negative bacteria.
Combination effects between Cymbopogon flexuosus and Cymbopogon nardus essential oils were studied to determine whether the combination could emerge as better and more powerful antimicrobial agents against six selected bacteria includes Bacillus subtilis, Escherichia coli, Salmonella typhimurium, Serratia marcescens, Staphylococcus aureus, and Staphylococcus epidermidis. This combination study exhibited 40.67% additive, 28.67% antagonistic, 16.00% indifferent and 14.66% synergistic effects. C. flexuosus and C. nardus essential oils in combination showed a high inhibitory activity against S. aureus with 16% synergistic, 64% additive and 20% indifferent effects.
Protein production by bacteria might be increased in stressful conditions such as in the presence of antimicrobial agents. Many studies have proven that antibiotics or antimicrobial agents at low concentration are able to activate or repress gene transcription process in bacteria. However, there have been comparatively few studies on the potential of natural compounds in nature as a specific chemical signal that can trigger a variety of biological functions. An attempt was made to study the effect of essential oil from Cymbopogon nardus in regulating protein production by Bacillus subtilis ATCC21332. The bacterial cells were further exposed to the C. nardus essential oil at concentration of 0.02 % for 48 h at 37°C. The intracellular proteins were then isolated and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Proteins profile showed that a band with approximate size of 180 kDa appeared for the treated bacteria with C. nardus essential oil. An alignment of peptide sequences to the NCBI BLAST database revealed that B. subtilis ATCC21332 in stressful condition tend to produce intracellular protein recognized as respiratory nitrate reductase ? subunit enzyme. Besides, the extracellular proteins secreted by B. subtilis ATCC21332 after being subjected to 0.02% of C. nardus essential oil for 48 and 72 h at 30°C, were further analyzed on antimicrobial activity. The extracellular proteins secreted by B. subtilis ATCC21332 prior to enhancing with 0.02 % C. nardus essential oil at 30°C for 72 h exhibited antimicrobial activity towards two strains of bacteria, which are Bacillus cereus and Escherichia coli.
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