Cymbopogon nardus Essential Oil as Protein Inducer in Bacillus subtilis ATCC21332
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 α 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.