Abstract
Curcumin is a natural dietary compound with antimicrobial activity against various gram positive and negative bacteria. This study aims to investigate the proteome level alterations in Bacillus subtilis due to curcumin treatment and identification of its molecular/cellular targets to understand the mechanism of action. We have performed a comprehensive proteomic analysis of B. subtilis AH75 strain at different time intervals of curcumin treatment (20, 60 and 120 min after the drug exposure, three replicates) to compare the protein expression profiles using two complementary quantitative proteomic techniques, 2D-DIGE and iTRAQ. To the best of our knowledge, this is the first comprehensive longitudinal investigation describing the effect of curcumin treatment on B. subtilis proteome. The proteomics analysis revealed several interesting targets such UDP-N-acetylglucosamine 1-carboxyvinyltransferase 1, putative septation protein SpoVG and ATP-dependent Clp protease proteolytic subunit. Further, in silico pathway analysis using DAVID and KOBAS has revealed modulation of pathways related to the fatty acid metabolism and cell wall synthesis, which are crucial for cell viability. Our findings revealed that curcumin treatment lead to inhibition of the cell wall and fatty acid synthesis in addition to differential expression of many crucial proteins involved in modulation of bacterial metabolism. Findings obtained from proteomics analysis were further validated using 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) assay for respiratory activity, resazurin assay for metabolic activity and membrane integrity assay by potassium and inorganic phosphate leakage measurement. The gene expression analysis of selected cell wall biosynthesis enzymes has strengthened the proteomics findings and indicated the major effect of curcumin on cell division.
Highlights
In spite of worldwide initiatives for the development of a plethora of synthetic and semi-synthetic drugs, emerging drug resistance is still remained as one of the foremost health problems and poses challenges for thriving combat against most of the pathogenic infections [1]
The growth of the cells treated with 20 μM of curcumin (IC50) was significantly declined; whereas cultures treated with 100μM of curcumin (MIC) showed virtually no growth compared to the untreated controls, clearly indicating the antibacterial activity of curcumin against B. subtilis (Figs 1A and S1A)
Quite a few earlier studies have investigated the effect of curcumin on B. subtilis, the mechanism of action of the drug and its role in filamentation as well as exact molecular targets are still unclear and proteome level analysis has not been performed hitherto
Summary
In spite of worldwide initiatives for the development of a plethora of synthetic and semi-synthetic drugs, emerging drug resistance is still remained as one of the foremost health problems and poses challenges for thriving combat against most of the pathogenic infections [1]. B. subtilis is a widely studied non-pathogenic gram-positive bacterium, which is often used as a model organism for diverse cellular and molecular level studies due to its genetic amenability, availability of complete genome sequence, and easy isolation and culturing procedure. Chemically known as 1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene3,5-dione, is a naturally occurring phytochemical obtained from the rhizome of Curcuma longa. It is the polyphenolic traditional turmeric powder, which is widely used as a dietary component. Curcumin possess anti-microbial activity against gram positive and negative bacteria and shows synergetic effects on other drugs in combination therapies [11]. The diverse therapeutic potential of curcumin has been established, its precise mechanism of action and molecular targets in prokaryotic system are mostly obscure. Another study indicates that curcumin can effectively perturb the FtsZ assembly dynamics leading to elongation of the bacterial cell length and reduce the viability [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
