Isolation and Purification of Low Molecular Weight Proteins from Liquid Culture for Mycobacterium Tuberculosis by Chromatography

Tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium tuberculosis. M. tuberculosis has different molecular weight secreted antigens. Low molecular weight proteins secreted into the culture medium by M. tuberculosis are thought to play an important role in the development new TB diagnostic tests and new vaccines against tuberculosis. In this report, we describe isolation and purification of low-molecular-weight proteins secreted by M. tuberculosis. Initially by biphasic medium, bacteria from Lowenstein-Jensen solid medium transferred to a Dorset-Henley liquid medium and After 6 weeks of growth, the bacteria with a 0.22 micron filters of liquid medium containing secreted proteins were isolated and the secreted proteins was precipitated by ammonium sulfate. Protein concentrations were determined by using the lowry protein assay. Then low molecular weight proteins were purified by Sephadex-G75 gel chromatography and we studied purification of low molecular weight proteins by Coomassie-Blue stained SDS-PAGE. The results showed that low molecular weight secreted proteins purified from M. tuberculosis strain DT. Also, low molecular weight proteins made up approximately 65.3% of total proteins. this study demonstrated that without break down of bacteria bodies can be purified low molecular weight secreted proteins from M. tuberculosis liquid medium by Sephadex-G75 gel chromatography.