Gc grade hexane

Bacterial membrane proteins were removed with the help of Proteinase K for efficient extraction of membrane lipids. The bacteria were grown as described earlier and the cell pellet was collected. The cells were washed twice with PBS buffer (pH 7.4) and resuspended in PBS buffer (0.5 g in 0.5 mL). Proteinase K (25 μg/mL, Sigma-Aldrich, St. Louis, MO) was added to the cell suspension in presence of 5 mM dithiothreitol and incubated for 30 min at 37°C. An aliquot (100 μL) of protease-inhibitor solution was added to stop the protease activity. The protease-inhibitor solution was prepared by dissolving a tablet of EDTA-free protease inhibitor (cOmplete, Roche Applied Science, Penzberg, Germany) in 10 mL of PBS (pH 7.4). The mixture was then centrifuged (4,000 × g, 10 min, 4°C) to collect the cell pellet (0.5 g wet weight) for extraction of FA. Membrane FA were extracted and converted to FAME, as described by Sasser (1990) . Decanoic acid (C10:0) was used as the internal standard and was added to the cell pellet before extraction and methylation. The ex-tracted FA were concentrated by drying under nitrogen and redissolved in GC-grade hexane (Fisher Scientific, Pittsburgh, PA) before analysis.