Rapid analysis of intact phospholipids from whole bacterial cells by matrix‐assisted laser desorption/ionization mass spectrometry combined with on‐probe sample pretreatment

Abstract

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), utilizing an on-probe sample pretreatment, was applied to the rapid and direct detection of intact phospholipids from whole bacterial cells. The sample preparation procedure involved depositing growing bacterial colonies from culture dishes directly onto the MALDI probe followed by treatment of the sample spot with a 3 micro L aliquot of an aqueous 0.05 M solution of sodium iodide prior to the addition of a 2,5-dihydroxybenzoic acid (DHB) matrix solution (ca. 8 mg dissolved in 70% acetonitrile/30% H(2)O containing 0.1% of trifluoroacetic acid). The MALDI spectra obtained from whole bacteria cells showed a series of ions generated from bacterial phospholipids, such as phosphatidylethanol-amines (PEs) and phosphatidylglycerols (PGs), which were clearly observed as well-resolved peaks. The ranges of the observed total carbon numbers in two acyl groups for PEs and PGs (30-36 and 33-36, respectively) were in good agreement with those reported previously. Furthermore, the distinct discrimination of four species of the Enterobacteriaceae family cultured identically was achieved by using principal components analysis (PCA) conducted on the relative peak intensities of phospholipids observed from the MALDI spectra.

Rapid lipid profiling of bacteria by online MALDI-TOF mass spectrometry

“…The experimental results show that the mass spectra obtained with chloroform/methanol as the extraction solvent present more mass peaks. The lipid profiles of the bacteria obtained in the experiment are basically consistent with previously reported profiles obtained using the traditional MALDI methods [15,36,38,39].…”

“…MALDI have been applied to analyze lipid extracts or lipids in whole cell bacteria [14][15][16][17].…”

Lipid fingerprinting of Bacillus spp. using online MALDI-TOF mass spectrometry

“…33 MALDI-TOF MS has also been applied to obtain abundant, accurate mass ion signals of the phospholipids in bacteria. [34][35][36][37][38][39] Therefore, the characterization of lipids in bacteria and other microorganisms plays a crucial role for taxonomic identification, differentiation of pathogenic species, and understanding of metabolic processes under normal or stressed growth conditions. However, there are few reports on the application of online MALDI-TOF MS coupling with lipid profiling for identification of bacterial species.…”

Mass spectrometry: a revolution in clinical microbiology?

“…The 2,5-dihydroxybenzoic acid (DHB) allows the formation of long crystals from the periphery to the center of the deposit. It is suitable for a majority of taxons and requires more laser shots to obtain 100 to 200 peaks per spectrum and many signals whose the m/z is > 10 kDa [18] . The manipulation of this matrix is trickier.…”