title: Detection of fatty acids from intact microorganisms by molecular beam static secondary ion mass spectrometry.
abstract: We report the use of a surface analysis approach, static secondary ion mass spectrometry (SIMS) equipped with a molecular (ReO(4)(-)) ion primary beam, to analyze the surface of intact microbial cells. SIMS spectra of 28 microorganisms were compared to fatty acid profiles determined by gas chromatographic analysis of transesterfied fatty acids extracted from the same organisms. The results indicate that surface bombardment using the molecular primary beam cleaved the ester linkage characteristic of bacteria at the glycerophosphate backbone of the phospholipid components of the cell membrane. This cleavage enables direct detection of the fatty acid conjugate base of intact microorganisms by static SIMS. The limit of detection for this approach is approximately 10(7) bacterial cells/cm(2). Multivariate statistical methods were applied in a graded approach to the SIMS microbial data. The results showed that the full data set could initially be statistically grouped based upon major differences in biochemical composition of the cell wall. The gram-positive bacteria were further statistically analyzed, followed by final analysis of a specific bacterial genus that was successfully grouped by species. Additionally, the use of SIMS to detect microbes on mineral surfaces is demonstrated by an analysis of Shewanella oneidensis on crushed hematite. The results of this study provide evidence for the potential of static SIMS to rapidly detect bacterial species based on ion fragments originating from cell membrane lipids directly from sample surfaces.
authors.affiliation: Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls 83415-2208, USA. jani.ingram@nau.edu
authors.forename: Jani C
authors.initials: JC
authors.lastname: Ingram
authors.forename: William F
authors.initials: WF
authors.lastname: Bauer
authors.forename: R Michael
authors.initials: RM
authors.lastname: Lehman
authors.forename: Sean P
authors.initials: SP
authors.lastname: O'Connell
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Shaw
mesh_terms: D001419:Bacteria / Q000737:chemistry* / Q000145:classification / Q000302:isolation & purification; D005227:Fatty Acids / Q000032:analysis* / Q000145:classification / Q000302:isolation & purification; D008958:Models, Molecular; D010712:Phosphatidic Acids / Q000032:analysis / Q000145:classification; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*
chemical_list: D005227:Fatty Acids; D010712:Phosphatidic Acids