title: Differentiation of spores of Bacillus subtilis grown in different media by elemental characterization using time-of-flight secondary ion mass spectrometry.
abstract: We demonstrate the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) in a forensics application to distinguish Bacillus subtilis spores grown in various media based on the elemental signatures of the spores. Triplicate cultures grown in each of four different media were analyzed to obtain TOF-SIMS signatures comprised of 16 elemental intensities. Analysis of variance was unable to distinguish growth medium types based on 40Ca-normalized signatures of any single normalized element. Principal component analysis proved successful in separating the spores into groups consistent with the media in which they were prepared. Confusion matrices constructed using nearest-neighbor classification of the PCA scores confirmed the predictive utility of TOF-SIMS elemental signatures in identifying sporulation medium. Theoretical calculations based on the number and density of spores in an analysis area indicate an analytical sample size of about 1 ng, making this technique an attractive method for bioforensics applications.
authors.affiliation: Advanced Radioanalytical Chemistry, National Security Directorate, Pacific Northwest National Laboratory, MS P7-07, P.O. Box 999, Battelle Blvd., Richland, WA 99352, USA. john.cliff@pnl.gov
authors.forename: John B
authors.initials: JB
authors.lastname: Cliff
authors.forename: Kristin H
authors.initials: KH
authors.lastname: Jarman
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Valentine
authors.forename: Steven L
authors.initials: SL
authors.lastname: Golledge
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Gaspar
authors.forename: David S
authors.initials: DS
authors.lastname: Wunschel
authors.forename: Karen L
authors.initials: KL
authors.lastname: Wahl
mesh_terms: D001412:Bacillus subtilis / Q000737:chemistry / Q000145:classification / Q000254:growth & development / Q000502:physiology; D015373:Bacterial Typing Techniques; D002127:Calcium Isotopes / Q000032:analysis*; D003470:Culture Media; D004602:Elements; D044707:Forensic Sciences / Q000379:methods; D007554:Isotopes / Q000032:analysis; D008855:Microscopy, Electron, Scanning; D025341:Principal Component Analysis; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*; D013171:Spores, Bacterial / Q000737:chemistry / Q000145:classification / Q000254:growth & development / Q000502:physiology
chemical_list: D002127:Calcium Isotopes; D003470:Culture Media; D004602:Elements; D007554:Isotopes