title: Comprehensive assignment of mass spectral signatures from individual Bacillus atrophaeus spores in matrix-free laser desorption/ionization bioaerosol mass spectrometry.
abstract: We have fully characterized the mass spectral signatures of individual Bacillus atrophaeus spores obtained using matrix-free laser desorption/ionization bioaerosol mass spectrometry (BAMS). Mass spectra of spores grown in unlabeled, 13C-labeled, and 15N-labeled growth media were used to determine the number of carbon and nitrogen atoms associated with each mass peak observed in mass spectra from positive and negative ions. To determine the parent ion structure associated with fragment ion peaks, the fragmentation patterns of several chemical standards were independently determined. Our results confirm prior assignments of dipicolinic acid, amino acids, and calcium complex ions made in the spore mass spectra. The identities of several previously unidentified mass peaks, key to the recognition of Bacillus spores by BAMS, have also been revealed. Specifically, a set of fragment peaks in the negative polarity is shown to be consistent with the fragmentation pattern of purine nucleobase-containing compounds. The identity of m/z = +74, a marker peak that helps discriminate B. atrophaeus from Bacillus thuringiensis spores grown in rich media is [N1C4H12]+. A probable precursor molecule for the [N1C4H12]+ ion observed in spore spectra is trimethylglycine (+N(CH3)3CH2COOH), which produces a m/z = +74 peak when ionized in the presence of dipicolinic acid. A clear assignment of all the mass peaks in the spectra from bacterial spores, as presented in this work, establishes their relationship to the spore chemical composition and facilitates the evaluation of the robustness of "marker" peaks. This is especially relevant for peaks that have been used to discriminate Bacillus spore species, B. thuringiensis and B. atrophaeus, in our previous studies.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Abneesh
authors.initials: A
authors.lastname: Srivastava
authors.forename: Maurice E
authors.initials: ME
authors.lastname: Pitesky
authors.forename: Paul T
authors.initials: PT
authors.lastname: Steele
authors.forename: Herbert J
authors.initials: HJ
authors.lastname: Tobias
authors.forename: David P
authors.initials: DP
authors.lastname: Fergenson
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Horn
authors.forename: Scott C
authors.initials: SC
authors.lastname: Russell
authors.forename: Gregg A
authors.initials: GA
authors.lastname: Czerwieniec
authors.forename: Carlito B
authors.initials: CB
authors.lastname: Lebrilla
authors.forename: Eric E
authors.initials: EE
authors.lastname: Gard
authors.forename: Matthias
authors.initials: M
authors.lastname: Frank
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001412:Bacillus subtilis / Q000737:chemistry* / Q000254:growth & development; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000254:growth & development; D017610:Calcium Compounds / Q000032:analysis; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D003470:Culture Media; D007553:Isotope Labeling; D009587:Nitrogen Isotopes; D010848:Picolinic Acids / Q000032:analysis; D011687:Purines / Q000032:analysis / Q000737:chemistry; D012521:Sarcosine / Q000032:analysis; D013045:Species Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013171:Spores, Bacterial / Q000737:chemistry* / Q000254:growth & development
chemical_list: D000596:Amino Acids; D017610:Calcium Compounds; D002250:Carbon Radioisotopes; D003470:Culture Media; D009587:Nitrogen Isotopes; D010848:Picolinic Acids; D011687:Purines; C004860:dipicolinic acid; D012521:Sarcosine