title: Precision and sensitivity of the measurement of 15N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry.
abstract: Sensitive detection of cellular components from specific groups of microbes can be utilized as 'signatures' in the examination of microbial consortia from soils, sediments or biofilms.  Utilizing capillary gas chromatography/mass spectrometry and stereospecific derivatizing agents, D-alanine, a component localized in the prokaryotic (bacterial) cell wall, can be detected reproducibly.  Enrichments of D-[15N]alanine determined in E. coli grown with [15N]ammonia can be determined with precision at 1.0 atom%.  Chemical ionization with methane gas and the detection of negative ions (M - HF)- and (M - F or M + H - HF)- formed from the heptafluorobutyryl D-2 butanol ester of D-alanine allowed as little as 8 pg (90 fmol) to be detected reproducibly.  This method can be utilized to define the metabolic activity in terms of 15N incorporation at the level of 10(3)-10(4) cells, as a function of the 15N-14N ratio.
authors.affiliation: Laboratory of Ecological Chemistry, University of Lund, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Tunlid
authors.forename: G
authors.initials: G
authors.lastname: Odham
authors.forename: R H
authors.initials: RH
authors.lastname: Findlay
authors.forename: D C
authors.initials: DC
authors.lastname: White
mesh_terms: D000409:Alanine / Q000032:analysis* / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry; D002849:Chromatography, Gas; D004783:Environmental Microbiology; D004926:Escherichia coli; D013058:Mass Spectrometry; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism; D009587:Nitrogen Isotopes
chemical_list: D009587:Nitrogen Isotopes; D009584:Nitrogen; D000409:Alanine