Precision and sensitivity of the measurement of 15 N enrichment in D-alanine from bacterial cell walls using positive/negative ion mass spectrometry

• 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 (bacteria) cell wall, can be detected reproducibly. Enrichments of D- 15 N]alanine determined in E. coli grown with [ 15 N]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 15 N incorporation at the level of 10 3 -10 4 cells, as a function of the 15 N- 14 N ratio.

Ämnesord

NATURVETENSKAP  -- Kemi -- Analytisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Analytical Chemistry (hsv//eng)

Nyckelord

Bacterial cell wall

Capillary gas chromatography/mass spectrometry

D-Alanine

Positive/negative ion chemical ionization

Selected ion monitoring

Stable isotope labeling

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