Decimal place slope, a fast and precise method for quantifying 13C incorporation levels for detecting the metabolic activity of microbial species

*both authors contributed equally Abbreviations: 1-D – one dimensional, 2-DE – two-dimensional gel electrophoresis, CID-collision-induced dissociation, Da – Dalton, DNA – deoxyribonucleic acid, ESI- electrospray ionization, FT-ICR- fourier transform ion cyclotron resonance, HISH-SIMS- halogen in situ hybridization-secondary ion mass spectroscopy, HDPR- half decimal place rule, LC- liquid chromatography, LTQ- linear trap quadrupole, MALDI- matrix-assisted laser desorption/ionization, MS – mass spectrometry, m/z – mass-to-charge ratio, SIP – stable isotope probing, SDS-PAGE- sodium dodecyl sulfate-polyacrylamide gel electrophoresis, TCA