JMSSJ On-line, Vol. 55 (2007) No. 3, pp. 209-216
Rapid Classification and Identification of Bacteria by Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Using Ribosomal Proteins as Biomarkers
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    Kanae TERAMOTO, Hiroaki SATO,* Liwei SUN, Masaki TORIMURA, and Hiroaki TAO

    Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, IBARAKI, JAPAN

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is beginning to play an important role in rapid identification and classification of industrially useful or pathogenic bacteria. Instead of conventional mass spectral fingerprint approaches, MALDI-MS identification of bacteria using ca. 50 ribosomal subunit proteins as biomarkers has been proposed. In this bioinformatics-based method, the masses of ribosomal subunit proteins in bacterial lysates observed by MALDI-MS are compared with the calculated masses predicted from the amino acid sequences registered on protein databases such as Swiss-Prot. Therefore, taxonomic identification of bacteria at species level would be ideally performed. Considering the possible mismatch between the actual and calculated masses of the biomarkers, we further developed a highly reliable method applicable to bacterial classification at strain level by detailed characterization of expressed ribosomal subunit proteins of several bacteria. With our developed method using a verified mass list of expressed ribosomal proteins of genome-sequenced strains as a reference, bacterial samples isolated from soil could be successfully classified at strain level. As an application, detection of cross-contamination of culture collections was also described.

Key words: MALDI-MS, Bacteria, Ribosomal protein, Classification, Protein database

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