23841
Since their inception in the 1970s , methods for classification of microorganisms based on mass spectral fingerprints obtained by MALDI - TOF MS have become a mainstay in environmental as well as in clinical microbiology .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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