Bacterial strains collections, screening

The screening of natural products became highly popular following the discovery of penicillin from a mould. Plants, fungi, and bacterial strains were collected from all round the world in an effort to find other metabolites with useful biological activities. This led in particular to an impressive arsenal of antibacterial agents (Chapter 9). Screening of natural products from plant and microbial sources continues today in... 

Bacterial diversity is estimated to cover more than four million different taxa based on 16S RNA gene differences (Curtis, Sloan, Scannell, 2(X)2) and reflects adaptation to a wide variety of environments, including such diverse habitats as water, air, soil, the human body, food, etc. Each species is comprised of a multitude of individual strains with unique properties. Due to this large diversity, screening of the total microbial population for any desired phenotype or property is unrealistic, and so screening is normally limited to a collection of bacteria obtained fiom certain relevant habitats. Bioremediation applications could start with a collection of bacteria isolated from soil dairy tqtplications, a collection derived from environmoits were milk is present, and so on. In addition, the ability to isolate and identify individual bacterial strains with specific desirable properties requires not only microbiological expertise but also highly automated processes. 

Intact-cell MALDI-TOF analysis offers several attractive features for rapid screening of bacterial collections. Analysis is performed directly on the cells after minimal sample preparation, and data acquisition is complete in only a matter of minutes. Intact biomarkers are introduced into the MALDI-TOF instrument under these conditions. Whether the observed biomarker molecules are desorbed directly from the surface of the cell wall or are extracted from the cells and co-crystallized with the matrix is currently unresolved, but MALDI spectra of intact bacteria generally contain a large number of peaks in the mass range 1-20 kDa [31]. For bacterial cells, proteins are the most often observed biomarkers. While this approach samples only a small percentage of the total proteins produced in the cells, these profiles have been reported by many groups to be suitable for taxonomic identification, down to at least the strain level. The wide availability of the MALDI-TOF instrumentation and its relative ease of use, coupled with relatively simple sample preparation procedures, have been key features in the rapid advancement of this approach. 

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