Microorganisms species, identification

With the polymerase chain reaction (PCR), a few molecules of any DNA sequence can be multiplied by a factor of 10 to 10 in a very short time. The sequence is multiplied in a highly specific way until it becomes visible electrophoretically. Based on PCR, analytical techniques have been developed for species identification in the case of animal and plant foods and microorganisms. It is... 

The capability to identify an intact protein by deducing its partial amino acid sequence (a sequence tag) in a Fourier transform ion cyclotron resonance (FTICR) MS/MS experiment and subsequent homology search in a proteome database was first demonstrated by Mortz et al. [38]. In analogy to bottom-up proteomics, unambiguous identification of one or more intact protein biomarkers by top-down proteomics allows successful microorganism identification (provided the proteome database contains both the respective protein sequences and the respective organism sources). Top-down proteomics approaches for Bacillus spore protein biomarkers and from there Bacillus species identification have been also described [27,45]. For instance, biomarker proteins from Bacillus cereus T spores have been analyzed... 

Kennedy, M.J. and Thakur, M.S. (1993) The use of neural networks to aid in microorganism identification a case study of Haemophilus species identification. Antonie van Leeuwenhoek, 63 35—38. 

Multiply charged proteins can also be partially sequenced, and microsequences of proteins isolated from several microorganisms have been reported, accomplished with electrospray ionization and FTMS.23,90 Nonadjacent fragment ions may be used to identify bacterial proteins in these top-down strategies.91 In all cases these sequences could be related by bioinformatics to the parent species. An obvious extension would be to characterize proteins from intact microorganisms in this way. In at least one instance a microsequence has been obtained from a protein released from a contaminated intact bacteriophage sample (MS2) to provide a chemotaxonomic identification.77 This work was carried out in an ion trap mass spectrometer. 

Recently a number of more sophisticated methods for identification of microorganisms have been developed. However, alongside their increase in accuracy and complexity their cost has also risen. Widespread biochemical methods of identification are rather labour intensive and the results obtained are not always reliable due to the high variability of microbial species. 

A contaminated container should be examined carefully for any breach in the container system. All positives (from integral containers) should be identified to at least genus and to species whenever possible. The identification of contaminant should be compared to the database of the organisms recently identified. The biochemical profile of the contaminant can then be compared to that of microorganisms obtained from the sterility tests and bioburden and environmental monitoring programs, in order to help identify the potential sources of the contaminant. 

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