Microorganisms by Pyrolytic Techniques

Among analytical techniques, the pyrolytic procedures can be applied for microorganism identification due to their sensitivity, need for a minute amount of sample, applicability to a wide range of microorganisms, and the relatively short time required for analysis [1]. Several problems are related to the use of pyrolytic techniques for microorganism characterization. Some are related to sample preparation and are not specific to pyrolytic procedures, while others are related to the pyrolytic technique itself. 

Besides whole microorganisms that were analyzed by pyrolytic techniques, a variety of preparates were also subject to this type of analysis. Cell walls, capsular extracts or other specific extracts were the subject of pyrolytic analyses. Significant differences can be seen between different preparates, and this imposes another requirement for pyrolytic analysis with taxonomic purposes. The reproducibility of the technique for obtaining the preparates must be very good in order to avoid sample contamination with unwanted cell components. 

The pyrolytic process is commonly used for microorganism analysis coupled with GC, GC/MS, or direct MS. The variability and sources of errors in Py-GC, Py-MS, or Py-GC/MS in general were previously discussed (see Sections 5.2, 5.3, and 5.4). Several problems regarding sample loading, pyrolysis temperature control, analytical instrument sensitivity, etc. should be considered regarding this part of the analysis. Among these three techniques, Py-MS is probably the most utilized as it provides rapid results and requires a minute amount of sample even compared to the other pyrolytic techniques. 

As indicated previously, the structural information from Py-MS studies is not straightfonward, but for fingerprinting the samples it is adequate. 

Phospholipids, which are responsible for the structure of the cell membrane, are easily accessed through simple extraction procedures providing a useful biomarker for microbial detection and identification. However, they are influenced by the growth conditions, nutritional status, and history of a microorganism. These factors cause changes in the phospholipid (phosphoglyceride) profile as the microbe changes its membrane composition in response to its environmental requirements. 

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