Hewlett Packard (Agilent Technologies) Gas Chromatograph with Mass Selective Detector and Flame Ionization Detector Microbial Identification System (MIDI, Inc.)

A Hewlett-Packard 5890A gas chromatograph with a HP 5971A mass selective and flame ionization detectors, autosampler, and HP 3365 Series II ChemStation software and Wiley/NBS database library are available in the Multi-User Analytical laboratory. The HP gas chromatograph is also set up with microbial identification software (MIDI, Inc.) utilizing a flame ionization detector for fatty acid analysis. The system is connected to a personal computer and LaserJet printer.
The MIDI Microbial Identification System (MIS) brings reference laboratory results into the routine laboratory. The MIS automates microbial identification by combining the time-proven identification technique of cellular fatty acid analysis with computerized high resolution gas chromatography. The computer controlled chromatographic system automatically determines the fatty acid compositions of unknown isolates based on standards, then searches an extensive libraries of known compositions for a match to give an accurate species identification. Cellular fatty acid composition is a very stable genetic trait which is highly conserved. Standardized growth conditions are used for most species reducing temperature and media variability. Presently there are libraries for aerobic and anaerobic bacteria, yeast and a few medically important fungi. Research is presently being conducted on the analysis and identification of plant pathogenic fungi using fatty acid profiles. Research is also being conducted on the usage of the system in the analysis of microbial communities by extracting fatty acids directly from soil without any growth of bacteria. Software associated with the MIDI system allows for 2-D principle component cluster analysis and development of dedrograms of specific samples.

The mass selective detector system has a Wiley database of over 160,000 spectra associated with it for comparison of mass spectra from unknown samples to those in the library. The gas chromatograph is set up with capillary columns with split/splitless injectors. The microbial identification component is set up specifically with an Ultra 2, 25 m x 0.25 mm, 0.33 µ film column. Various capillary columns can be associated with the mass selective detector system.