Fatty acid fingerprint (MIDI)

Cellular fatty acids are analysed after conversion into fatty acid methyl esters (FAMEs) by saponification, methylation and extraction using minor modifications of the method of Miller (1982) and Kuykendall et al., (1988). The fatty acid methyl esters mixtures are separated by gas chromatography and detected by a flame ionisation detector using Sherlock Microbial Identification System (MIS) (MIDI, Microbial ID, Newark, DE 19711 U.S.A.). Peaks are automatically integrated and fatty acid names and percentages calculated by the MIS Standard Software (Microbial ID). 

The identification of the fatty acids included in the accompanying report are based on the various peak naming tables supplied by MIDI Inc (Newark, USA) as part of their Sherlock Microbial Identification System. Different peak naming tables have been developed over the years and may be specific for certain groups of organisms. 

Required material: For the analysis of the cellular fatty acids an active growing culture or 30 mg freeze dried cells is required.

Dr. Susanne Verbarg

Additional information

The DSMZ supplies the fatty acid reports without further comment or interpretation and it is the responsibility of the customer to interpret the results in a fashion relevant to the organism they have supplied. Most peak naming tables use the “omega” (ω) nomenclature for identifying the position of unsaturation, numbering from the methyl end of the fatty acid. However, this is not always the case and the alternative nomenclature for numbering the position of unsaturation from the carboxyl end has also been used both in the Sherlock system as well as in the literature. The DSMZ uses an Agilent 6890N gas chromatograph and version 6.1 of the MIDI Inc Sherlock MIS software. The software version appears at the bottom left hand corner of the reports. The method of preparation of the samples is the standard method given in MIDI Technical Note 101 (and in the handbook). The database used to identify the fatty acids is given on the report sent to you.

Useful links provided by MIDI Inc.

References

  1. Kuykendall, L.D., Roy, M.A., O'Neill, J.J., Devine, T.E. 1988. Fatty acids, antibiotic resistance, and deoxyribonucleic acid homology groups of Bradyrhizobium japonicum. International Journal of Systematic Bacteriology 38:358-361.
  2. Miller, L.T. 1982. A single derivatization method for bacterial fatty acid methyl esters including hydroxy acids. Journal of Clinical Microbiology 16:584-586.