Abstract
BackgroundWe describe a new approach to the recovery of information from faecal samples, based on the analysis of the molecular signature generated by rapid evaporative ionisation mass spectrometry (REIMS).ResultsFaecal pellets from five different rodent species were analysed by REIMS, and complex mass spectra were acquired rapidly (typically a few seconds per sample). The uninterpreted mass spectra (signatures) were then used to seed linear discriminant analysis and classification models based on random forests. It was possible to classify each species of origin with a high rate of accuracy, whether faeces were from animals maintained under standard laboratory conditions or wild-caught. REIMS signatures were stable to prior storage of the faecal material under a range of different conditions and were not altered rapidly or radically by changes in diet. Further, within species, REIMS signatures could be used to discriminate faeces from adult versus juvenile mice, male versus female mice and those from three different laboratory strains.ConclusionsREIMS offers a completely novel method for the rapid analysis of faecal samples, extending faecal analysis (previously focused on DNA) to an assessment of phenotype, and has considerable potential as a new tool in the armamentarium of the field biologist.
Highlights
Faeces are a common ‘calling card’ left by animals in the wild, and such deposits have proven to be a valuable source of information regarding species [1, 2], sex [3], diet [4] and physiological status, notably stress hormone metabolites [5]
The relatively new technique of rapid evaporative ionisation mass spectrometry (REIMS) provides a new potential method for the analysis of information contained in faeces
Faecal samples generate informative REIMS data A typical rodent faecal pellet was, after hydration, able to conduct electricity and burn rapidly during REIMS acquisition (Fig. 1b; a video file of the burn process is given in Additional file 1: Video S1)
Summary
Faeces are a common ‘calling card’ left by animals in the wild, and such deposits have proven to be a valuable source of information regarding species [1, 2], sex [3], diet [4] and physiological status, notably stress hormone metabolites [5]. There is a scope for novel approaches to faecal analysis to supplement and support such methods, especially for new methods that are rapid and applied. One of the major areas of development in biological mass spectrometry has been the development of new ambient ion sources that permit mass spectral data to be collected without prior sample preparation [11,12,13]. The relatively new technique of rapid evaporative ionisation mass spectrometry (REIMS) provides a new potential method for the analysis of information contained in faeces. The molecules are subjected to ‘soft’ ionisation that generates information-rich molecular ions [14]. We describe a new approach to the recovery of information from faecal samples, based on the analysis of the molecular signature generated by rapid evaporative ionisation mass spectrometry (REIMS)
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