Use of earthworm casts to validate FT-IR spectroscopy as a ‘sentinel’ technology for high-throughput monitoring of global changes in microbial ecology

This study aimed to evaluate metabolic fingerprinting by Fourier transform infrared (FT-IR) spectroscopy as a technique for investigating microbial communities and their activities in soil. FT-IR spectra from earthworm casts, and other ‘biosamples’, were compared using multivariate cluster analyses. The work formed part of a wider study to quantify the risk of horizontal gene flow and to assess ecological impacts associated with the release of GM crops or recombinant micro-organisms. A range of samples, including pure cultures of similar soil bacteria, plant materials and earthworm casts of various ages and feeding regimes were analysed. A subset of the cast FT-IR data was compared with DGGE analysis of extracted DNA/RNA. Cluster analysis of FT-IR spectra was capable of differentiating between different bacterial, litter and cast samples. There was congruence between FT-IR and DGGE clustering for food type but not for cast age. Further detailed work on the microbial populations will be needed to investigate relationships between microbial and spectroscopy data.