Application of MALDI-TOF mass spectrometry to the identification of endophytic bacterial communities associated with plants

FLORENCIA ALVAREZ; JOSÉ LUIS LÓPEZ; ANTONIO LAGARES

Córdoba

Congreso; XI Congreso Argentino de Microbiología General (SAMIGE); 2015

SAMIGE-Asociación Civil de Micobiología General

In the last years, matrix-assisted laser-desorption/ionizationtime of flight mass spectrometry (MALDI-TOFMS) has been increasingly used for the identification of microorganisms. Mainlyribosomal and housekeeping proteins contribute to the signals in a typicalwhole-cell mass spectrum, which explains the species-specific conservation of peakswith coincident m/z ratios (evenamong samples grown under different cultivation conditions). The advantageous ofthe technique -such as simple handling, speed of processing,cost-effectiveness, and high-throughput capabilities, among others- havepositioned the MS profiling of bacterial extracts as a highly convenient typingmethod over other more traditional approaches (i.e. biochemical typing, rDNA sequencing).In the present study we have expanded the application of MALDI-TOF MS analysis tothe characterization of the bacterial diversity present in communitiesassociated with plants, specifically bacteria that interact with varieties of Medicago sativa (alfalfa). Good qualityspectra were collected from the main bacterial species present in alfalfaplants (seeds, roots, aerial part), which had been previously isolated in ourlaboratory and identified based on the partial sequencing of their corresponding16S rDNA. The collected spectra from the plant-associated bacteria includeddata for more than 25 different genera and were used to expand the MALDI Biotyperdatabase (Bruker Daltonics). Interestingly, the MALDI-TOF-based analysisallowed in some cases the distinction between isolates of a same bacterialspecies. We are now using MS typing to characterize the relative abundance ofbacterial species in different plant niches to characterize their specific microbiomes.Contrasting with classical population analyses based on PCR of bulk 16S rDNAand high-throughput sequencing, the new approach -based on a clone-by-clone analysis-also allows for the preservation of individual clones of interest for their furtherbiological characterization.