Metabolomic analysis of Trichoderma spent media
To evaluate if the overall differences in rhizobial strains response toTrichoderma 1W spent media could be related to the presence of
species-specific differences in metabolite composition, a gas
chromatography-mass spectrometry (GC-MS) analysis of theTrichoderma spp. 1W spent media was performed. The GC-MS
profiling detected a total of 987 peaks (Supplementary Dataset
S1 ), 76 of which could be identified (cut-off >80% of
identification probability). These mainly belong to aromatic, cyclic and
aliphatic hydrocarbons, carboxylic acids, alcohols, esters, sugars and
their derivatives, terpenes and their derivatives.
Spent media were mainly composed by 2H-Pyran-2-one, 6-pentyl- (a
representative metabolite common to the Trichoderma genus),
1-Monopalmitin, a compound known for having activity against pathogenic
organisms , and succinic acid, monoethyl ester. The peak area of these
and of the other compounds varied among samples (seeSupplementary Dataset S1, worksheet 2 ). Principal component
analysis (PCA) (Figure 2 ) indicated strong differences inT. gamsii and T. harzianum spent media, while T.
tomentosum and T. velutinum were more similar. The biplot
analysis showed that differences in 2H-Pyran-2-one, 6-pentyl- quantities
were associated with T. gamsii vs. the other fungi. T.
tomentosum profiles were related to differences in 1-Monopalmitin.
Other compounds contributing to the main differences were Hexadecane and
Octadecanoic acid, 2,3-bis[(trimethylsilyl)oxy]propyl ester.T. velutinum spent medium profiles were associated with
differences for 1-Monopalmitin, and succinic acid, monoethyl ester. The
compound 2,3,4,5,6-Pentahydroxyhexanal was associated with T.
harzianum spent medium. It is worth noting that the difference betweenT. gamsii and T. tomentosum/T. velutinum highlighted in
the biplot is in good agreement with the phenotypic differences observed
in the overall panel of rhizobial strain (Figure 1 ), suggesting
that possibly some of the compounds mentioned above may target rhizobial
metabolism, giving rise to contrasting bacterial responses.