Fig. 1.

Discriminant function analysis (DFA) for sample visualization (uncontrolled contamination). GC-MS metabolite data successfully distinguished samples from contaminated versus noncontaminated microalgal flasks. Projections of the log-transformed intracellular metabolite data from 36 samples into three-dimensional (3D) space show two very distinct clusters of the two data classes (contaminated versus noncontaminated). For each sample, the projection values were calculated as the linear combination of metabolite values determined by DFA. Only metabolites that were detected in more than 25% of the samples for each data class were used for the analysis. Black, samples from contaminated flasks (time [t] = 24 to t = 96 h); dark gray, samples from noncontaminated flaks (t = 24 to t = 96 h); light gray, samples from contaminated flasks at time zero.