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Abstract
Betaine lipids (BL) from ten microalgae species of the kingdoms Plantae and Chromista
were identified and quantified by HPLC/ESI-TOF-MS. Diacylgyceryl-N-trimethylhomoserine
(DGTS) was detected in Trebouxiophyceae and Eustigmatophyceae species, whereas Tetraselmis
suecica was described as the first green algae containing diacylglyceryl-hydroxymethyl-N,N,N-trimethyl-beta-alanine
(DGTA). DGTA molecular species where also characterized in Cryptophyceae species as
well as in the Bacillariophyceae diatom Phaeodactylum tricornutum. The Mediophyceae
diatom Chaetoceros gracilis had no DGTA, but contained diacylglyceryl-carboxyhydroxymethylcholine
(DGCC). A principal coordinate (PCO) analysis of microalgae species revealed the existence
of three main clusters around each BL type. The first PCO axis (43.9% of total variation)
grouped Chlorophyceae, Trebouxiophyceae and Eustigmatophyceae species and positively
correlated with DGTS. The second PCO axis (27.8% of total variation) segregated DGTA
from DGCC containing species. Cryptophyceae, Bacillariophyceae and Chlorodendrophyceae
were the more closely associated species to DGTA. Mediophyceae and Dinophyceae species
contained DGCC as the only BL. Molecular diversity varied from the simplest DGCC composition
in Gyrodinium dorsum to the highest spectrum of ten different molecular species detected
for DGTA (Rhodomonas baltica) and DGCC (C. gracilis). The fatty acid profile of DGTS
was very dissimilar to that of the whole lipid cell content. DGTS from Nannochloropsis
gaditana was highly unsaturated respecting to total lipids, whereas in Picochlorum
atomus DGTS unsaturation was nearly one half to that of total lipids. Dissimilarity
between DGTA and total lipid fatty acid profile was minimum among all BL and DGTA
fatty acid unsaturation was the maximum observed in the study. New DGCC molecular
species enriched in 20:5 were described in Mediophyceae diatoms. Multivariate microalgae
ordination using BL as descriptors revealed a higher chemotaxonomic potential than
that based on their respective BL fatty acid profile. Nevertheless, taxonomic resolution
was improved when fatty acids from the whole cell lipid pool were used.