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Alkenones are unique lipids produced by certain species of microalgae, well-known for use in paleoclimatology, and more recently pursued to advance sustainability across multiple industries. Beginning in 2018, the biosynthesis of alkenones by commercially grown Tisochrysis lutea ( T - Iso ) microalgae from one of the world's most established producers, Necton S.A., changed dramatically from structures containing 37 and 38 carbons, to unusual shorter-chain C35 and C36 diunsaturated alkenones (C35:2 and C36:2 alkenones). While the exact reasons for this change remain unknown, analysis of alkenones isolated from T-Iso grown in 2021 and 2023 revealed that this change has persisted. The structure of these rare shorter-chain alkenones, including double bond position, produced by Necton T-Iso remained the same over the last five years, which was determined using a new and optimized cross-metathesis derivatization approach with analysis by comprehensive two-dimensional gas chromatography and NMR. However, noticeable differences in the alkenone profiles among the different batches were observed. Combined with fatty acid compositional analysis, the data suggest a connection between these lipid classes ( e.g. , increased DHA corresponds to lower amounts of shorter-chain alkenones) and the ability to manipulate their biosynthesis in T-Iso with changes to cultivation conditions., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The bloom-forming cyanobacteria Trichodesmium contribute up to 30% to the total fixed nitrogen in the global oceans and thereby drive substantial productivity. On an expedition in the Gulf of Mexico, we observed and sampled surface slicks, some of which included dense blooms of Trichodesmium erythraeum . These bloom samples contained abundant and atypical free fatty acids, identified here as 2-methyldecanoic acid and 2-methyldodecanoic acid. The high abundance and unusual branching pattern of these compounds suggest that they may play a specific role in this globally important organism., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)