Evidence of nitro-fatty acids in microscopic algae and cyanobacteria

Nitro-fatty acids (NO 2 FAs) are pleiotropic cell signalling modulators, playing a role in stress responses, development, and defence mechanisms in many organisms, including plants. However, to date their production in photosynthetic microorganism has not been studied. In this study, using LC-MS analysis, we first evaluated the ability of the green algae Desmodesmus communis, D. subspicatus and Chlorella sp., cyanobacterium Synechocystis sp., and eustigmatophyte Trachydiscus minutus to produce NO 2 FAs. It was found that the studied strains are able to produce precursor oleic acid (OA), linoleic acid (LA) and its conjugated version (cLA), as well as arachidonic acid (AA) and also stearic acid (SA). Simultaneously, we demonstrated the production of NO 2 OA in Synechocystis sp. and D. subspicatus , and also NO 2 SA in Chlorella sp. and T. minutus based on LC-MS analysis with NO 2 FA ultrapure regio/stereoisomeric standards. The levels of NO 2 OA and NO 2 SA were more than 1000 times lower than the level of non-nitrated FAs. These results show that freshwater algae and cyanobacteria are capable of producing saturated and unsaturated NO 2 FAs. The detailed distribution of NO 2 FAs and their function in other algae and cyanobacteria species should be clarified in the future.