Novel cyanobacterial strains modulate morphophysiological traits of Lemna trisulca: Insights from short- and...

Cyanobacteria produce a diverse array of bioactive secondary metabolites, encompassing both harmful and potentially beneficial compounds. This study evaluated the effects of five cyanobacterial strains with uncharacterized metabolomes, including the new species Komarekiella chia, Nodularia mediterranea, and Iphianassa zackieohae-on Lemna trisulca plant. Both short-term (exposure of plant to cyanobacterial extracts for 24 h) and long-term (2-week co-cultivation) experiments were conducted. In short-term assays, Jaaginema sp. extract transiently inhibited photosynthesis within 7 min, while all extracts produced an increase in respiration after 24 h. Ultrastructural analysis revealed that co-cultivation with Jaaginema sp. and Trichormus variabilis resulted in chloroplast membrane abnormalities and absence of starch grains. K. chia and N. mediterranea induced distinct ultrastructural modifications, whereas I. zackieohae caused only minimal changes. During the long-term experiments, co-cultivation with I. zackieohae initially stimulated plant growth, although this was not sustained after 14 days. The remaining strains caused a slight inhibition of biomass accumulation. Notably, long-term exposure to K. chia and N. mediterranea led to increases in plant protein content by 33 % and 44 %, respectively. Only I. zackieohae did not affect chlorophylls content, while other strains reduced chlorophyll a and b by 48 % and 53 %, respectively. Reactive oxygen species imaging revealed no signs of oxidative stress during either exposure period. Finally, HPLC/MS-MS analyses ruled out the common cyanotoxins anatoxin-a, cylindrospermopsin, and microcystin-LR production in all tested strains. These findings identify promising candidate species for further investigation of novel bioactive metabolites and underscore the need for additional studies to elucidate plant-cyanobacteria interactions.