The inhibitory effect of a non-yessotoxin-producing dinoflagellate, Lingulodinium polyedrum (Stein) Dodge, towards Vibrio vulnificus and Staphylococcus aureus.

The increased bacterial resistance to antibiotics has caused global concern, prompting the search for new compounds. Because of their abundance and diversity, marine phytoplankton are an important potential source of such compounds. Research on dinoflagellates has led to the discovery of inhibitors of bacterial growth. The marine dinoflagellate Lingulodinium polyedrum blooms in different regions of the world, including Mexico, and is also known to regulate the growth of other species in coastal waters. Here, we investigated the taxonomy of this dinoflagellate and characterized the ability of its extracts to inhibit the growth of two bacteria of medical importance (Vibrio vulnificus and Staphylococcus aureus). Taxonomic characterization was performed by PCR and gene amplification of ITS, and confirmed that the species isolated off the Pacific coast of Mexico was L. polyedrum. To prove the inhibitory effect of L. polyedrum extracts, cultures were harvested by centrifugation. Pellets from three cellular abundances were extracted with water, methanol, hexane and chloroform. The experiments on V. vulnificus showed a high growth inhibition for the four extracts, ranging from 77 to 98 %. Surprisingly, the growth inhibition was lower when the extracts originated from a higher L. polyedrum cell abundance, ranging from 0 to 34 %. For S. aureus, the growth inhibition was also high, but not statistically different for all extracts and cell abundances, ranging from 62 to 99 %. This study obtained promising results for future pharmacological applications. Our Mexican strain of L. polyedrum did not produce any detectable yessotoxins.