Planktonins

Planktonins are a proposed class of bioactive small molecules associated with marine plankton. The term does not refer to a single compound but to structurally related metabolites observed across diverse planktonic organisms, including phytoplankton and some zooplankton. The concept arose from metabolomic studies of seawater and plankton communities.

Structurally, planktonins show considerable diversity, with motifs that resemble polyketide-derived backbones and peptide-like fragments. Biosynthetic pathways are not fully resolved; evidence supports involvement of both native plankton biosynthetic genes and symbiotic bacteria that supply precursors or enzymes. The resulting molecules vary in polarity and size, complicating extraction and identification.

Ecologically, planktonins are detected in coastal and open-ocean samples at typically low concentrations. They are implicated in chemical signaling among plankton, deterring grazers, and shaping microbial interactions by modulating bacterial communities or viral activity. Blooms and environmental conditions can influence production, suggesting a role in dynamic trophic coupling within the planktonic food web.

Detection and structural characterization rely on high-resolution mass spectrometry, nuclear magnetic resonance, and chromatographic separation. Because many planktonins occur at trace levels in complex matrices, robust isolation is challenging, and some proposed structures await confirmation. Researchers continue to search for standardized nomenclature and well-supported biosynthetic models.

Significance and prospects: planktonins represent a growing area in marine natural products and chemical ecology. While promising for understanding plankton interactions and potential pharmacological properties, the field remains exploratory, with ongoing debates about prevalence, ecological impact, and practical applications.