Which group of organisms produces Saxitoxin?

• A. Fungi
• B. Bacteria
• C. Marine and freshwater algae and cyanobacteria
• D. Plants

Answer: (C)

Saxitoxin is produced by certain aquatic microorganisms, specifically marine and freshwater algae and cyanobacteria. In practice, this includes dinoflagellates (marine and some freshwater algae) and cyanobacteria (blue-green algae) that form harmful algal blooms. The toxin blocks voltage-gated sodium channels in nerve and muscle cells, preventing action potentials and leading to paralysis, which is why it causes paralytic shellfish poisoning when contaminated shellfish are eaten. Fungi, plants, and most bacteria do not produce saxitoxin.