Bacteria and fungi wield toxins in ways once thought unique to snakes and scorpions, according to a new study from Loma Linda University School of Medicine. Traditionally, venom has been defined as a biological toxin delivered through a wound by specialized structures such as fangs or stingers. This work shows that reliance on venom-like strategies for predation, defense and competition is far more widespread than previously thought.
“Venomous animals have long fascinated biologists that were seeking to understand their deadly secretions and the traits associated with their use, but have also contributed numerous life-saving therapeutics,” the lead author William K. Hayes said. “Until now, our understanding of venom, venom delivery systems, and venomous organisms has been based entirely on animals, which represents only a tiny fraction of the organisms from which we could search for meaningful tools and cures.”
In the plant world, toxins are injected through spines, thorns and stinging hairs. Some species even farm ants as living weapons—providing shelter and food in exchange for protection. These interactions mirror the specialized delivery systems of venomous animals.
Fungi, too, have evolved penetration structures. Beyond the familiar hyphal filaments, some fungi develop independent organs that pierce host tissues to introduce toxic compounds. This apparatus functions much like a microscopic harpoon.
Bacteria deploy molecular syringes. Their secretion systems and contractile injection devices force toxins directly through cell membranes and into host tissues, inflicting damage akin to a snakebite. These mechanisms can target both animal and plant cells.
Certain protists discharge harpoon-like extrusomes called toxicysts and nematocysts. These organelles penetrate prey cells and deliver potent toxins in a single, swift action. This strategy is a clear parallel to the stingers of jellyfish.
Even viruses can behave like venomous agents. Bacteriophages inject nucleic acids and virion proteins into host cells, wreaking havoc comparable to conventional venoms. Though not always classified as “true” organisms, their injection systems are functionally analogous.
Toxins have traditionally been grouped as poisons, toxungens and venoms based on how they enter other organisms. This study reveals that wound-based delivery—what we call venom—is a convergent solution across bacteria, fungi, protists, plants and viruses. Recognizing these parallels expands our view of evolutionary innovation.
Hayes hopes this broader perspective will spark new collaborations across disciplines. “We’ve only scratched the surface in understanding the evolutionary pathways of venom divergence, which include gene duplication, co-option of existing genes, and natural selection,” he said.
By applying the same frameworks used to study animal venoms to non-animal systems, researchers may uncover novel bioactive compounds and delivery mechanisms with therapeutic potential. It’s a reminder that, in biology, the most remarkable innovations often arise in unexpected places.
The study has been published in MDPI Toxins.
