Even simple invertebrates can tell beneficial bacteria apart from harmful ones with surprising precision, according to new research from Heinrich Heine University Düsseldorf and Kiel University in Germany.
The study focused on the sea anemone Nematostella vectensis, whose immune system can selectively distinguish helpful microbes from dangerous ones using structures called nematosomes — motile, multicellular bodies that patrol for bacteria. Scientists had long assumed that only vertebrates, with their adaptive immune systems, were capable of this level of microbial discrimination.
Lead author Dr. Nida Kaya and senior author Professor Sebastian Fraune found that a gene called cJun controls how nematosomes function. When the researchers used CRISPR to knock out cJun, the sea anemones produced fewer nematosomes, lost their ability to discriminate between bacteria, developed imbalanced microbiomes, and became more susceptible to infection.
The findings add to a growing body of evidence for “trained immunity” — a form of innate immune memory — in organisms that predate the evolution of adaptive immunity, suggesting the roots of sophisticated microbial recognition run deeper in the animal family tree than previously understood.
Journal: Nature Communications
Article Title: “c-JUN controls microbial colonization via selective phagocytosis in the sea anemone Nematostella”
DOI: 10.1038/s41467-026-75511-w
Publication Date: 10-Jul-2026
Source: EurekAlert