The Catenulida flatworm can express genes from its microbiome or from the DNA it ingests

Stenostomum are tiny planarians of the phylum Platyhelminthes that reproduce asexually. We transfected these worms using plasmids containing a gfp reporter gene. Here we show that they can express genes present in plasmids carried by bacteria and those that are encoded by naked DNA, such as plasmids or PCR fragments, transfected by electroporation; they can also express genes taken up during feeding. The microbiome associated with worm maintenance was evaluated, and the results indicated that when a plasmid is maintained in the microbiome, gfp gene expression is stable. When genes originate from naked DNA or bacteria not maintained in the microbiome, GFP expression is transient. Therefore, changes in the microbiome can modify the ability of worms to express foreign genes. In stable GFP-expressing worms, NSG showed that the gfp gene was maintained in the plasmid and was not integrated into the chromosome. These results suggest that, at least for some organisms such as flatworms, the expression of genes provided by the microbiome or the environment can be considered among the potential sources of phenotypic plasticity, which can have implications for evolvability.