The Plasmid pEX18Gm Indirectly Increases Caenorhabditis elegans Fecundity by Accelerating Bacterial Methionine Synthesis

Plasmids are mostly found in bacteria as extrachromosomal genetic elements and are widely used in genetic engineering. Exploring the mechanisms of plasmid–host interaction can provide crucial information for the application of plasmids in genetic engineering. However, many studies have generally focused on the influence of plasmids on their bacterial hosts, and the effects of plasmids on bacteria-feeding animals have not been explored in detail. Here, we use a “plasmid–bacteria–Caenorhabditis elegans” model to explore the impact of plasmids on their host bacteria and bacterivorous nematodes. First, the phenotypic responses ofC. eleganswere observed by feedingEscherichia coliOP50 harboring different types of plasmids. We found thatE. coliOP50 harboring plasmid pEX18Gm unexpectedly increases the fecundity ofC. elegans. Subsequently, we found that the plasmid pEX18Gm indirectly affectsC. elegansfecundity via bacterial metabolism. To explore the underlying regulatory mechanism, we performed bacterial RNA sequencing and performed in-depth analysis. We demonstrated that the plasmid pEX18Gm upregulates the transcription of methionine synthase genemetHin the bacteria, which results in an increase in methionine that supportsC. elegansfecundity. Additionally, we found that a pEX18Gm-induced increase inC. eleganscan occur in different bacterial species. Our findings highlight the plasmid–bacteria–C. elegansmodel to reveal the mechanism of plasmids’ effects on their host and provide a new pattern for systematically studying the interaction between plasmids and multi-species.Keywords:plasmid–host interaction;bacteria;C. elegans;fecundity;multi-species;RNA-seq;methionine;HPLC-MS/MS