Exploring Intra- and Inter-Species Horizontal RNA Transfer (HRT) in Bacillus subtilis as a possible mode of microbial communication.

In nature, bacteria live in complex multicellular communities called biofilms, in which cells communicate to coordinate their activity. Bacterial communication through small molecules has been extensively studied. In recent years, there is growing evidence of macromolecule exchange between bacterial cells. RNA is highly dynamic and can be both functional and informational, as it represents an accurate state of the cells recent history and, theoretically, can be propagated or inserted to the genome by reverse-transcription.

We show that RNA can be transferred both within and between species. When grown in a co-culture, we detected RNA molecules originating from B. subtilis, B. simplex, and E. coli “donors” in a B. subtilis “acceptor“. The RNA transfer was mostly mediated by membrane vesicles. Interestingly, the transferred RNAs detected in the donor were enriched for stable, non-coding RNAs.

Ongoing research will decipher the mechanisms of the HRT. First, by performing a real-time follow-up of specific confirmed-as-transferred molecules using MS2 tagging. second, a bioinformatic analysis the RNA content of membrane vesicles vs. both the “donor” transcriptome, and the “donor” RNA found in the “acceptor“, will test the specificity of the RNA transferred is different environmental conditions, such as antibiotic stress. Moreover, we evaluate the fitness contribution of HRT by measuring the survival rate of the “acceptor” in antibiotic stress conditions: (1) with or without the presence of “donor” vesicles, and (2) with an inducible allele in the “acceptor” of promising confirmed-as-transferred RNAs. Overall, we believe that this research will reveal a new cell-cell communication mechanism in bacteria.