Inhibition of VSV by Extracellular RNA from Culture Filtrate of Lactobacillus DM8909 in Vitro

Abstract

Extracellular nucleic acids were found in the culture filtrate of Lactobacillus DM8909 at exponential growth phase. The study focused on the source, characteristics, nucleotide sequence and biological functions of extracellular nucleic acids in Lactobacillus DM8909. Nucleic acids in the culture filtrate were proven to be RNA by agarose gel electrophoresis which closely paralleled bacterial growth. Different experimental procedures (according to viral infection course) to assay the potential antiviral activity of RNA were used. Cell survival and viral inhibition were determined by antiviral assay and confirmed by immunofluorescence. Results showed the “excess” extracellular RNA which could inhibit viral infection to the host cells in vitro.The “excess” extracellular RNA may be excreted from Lactobacillus DM8909. The possible mechanisms of antiviral activity include: 1) interfering virus attachment or entry into the cells, perhaps by steric hindrance; 2) conducting as a signaling molecule in the cross-talk between probiotics and host; 3) inducing the immunocytes to produce IFN-α to modulate virus infection.This is the first study demonstrating the excretion of RNA in gastrointestinal commensal bacteria. Extracellular RNA may function as a new signaling molecule in the cross-talk between host and commensal bacteria.