Role of Outer Membrane Vesicles in Serratia grimesii Interactions with Caco-2 Cells

Non-pathogenic bacteria Serratia grimesii able to enter eukaryotic cells, but the mechanisms of their invasive activity are still unknown. We have previously shown that S. grimesii could in vitro secrete outer membrane vesicles (OMVs) that itself penetrate eukaryotic cells and enhance the invasion of S. grimesii into these cells (Bozhokina et al., 2020). Therefore, the aim of this work is to study the role of S. grimesii OMVs in the process of interaction between bacteria and the host cell. Our results obtained that exposure to cold shock or oxidative stress caused by hydrogen peroxide increases the secretion of OMVs by S. grimesii , and isolated vesicles enhance bacterial invasion into CaCo-2 cells. In addition, S. grimesii OMVs induce immune response of CaCo-2 cells, and reveal cytotoxic activity towards these cells, determined by the level of release of lactate dehydrogenase from cell cytoplasm. In the presence of outer membrane vesicles obtained under stress conditions, bacteria could more actively adhere and penetrate into CaCo-2 cells. In addition, a participation of cell surface receptor E-cadherin in S. grimesii OMVs invasion into CaCo-2 cells was demonstrated for the first time. The obtained results suggest that OMVs-mediated delivery of virulence factors to eukaryotic cells may significantly contribute to the pathogenesis caused by S. grimesii infection.