Bacterial extracellular vesicles: biotechnological perspective for enhanced productivity

Abstract

Bacterial extracellular vesicles (BEVs) are non-replicative nanostructures released by Gram-negative and Gram-positive bacteria as a survival mechanism and inter- and intraspecific communication mechanism. Due to BEVs physical, biochemical, and biofunctional characteristics, there is interest in producing and using them in developing new therapeutics, vaccines, or delivery systems. However, BEV release is typically low, limiting their application. Here, we provide a biotechnological perspective to enhance BEV production, highlighting current strategies. The strategies include the production of hypervesiculating strains through gene modification, bacteria culture under stress conditions, and artificial vesicles production. We discussed the effect of these production strategies on BEVs types, morphology, composition, and activity. Furthermore, we summarized general aspects of BEV biogenesis, functional capabilities, and applications, framing their current importance and the need to produce them in abundance. This review will expand the knowledge about the range of strategies associated with BEV bioprocesses to increase their productivity and extend their application possibilities.

Keywords: Artificial bacterial vesicles; Bacterial extracellular vesicles (BEVs); Hypervesiculation strains; Vesiculation cellular response to stress.

Fig. 1

Biogenesis mechanisms of Bacterial Extracellular Vesicles (BEVs) models: (A) Blebbing and B) explosive cell lysis in Gram-negative bacteria, (C) Budding of the cellular membrane (CM) and (D) bubbling cell death in Gram-positive bacteria, and (E) nanotube formation in both. Blebbing and budding can be caused by factors such as loss of cross-links between peptidoglycan (PG) and outer membrane (OM), changes in the membrane composition, molecules intercalation like with Pseudomonas Quinolone Signals (PQS), or turgor pressure due to molecule accumulation in the cell wall, i.e., LPS and PG fragments, proteins, or Phenol-soluble modulins (PSMs). The explosive cell lysis and bubbling cell death are attributed to endolysins. Endolysins degrade the PG, damaging cells. Nanotubes are generated by the extrusion of the cellular membrane (CM) in Gram-positive bacteria and OM in Gram-negative bacteria. Created with Servier Medical Art resources

Fig. 2

Biological functions of Bacterial Extracellular Vesicles (BEVs): bacterial survival, bacterium-bacterium communication, and bacterium-host communication. BEVs may act like decoys and release key enzymes involved in activities such as substrate degradation, metal acquisition, or antibiotic resistance. BEVs also help the cell release pressure. BEVs play beneficial or antagonistic roles during the communication process with other cells. They can transfer genes, enzymes, molecules to activate quorum sensing, and substrates to other bacteria. Also, BEVs could carry virulence factors to promote invasion by pathogenic bacteria

Fig. 3

Bacterial Extracellular Vesicles (BEVs) applications. BEVs are biotherapeutics in the treatment of cancer, depression, or organ inflammation. BEVs as molecule transport systems. BEVs in the production of vaccines and antimicrobial compounds. BEVs as biomarkers, like tuberculosis screening. BEVs as a biotechnology tool for the study of lipid membrane permeability and membrane proteins. BEVs as nanoreactors in bioremediation or substrates enzymatic transformation. Created with Biorender.com

Fig. 4

Strategies to increase the productivity of BEVs and updated bibliometric data on these strategies. (A) Bibliometrics data associated with abundant BEV production strategies over the last fifty years. (B) Publications report related to the genetic modifications of relevant proteins related to abundant vesiculation. (C) Publications report related to environmental and chemical stress conditions that lead to the abundant release of BEVs during bacteria culture. (D) Publications report related to methodologies employed by the artificial BEVs production