Table 1 Comparison between gram-negative and gram-positive extracellular vesicles

Origin

Outer membrane

Cytoplasmic membrane

[39]

Size

10 nm-300 nm

20 nm-400 nm

[39]

Components

Outer membrane proteins, periplasmic proteins, virulence factors, cytoplasmic proteins, inner membrane proteins, lipopolysaccharides, phospholipids, and peptidoglycan (10%-20%)

Cytoplasmic proteins, membrane-associated proteins, lipoteichoic acid (LTA), peptidoglycan (> 50%)

[39]

Genetic components

sRNA, mRNA, miRNA, luminal and surface associated DNA

sRNA, extracellular and chromosomal DNA

[39, 201]

Proteins

Outer membrane: OmpA, OmpC, OmpF, lipoprotein (Lpp), periplasmic: Alkaline phosphatase and AcrA

Single lipid membrane proteins: penicillin-binding, immunoglobulin G-binding (protein A), staphopain A, α-haemolysins, heat-shock protein

[42, 202]

Lipids

Glycerophopholipids, phosphatidylethanolamine, phophotidylglycerol and cardiolipin

Phosphatidylglycerol, myristic and palmitic acids

[120, 202]

Coagulation

E-selectin, P-selectin, thrombomodulin

Fibronectin binding protein, staphylocoagulase precursor, Vonwillebrand factor binding protein

[202]

Antibiotic resistance

β-lactamase, enzyme L5, multidrug efflux protein (Mtr, Mex, TolC)

β-lactamase, Penicillin-binding proteins: PBP1, PBP2, PBP2a, PBP3 and PBP4

[202]

Virulence factor delivery

Enzymes: phospholipase C, esterase lipase, alkaline phosphatase, serine protease Toxins: adenylatecyclase, cholera, cytolethal distending, PagJ, PagK1, VacA

InIB, LLO, IgG binding protein SbI, protective antigen, lethal factor, edema toxin, anthrolysin

[202]

Bacterial survival

Hemin-binding protein, TonB-dependent receptors

β-lactamase protein

[202, 203]

Bacteria adhesion and invasion

Adhesin/invasin, OmpA

Plasma binding proteins, staphopain A

[202]

Immune evasion

Cytotoxic necrotizing factor 1, UspA1/A2

Coagulation factors, antibody degradation and sequestering factors, complement inhibition factors

[46, 202]

Host-cell modulation

Cytolysin A, VacA toxin, CNF1, heat-liable enterotoxin, shigatoxin, Cif, flagellin, α-haemolysin

Proteolysin, β2 toxin

[202]

Killing competing bacteria

Endopeptidase L5, murein hydrolase (Mtl, Slt), peptidoglycan hydrolase

N-aetylmuramoyl-L-alanine amindase

[202]

Biogenesis

a. Loss or relocation of covalent linkages between the OM and the underlying peptidoglycan layer

b. Accumulation of peptidoglycan fragments in the outer leaflet of the OM

c. Misfolded proteins in periplasmic space exerting turgor pressure on OM

d. Enrichment of species-specific membrane curvature-inducing molecules

Action of cell wall-degrading enzymes; endolysin, autolysin

[36]

Lipids

Glycerophopholipids, phosphatidylethanolamine, phophotidylglycerol and cardiolipin

Phosphatidylglycerol, myristic and palmitic acids

[120, 202]

Coagulation

E-selectin, P-selectin, thrombomodulin

Fibronectin binding protein, staphylocoagulase precursor, Vonwillebrand factor binding protein

[202]