Abstract
Dynamic Light Scattering (DLS), Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM) are physical techniques widely employed to characterize the morphology and the structure of vesicles such as liposomes or human extracellular vesicles (exosomes). Bacterial extracellular vesicles are similar in size to human exosomes, although their function and membrane properties have not been elucidated in such detail as in the case of exosomes. Here, we applied the above cited techniques, in synergy with the thermotropic characterization of the vesicles lipid membrane using a turbidimetric technique to the study of vesicles produced by Gram-negative bacteria (Outer Membrane Vesicles, OMVs) grown at different temperatures. This study demonstrated that our combined approach is useful to discriminate vesicles of different origin or coming from bacteria cultured under different experimental conditions. We envisage that in a near future the techniques employed in our work will be further implemented to discriminate complex mixtures of bacterial vesicles, thus showing great promises for biomedical or diagnostic applications.
Highlights
In all domains of life Eukarya, Archaea, and Bacteria produce and release membrane vesicles for reasons that are still not completely understood (Deatherage and Cookson, 2012)
Following the procedure reported in this work, we were able to reach a concentration of ∼0.5 mg/ml of proteins for Outer-membrane vesicles (OMVs) samples obtained after culturing bacteria at 37◦C, ∼0.2 mg/ml for OMVs obtained at 27◦C, and ∼0.1 mg/ml for OMVs obtained at 20◦C
The thermotropic behavior of OMVs and bacteria grown at different temperatures have been studied
Summary
In all domains of life Eukarya, Archaea, and Bacteria produce and release membrane vesicles for reasons that are still not completely understood (Deatherage and Cookson, 2012). Many cells such as dendritic cells, lymphocytes, and tumor cells actively release (i.e. by exocytosis) small (∼30–100 nm of diameter) membrane vesicles, referred as exosomes, into biofluids. Membrane Phase Transition of OMVs (i.e. plasma/serum, urine, cerebrospinal fluid, and saliva). These vesicles are powerful cell-to-cell messengers as they transfer lipids, proteins, DNA, and ribonucleic acids (i.e. mRNA, microRNA, lncRNA, and other RNA species) between cells (Valadi et al, 2007; Simpson et al, 2009; Chen et al, 2012). The production and release of vesicles by bacteria is a natural process and it is necessary for interspecies (bacteria-bacteria) and inter-kingdom (bacteria-host) interactions (Leitão and Enguita, 2016)
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