Studying factors involved in biogenesis of Lysobacter sp. XL1 outer membrane vesicles

Abstract

The Gram-negative bacterium Lysobacter sp. XL1 produces outer membrane vesicles that are heterogeneous in size, density, and protein composition. One of the subpopulations is secretory vesicles for lytic protease L5 of Lysobacter sp. XL1 (Kudryakova et al. (2015) FEMS Microbiol. Lett., 362, fnv137). Protein L5 was assumed to influence biogenesis of these secretory vesicles that contain it. Using a Pseudomonas fluorescens Q2-87/B expression system, it was shown that the recombinant L5 protein may act as a factor of vesicle biogenesis. This points to a possible involvement of L5 protein in Lysobacter sp. XL1 vesicle biogenesis. Furthermore, it was established that the main phospholipid of Lysobacter sp. XL1 vesicles is cardiolipin, and vesicles are formed predominantly of outer membrane regions enriched with this phospholipid. This indicates that cardiolipin participates in biogenesis of all vesicle subpopulations in Lysobacter sp. XL1.

Deletion of alpB Gene Influences Outer Membrane Vesicles Biogenesis of Lysobacter sp. XL1

“…It was found that in the recombinant strain, protein L5 was contained in vesicles. Cells of the recombinant strain were shown to form a larger number of vesicles as compared with the parent strain (Kudryakova et al, 2017). All these data indirectly confirmed the involvement of bacteriolytic protein L5 in the biogenesis of that group of vesicles by means of which it was released into the extracellular milieu.…”

“…Further investigation of the biogenesis revealed that the main phospholipid of Lysobacter sp. XL1 vesicles was cardiolipin (Kudryakova et al, 2017). That meant that vesicles formed from OM loci enriched with this phospholipid.…”

“…XL1 forms several subpopulations of vesicles from OM loci enriched with CL. The hydrophilic head of cardiolipin carries two negative charges, and, due to their intermolecular repulsion, the rigidity of the OM can be disturbed in loci enriched with this phospholipid, which leads to the initiation of vesicle formation (Kudryakova et al, 2017). One of the vesicle subpopulations contains bacteriolytic enzyme L5.…”

“…Research into the OMV biogenesis of Lysobacter sp. XL1 found their formation to occur in OM segments enriched with cardiolipin (Kudryakova et al, 2017). Fractionation of vesicles revealed a group/subpopulation of vesicles containing protein L5.…”

TTAPE-Me dye is not selective to cardiolipin and responds to main anionic phospholipids unspecifically

“…The functions of CL are diverse. Besides crucial role in bioenergetics, including mitochondrial membrane morphology [2], CL is associated with many cellular and protein abnormalities and human diseases [3,4]; involved in stabilization and activation of proteins in energy transducing membranes [5][6][7][8]; produces polar lipid microdomains [1,9,10]; serves as a targets for antimicrobials [11,12]; controls distribution of bacterial cell division proteins [13]; sequester antibiotics apart of the division septum in bacteria [11,12]; changes ordering and rigidity of the lipid bilayer [14]; contributes to bacterial adaptation to environmental stress [15,16]; connects size and growth rate of bacterial cells [17] probably via its asymmetric distribution [18]; drives generation of outer membrane-derived vesicles by pathogenic bacteria [19]; serves as a signal for mitophagy [20,21]; triggers production of antiphospholipid antibodies in pre-apoptotic cells due to its exposure to the cell surface [22,23].…”