Antibiotics Stimulate Formation of Vesicles in Staphylococcus aureus in both Phage-Dependent and -Independent Fashions and via Different Routes

Abstract

Bacterial membrane vesicle research has so far focused mainly on Gram-negative bacteria. Only recently have Gram-positive bacteria been demonstrated to produce and release extracellular membrane vesicles (MVs) that contribute to bacterial virulence. Although treatment of bacteria with antibiotics is a well-established trigger of bacterial MV formation, the underlying mechanisms are poorly understood. In this study, we show that antibiotics can induce MVs through different routes in the important human pathogen Staphylococcus aureus. DNA-damaging agents and antibiotics inducing the SOS response triggered vesicle formation in lysogenic strains of S. aureus but not in their phage-devoid counterparts. The β-lactam antibiotics flucloxacillin and ceftaroline increased vesicle formation in a prophage-independent manner by weakening the peptidoglycan layer. We present evidence that the amount of DNA associated with MVs formed by phage lysis is greater than that for MVs formed by β-lactam antibiotic-induced blebbing. The purified MVs derived from S. aureus protected the bacteria from challenge with daptomycin, a membrane-targeting antibiotic, both in vitro and ex vivo in whole blood. In addition, the MVs protected S. aureus from killing in whole blood, indicating that antibiotic-induced MVs function as a decoy and thereby contribute to the survival of the bacterium.

Antimicrobial and Antivirulence Action of Eugenia brejoensis Essential Oil in vitro and in vivo Invertebrate Models

“…The activation of SOS response occurs when bacteria need to repair damages induced in the DNA due antibiotic treatment and other adverse conditions (Simmons et al, 2008;Silva et al, 2017). The activation of SOS pathway is associated with emergence of drug resistance and acquisition of virulence factors (Andreoni et al, 2019;Meunier et al, 2019). Our data also report that EbEO interferes with the regulation of the accessory gene regulator (agr)-mediated quorum sensing.…”

Cracking Open Bacterial Membrane Vesicles

“…In contrast to the explosive cell lysis induced by the action of endolysin in P. aeruginosa cells (Turnbull et al, 2016), the cytoplasmic membrane of B. subtilis cells protrudes through the holes in the peptidoglycan that are formed by the endolysin while the cell morphology remain intact (Toyofuku et al, 2017a(Toyofuku et al, , 2019 (Figure 1). Endolysintriggered MV formation has also been demonstrated in another Gram-positive bacterium, Staphylococcus aureus (Andreoni et al, 2019). Another peptidoglycan-hydrolyzing enzyme, autolysin, has been suggested to induce MV formation in S. aureus further indicating that cell wall damage is a key step in MV formation in Gram-positive bacteria (Wang et al, 2018).…”

Answers to naysayers regarding microbial extracellular vesicles

“…Curiously, EV release is increased in conditions of cellular stress, such as exposure to bacteriophages or antibiotics, which perturb cell wall or membranes [37]. In S. aureus, EVs formed by phage lysis or antibiotic treatment have different compositions [38]. While it is not clear if this is increased waste to cleanse damaged cellular components or a special case of EVs formed by autolysis (reviewed in [9]), EVs formed in conditions of stress are distinct from EVs from unperturbed cells.…”