Chromobacterium violaceum delivers violacein, a hydrophobic antibiotic, to other microbes in membrane vesicles

Abstract

This study describes Chromobacterium violaceum's use of extracellular membrane vesicles (MVs) to both solubilize and transport violacein to other microorganisms. Violacein is a hydrophobic bisindole with known antibiotic activities against other microorganisms. Characterization of the MVs found they carried more violacein than protein (1.37 AE 0.19-fold), suggesting they may act as a reservoir for this compound. However, MVs are not produced in response to violaceina ΔvioA isogenic mutant, which is incapable of making violacein, actually produced significantly more MVs (3.2-fold) than the wild-type strain. Although violacein is insoluble in water (Log P octanol: water = 3.34), 79.5% remained in the aqueous phase when it was present within the C. violaceum MVs, an increase in solubility of 1740-fold. Moreover, tests with a strain of Staphylococcus aureus showed MVassociated violacein is bactericidal, with 3.

Integral Characterization of the 16S rRNA Gene of Non-sporulating Bacteria and Its Action Against Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae)

“…Infection of this bacterium in humans occurs through exposure of open wounds in contact with the waters of streams, rivers and lakes, and also in contaminated soil (Thwe, Ortiz, & Wankewicz, 2020). Studies on violacein, a violet-colored substance, have shown effective effects against several bacteria, especially gram-positive ones, even combating multidrug-resistant strains of Staphylococcus aureus (Choi, Lim, Cho, & Mitchell, 2020). Violacein is detected in several environments and its role should be widespread regarding habitats and microorganisms (Choi, Yoon, Lee, & Mitchell, 2015).…”

Assessment of in vitro cytotoxicity of imidazole ionic liquids and inclusion in targeted drug carriers containing violacein

“…Viol is released from bacteria via membrane vesicles. 1 Several potential clinical uses of Viol are described in the literature such as microbiocide activity targeting the cytoplasmic membrane of Gram-positive microorganisms, 2,3 antiplasmodial and trypanocidal, 4 analgesic, 5 antitumoral and virucide among others recently reviewed. 6 Additionally, Viol was reported as an immunostimulatory molecule that is mediated by TLR8 and relevant for immunosuppressed patients.…”

Death in a sphere: Chromobacterium violaceum secretes outer membrane vesicles filled with antibiotics

“…When incubating S. aureus with purified violacein, OMVs from C. violaceum or from mutants unable to produce violacein, they found that S. aureus was killed by purified violacein or violacein solubilized by OMVs. Based on these results, the researchers hypothesised that C. violaceum produces violacein, which is packed into OMVs, and secretes the OMVs into the environment where they eventually encounter S. aureus cells leading to their growth inhibition (Choi et al ., ).…”

“…These OMVs represent the only available shuttle for C. violaceum to secrete a toxic hydrophobic compound into the environment, where its role would be that of inhibiting the growth of competitors. However, C. violacein still secretes OMVs although it is not producing violacein indicating that violacein production is not a trigger for OMV secretion (Choi et al ., ). This raises the question of what the general function of OMVs in this bacterium might be.…”

“…A study by Choi et al . () demonstrated that violacein is incorporated within OMVs that increase its solubility. Notably, the researchers found that in a coculture of S. aureus and C. violaceum , growth of the S. aureus population was inhibited by C. violaceum and that this inhibition started at the same time point at which C. violaceum starts producing violacein.…”