2,4-Di-Tert-Butylphenol Isolated From an Endophytic Fungus, Daldinia eschscholtzii, Reduces Virulence and Quorum Sensing in Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is among the top three gram-negative bacteria according to the WHO's critical priority list of pathogens against which newer antibiotics are urgently needed and considered a global threat due to multiple drug resistance. This situation demands unconventional antimicrobial strategies such as the inhibition of quorum sensing to alleviate the manifestation of classical resistance mechanisms. Here, we report that 2,4-di-tert-butylphenol (2,4-DBP), isolated from an endophytic fungus, Daldinia eschscholtzii, inhibits the quorum-sensing properties of P. aeruginosa. We have found that treating P. aeruginosa with 2,4-DBP substantially reduced the secretion of virulence factors as well as biofilm, and its associated factors that are controlled by quorum sensing, in a dose-dependent manner. Concomitantly, 2,4-DBP also significantly reduced the expression of quorum sensing-related genes, i.e., lasI, lasR, rhlI, and rhlR significantly. Importantly, 2,4-DBP restricted the adhesion and invasion of P. aeruginosa to the A549 lung alveolar carcinoma cells. In addition, bactericidal assay with 2,4-DBP exhibited synergism with ampicillin to kill P. aeruginosa. Furthermore, our computational studies predicted that 2,4-DBP could bind to the P. aeruginosa quorumsensing receptors LasR and RhlR. Collectively, these data suggest that 2,4-DBP can be exploited as a standalone drug or in combination with antibiotic(s) as an anti-virulence and anti-biofilm agent to combat the multidrug resistant P. aeruginosa infection.

Daldiniaeschsone A, a Rare Tricyclic Polyketide Having a Chromone Unit Fused to a δ-Lactone and Its Symmetrical Biphenyl Dimer, Daldiniaeschsone B, from an Endophytic Fungus Daldinia eschscholtzii SDBR-CMUNKC745

“…Due to the short period to scale up and the diversity production of secondary metabolites, fungi have become the new resource for natural products. The genus Daldinia belonging to the Xylariaceae is a genus of fungi that produces polyketide compounds with diverse structures and impressive biological activities, including immunosuppressive, cytotoxic, antiangiogenesis, anti-inflammatory, and antibacterial activities [ 1 , 2 , 5 , 6 , 7 , 8 ]. The two most investigated Daldinia species are D. eschscholtzii and D. concentrica which have produced many new compounds having remarkable biological activities including α -glucosidase inhibitory, antiangiogenesis, and anti-HIV activities [ 1 , 2 , 9 , 10 ].…”

The Impact of an Efflux Pump Inhibitor on the Activity of Free and Liposomal Antibiotics against Pseudomonas aeruginosa

“…Regulates elastase, protease, exotoxin A, biofilm formation and induces PQS and Rhl systems [34,35] Protease Immune invasion and host tissue damage [7,29] MexXY-OprM Aminoglycosides, fluoroquinolones, tetracyclines and macrolides [22][23][24] RhlI/R (C 4 -HSL)…”

“…Regulates the expression of pyoverdine, pyocyanin, rhamnolipids and the RhlI/R system [35] Pyoverdine Iron scavenging, vital for pathogenesis. Sequestrates iron from host, which is used for biofilm formation [40] MexEF-OprN Chloramphenicol, tetracycline, fluoroquinolones, HHQ 2 (QS signal) [39] Lipase Degrades lipids in the host [29] 1 Pseudomonas quinolone signal, 2 4-hydroxy-2-heptylquinoline.…”

“…N-butanoyl-homoserine lactone (C 4 -HSL) signals produced by the Rhl system freely diffuse out of the cells, while 3OC 12 -HSL and PQS signals produced by Las and PQS, respectively, need to be exported by membrane transporters to cross the outer membrane [ 21 , 25 ]. P. aeruginosa upregulates virulence factors such as pyocyanin, proteases, motilities and forms robust biofilms through QS, causing destructive infections and inflammations [ 28 , 29 , 30 ]. Pyocyanin is a redox-active toxin that plays a crucial role in the establishment of P. aeruginosa ’s infection, while proteases and lipases target and degrade the host’s proteins and lipids to facilitate the bacterium’s invasion [ 29 ].…”

“…P. aeruginosa upregulates virulence factors such as pyocyanin, proteases, motilities and forms robust biofilms through QS, causing destructive infections and inflammations [ 28 , 29 , 30 ]. Pyocyanin is a redox-active toxin that plays a crucial role in the establishment of P. aeruginosa ’s infection, while proteases and lipases target and degrade the host’s proteins and lipids to facilitate the bacterium’s invasion [ 29 ]. Pyoverdine, on the other hand, is a siderophore used for scavenging iron, vital for bacterial growth and virulence [ 31 ].…”