Indole and 7‐hydroxyindole diminish Pseudomonas aeruginosa virulence

Abstract

SummaryIndole is an extracellular biofilm signal for Escherichia coli, and many bacterial oxygenases readily convert indole to various oxidized compounds including 7‐hydroxyindole (7HI). Here we investigate the impact of indole and 7HI on Pseudomonas aeruginosa PAO1 virulence and quorum sensing (QS)‐regulated phenotypes; this strain does not synthesize these compounds but degrades them rapidly. Indole and 7HI both altered extensively gene expression in a manner opposite that of acylhomoserine lactones; the most repressed genes encode the mexGHI‐opmD multidrug efflux pump and genes involved in the synthesis of QS‐regulated virulence factors including pyocyanin (phz operon), 2‐heptyl‐3‐hydroxy‐4(1H)‐quinolone (PQS) signal (pqs operon), pyochelin (pch operon) and pyoverdine (pvd operon). Corroborating these microarray results, indole and 7HI decreased production of pyocyanin, rhamnolipid, PQS and pyoverdine and enhanced antibiotic resistance. In addition, indole affected the utilization of carbon, nitrogen and phosphorus, and 7HI abolished swarming motility. Furthermore, 7HI reduced pulmonary colonization of P. aeruginosa in guinea pigs and increased clearance in lungs. Hence, indole‐related compounds have potential as a novel antivirulence approach for the recalcitrant pathogen P. aeruginosa.

Efficacy of 7‐benzyloxyindole and other halogenated indoles to inhibit Candida albicans biofilm and hyphal formation

“…The previous studies have reported that indole inhibits biofilm formation and suppresses the virulence of bacterial strains such as Staphylococcus aureus , Agrobacterium tumefaciens (Lee and Lee, 2010; Lee et al ., 2013, 2015a,b; Lee et al ., 2016) and Vibrio cholera (Mueller et al ., 2009). Likewise, indole derivatives such as 7‐fluoroindole, 7‐hydroxyindole, 3‐indolyl acetonitrile and 2‐aminobenzimidazoles have been reported to exhibit antimicrobial activities against pathogenic bacteria (Lee et al ., 2009, 2011, 2012, 2015a,b; Frei et al ., 2012). …”

Isolation of Indole Utilizing Bacteria Arthrobacter sp. and Alcaligenes sp. From Livestock Waste

“…strain [25] use indole as a growth substrate. While, Pseudomonas indoloxidans, P. aeruginosa [7], A. tumefaciens [10], and Burkholderia unamae strain CK43-B [26] can degrade indole without utilizing it as the sole carbon source. D. indolicum is the only anaerobic isolate identified to date that can utilize indole as a carbon and electron donor [27].…”

“…There are more than 85 Gram-positive and Gram-negative bacterial species that yield indole as the product of tryptophan metabolism [1]. Biochemical and molecular studies have shown that indole plays various roles in bacterial systems, for example, as an extracellular signal [1,3], for multicopy plasmid maintenance [4], cell division, biofilm formation [5], and acid and drug resistance [5][6][7][8]. In addition, indole also controls the virulence of several pathogenic bacteria [7] and it has multifaceted properties and applications in prokaryotic systems [9][10][11] as well as eukaryotic systems [12].…”

Biotechnology of siderophores in high-impact scientific fields

“…An example of this statement is the production of the siderophore pyoverdine by Pseudomonas fluorescens (39), which is related to virulence and pathogenicity of the microbe at the clinical level (45)(46)(47). Nagata and co-workers (39) found that pyoverdine production enhanced iron nutrition of tomato plants (Strategy I plants, which cannot produce pyoverdine).…”