3&#x2010;Indolylacetonitrile Decreases <i>Escherichia coli</i> O157:H7 Biofilm Formation and <i>Pseudomonas aeruginosa</i> Virulence

다국어 초록 (Multilingual Abstract)

<P><B>Summary</B></P><P>Intercellular signal indole and its derivative hydroxyindoles inhibit <I>Escherichia coli</I> biofilm and diminish <I>Pseudomonas aeruginosa</I> virulence. However, indole and bacterial indole derivatives are unstable in the microbial community because they are quickly degraded by diverse bacterial oxygenases. Hence, this work sought to identify novel, non‐toxic, stable and potent indole derivatives from plant sources for inhibiting the biofilm formation of <I>E. coli</I> O157:H7 and <I>P. aeruginosa</I>. Here, plant auxin 3‐indolylacetonitrile (IAN) was found to inhibit the biofilm formation of both <I>E. coli</I> O157:H7 and <I>P. aeruginosa</I> without affecting its growth. IAN more effectively inhibited biofilms than indole for the two pathogenic bacteria. Additionally, IAN decreased the production of virulence factors including 2‐heptyl‐3‐hydroxy‐4(1<I>H</I>)‐quinolone (PQS), pyocyanin and pyoverdine in <I>P. aeruginosa</I>. DNA microarray analysis indicated that IAN repressed genes involved in curli formation and glycerol metabolism, whereas IAN induced indole‐related genes and prophage genes in <I>E. coli</I> O157:H7. It appeared that IAN inhibited the biofilm formation of <I>E. coli</I> by reducing curli formation and inducing indole production. Also, corroborating phenotypic results of <I>P. aeruginosa</I>, whole‐transcriptomic data showed that IAN repressed virulence‐related genes and motility‐related genes, while IAN induced several small molecule transport genes. Furthermore, unlike bacterial indole derivatives, plant‐originated IAN was stable in the presence of either <I>E. coli</I> or <I>P. aeruginosa</I>. Additionally, indole‐3‐carboxyaldehyde was another natural biofilm inhibitor for both <I>E. coli</I> and <I>P. aeruginosa</I>.</P>