The bacterial signalling molecule indole attenuates the virulence of the fungal pathogen Candida albicans.
OBJECTIVE
Indole is a signalling molecule, produced by a number of Gram-positive and Gram-negative bacteria both in nature as well as clinical environments. Here, we explored the effect of bacterial indole and one of its main derivatives on the virulence of the fungal pathogen Candida albicans.


RESULTS
We found that indole and its derivate indole-3-acetonitrile (IAN) did not affect the viability of C. albicans. Interestingly, indole and IAN repressed C. albicans biofilm formation as well as the attachment of C. albicans to intestinal epithelial HT-29 cells and inhibited the ability of the yeast to make filaments that are the main virulence factor of C. albicans. In addition, we used the heterologous model host Caenorhabditis elegans to demonstrate in vivo that the presence of indole or IAN attenuates C. albicans infection (P = 0.0188 and P < 0.0001 for indole and IAN, respectively, compared to worms exposed to C. albicans DAY185 alone) and decreases fungal colonization in the nematode gut. Importantly, quantitative real-time polymerase chain reaction (qRT-PCR) results showed that in C. albicans, indole and IAN strongly stimulated the transcription of NRG1.


CONCLUSIONS
Indole and IAN attenuates fungal virulence by regulating the transcription of NRG1, a transcriptional factor that influences filamentation and biofilm formation in C. albicans.


CONCLUSIONS
Our findings indicate that the bacterial signalling molecules indole and its derivatives play an inter-kingdom role in dynamic network of microbiota and directly modulate the virulence of fungal C. albicans via NRG1.
Department of Gastroenterology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
S
S
Oh
G W
GW
Go
E
E
Mylonakis
Y
Y
Kim
D000818:Animals; D018441:Biofilms / Q000187:drug effects; D017173:Caenorhabditis elegans / Q000382:microbiology; D002176:Candida albicans / Q000187:drug effects* / Q000472:pathogenicity*; D019073:HT29 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism
D007211:Indoles; D014157:Transcription Factors; D037521:Virulence Factors; C030374:indole; C016516:indole-3-acetonitrile