AUTHOR=Hassan Ramadan , Shaaban Mona I. , Abdel Bar Fatma M. , El-Mahdy Areej M. , Shokralla Shadi 

TITLE=Quorum Sensing Inhibiting Activity of Streptomyces coelicoflavus Isolated from Soil

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00659

DOI=10.3389/fmicb.2016.00659

ISSN=1664-302X

ABSTRACT=<p>Quorum sensing (QS) systems communicate bacterial population and stimulate microbial pathogenesis through signaling molecules. Inhibition of QS signals potentially suppresses microbial infections. Antimicrobial properties of <italic>Streptomyces</italic> have been extensively studied, however, less is known about quorum sensing inhibitory (QSI) activities of <italic>Streptomyces</italic>. This study explored the QSI potential of <italic>Streptomyces</italic> isolated from soil. Sixty-five bacterial isolates were purified from soil samples with morphological characteristics of <italic>Streptomyces</italic>. The three isolates: S6, S12, and S17, exhibited QSI effect by screening with the reporter, <italic>Chromobacterium violaceum</italic>. Isolate S17 was identified as <italic>Streptomyces coelicoflavus</italic> by sequencing of the hypervariable regions (V1–V6) of 16S rRNA and was assigned gene bank number KJ855087. The QSI effect of the cell-free supernatant of isolate S17 was not abolished by proteinase K indicating the non-enzymatic activity of QSI components of S17. Three major compounds were isolated and identified, using spectroscopic techniques (1D, 2D NMR, and Mass spectrometry), as behenic acid (docosanoic acid), borrelidin, and 1<italic>H</italic>-pyrrole-2-carboxylic acid. 1<italic>H</italic>-pyrrole-2-carboxylic acid inhibited QS and related virulence factors of <italic>Pseudomonas aeruginosa</italic> PAO1 including; elastase, protease, and pyocyanin without affecting <italic>Pseudomonas</italic> viability. At the molecular level, 1<italic>H</italic>-pyrrole-2-carboxylic acid suppressed the expression of QS genes (<italic>lasI, lasR, lasA, lasB, rhlI, rhlR, pqsA</italic>, and <italic>pqsR</italic>). Moreover, QSI activity of S17 was assessed under different growth conditions and ISP2 medium supplemented with glucose 0.4% w/v and adjusted at pH 7, showed the highest QSI action. In conclusion, 1<italic>H</italic>-pyrrole-2-carboxylic acid, one of the major metabolites of <italic>Streptomyces</italic> isolate S17, inhibited QS and virulence determinants of <italic>P. aeruginosa</italic> PAO1. The findings of the study open the scope to exploit the <italic>in vivo</italic> efficacy of this active molecule as anti-pathogenic and anti-virulence of <italic>P. aeruginosa</italic>.</p>