AHLS MEDIATED QUORUM SENSING REGULATE HYDROLYTIC ENZYMES AND BIOACTIVE SECONDARY METABOLITES PRODUCTION, AND VIRULENCE IN BURKHOLDERIA GLADIOLI PV. AGARICICOLA Nicola Sante Iacobellis1, Daniela Lamorte§1 , Hazem S. Elshafie§1,2, Giuglia De Vescovi3, Pietro Lo Cantore1, Sabino Bufo2, Vittorio Venturi3 1Scuola di Scienze Agrarie, Forestali, Alimentari ed Ambientali, 2Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 85100, Potenza, Italy; The International Centre for Genetic Engineering and Biotechnology, Area Science Park Padriciano 99, 34149 Trieste, ITALY3. e-mail: firstname.lastname@example.org Recent studies showed that strains of Burkholderia gladioli pv. agaricicola (Bga), the causal agent of the soft rot of several cultivated mushroom species, produce an array of N-Acyl homoserine lactones (AHLs) which may be expected to regulate some biological activities of the producer and traits involved in the mushrooms-pathogen interaction. In this study AHLs-deficient mutants of four virulent strains of Bga were constructed by allelic exchange and their antagonistic activity against Bacillus megaterium and Escherichia coli, the production of antimicrobial and haemolytic substances, their chitinase, protease and glucanase activities as well as their virulence on Agaricus bisporus pseudo-tissues blocks and whole basidiomes were comparatively evaluated with the parental wild strains. AHLs-deficient mutants showed a highly reduction in antagonistic activity and virulence on Agaricus bisporus pseudo-tissues blocks and whole basidiomes, the lack of the haemolytic activity as well as reduced chitinolytic, proteolytic and glucanolytic activities . Culture extracts of the mutants showed a low antimicrobial activities against B. megaterium and E. coli and the lack of haemolytic activities when compared to the parental strains. HPLC analysis of the above culture extracts confirmed the absence/lower level of the typical bioactive substances present in the parental strains chromatograms. These results suggest the important role of QS, mediated by AHLs, in the regulation of the above traits which appear important in the pathogen virulence.
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