P683
HYDROLYTIC ENZYMES AND BIOACTIVE SECONDARY METABOLITES IN
BURKHOLDERIA GLADIOLI PV. AGARICICOLA ARE QUORUM SENSING REGULATED AND APPEAR TO HAVE A ROLE IN THE PATHOGEN VIRULENCE ON
AGARICUS BISPORUS
Daniela Lamorte§1, Hazem S. Elshafie§1,2, Giulia Devescovi3, Pietro Lo Cantore1,
Sabino Bufo2, Vittorio Venturi3, Nicola Sante Iacobellis1
1Scuola di Scienze Agrarie, Forestali, Alimentari ed Ambientali
2Dipartimento di Scienze, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano,
85100, Potenza, Italy
3The International Centre for Genetic Engineering and Biotechnology, Area Science Park
Padriciano 99, 34149 Trieste, Italy
e-mail: nicola.iacobellis@unibas.it
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 possibly involved in the mushroom-pathogen interaction. In this study AHLdeficient mutants of four virulent strains of Bga were constructed by allelic exchange and
tested for various phenotypes including (i) antibacterial activity against Bacillus
megaterium and Escherichia coli, (ii) production of antimicrobial and haemolytic
substances, (iii) chitinase, protease and glucanase activities and (iv) virulence on
Agaricus bisporus pseudo-tissues blocks and whole basidiomes. AHLs-deficient mutants
showed a significant reduction in antibacterial activity and virulence on A. bisporus
pseudo-tissues blocks and whole basidiomes, the lack of the haemolytic, an also the
reduction of chitinolytic, proteolytic and glucanolytic activities. Culture extracts of the
mutants showed low antimicrobial activity against B. megaterium and E. coli and the lack
of haemolytic activities when compared to the parental strains. HPLC analysis of the
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 Quorum Sensing, mediated by AHLs, in the regulation of the above traits which are
mostly likely important in the pathogen virulence.