DEGRADATION OF BACTERIAL QUORUM SENSING MOLECULES BY Rhodotorula sp.

NIETO PEÑALVER CG; LEGUINA AC; GIULIANO DEGRASSI; IRAZUSTA V; VITTORIO VENTURI; LUCÍA INÉS FIGUEROA DE CASTELLANOS

Congreso; IX SAMIGE Congreso Argentino de Microbiología general; 2013

Microorganisms can regulate their physiology in a cell concentration-dependent manner through theproduction of small regulatory molecules, the concentration of which is directly related to the density ofthe population. This phenomenon, known as quorum sensing (QS), has largely been described in bothGram positive and negative bacteria. Since it has been related to the control of the production ofvirulence and colonization factors, the QS regulatory system has also been studied as a putativecontrol mechanism for pathogenic microorganisms. Lactonases and acylases inactivate the QSsystems of Gram negative bacteria through the hydrolysis of N-acyl homoserine lactones (AHLs), themain signal molecules produced by this group of microorganisms. These enzymes have been isolatedfrom bacteria belonging to the genera of Bacillus, Pseudomonas, Streptomyces, Comomonas, andRalstonia, among others. In this work evidence presented shows that Rhodotorula sp., pigmentedyeast previously isolated from a filter plant of a copper mine in the province of Tucumán, Argentina,has the capacity of inactivating a wide range of AHLs. Rhodotorula sp. was cultured in YM medium inthe presence of 1μM of the following AHLs: C6-HSL, C8-HSL, C10-HSL, C12-HSL, 3-oxo-C6-HSL,3-oxo-C8-HSL, 3-oxo-C10-HSL and 3-oxo-C12-HSL. After incubation, the remaining AHLs in thesupernatants were analyzed with bioassays in plates developed with the biosensors Chromobacteriumviolaceum CV026, C. violaceum Vir07 and Agrobacterium tumefaciens NTL4 (pCF218) (pCF372).Results show that Rhodotorula sp. could completely inactivate AHLs with short (C6- and C8-HSLs)and long acyl chains (10- and C12-HSLs). In addition, this pigmented yeast presentedAHL-inactivating activity against substituted (3-oxo-derivative) and unsubstituted signal molecules. Incontrast to acylases, lactonases hydrolyze AHLs through the opening of the lactone ring that ispresent in all this type of molecules. The proteinaceous nature of the AHL-inactivating activity could beestablished after incubating a Rhodotorula sp. protein extract with pronase. To study the putativemechanism of signal inactivation by Rhodotorula sp., supernatants were acidified with HCl in order topermit the closure of the lactone ring, and analyzed as described before. The partial recovery of theregulatory activity in the samples suggests that the yeast hydrolyze AHLs through the production ofone or more lactonases. Taking together, these results show the potential of Rhodotorula sp. toproduce enzymes that interfere with quorum sensing systems of pathogenic bacteria.