THE TOXIN-ANTITOXIN SYSTEM OF PLASMID pRC18 INCREASES THE SENSITIVITY OF THE LACTOBACILLUS CURVATUS STRAIN SAC7 TO LACTOCIN705

ARISTIMUÑO FICOSECO MARIA CECILIA; JULIANA BLECKWEDEL; GRACIELA VIGNOLO; RAÚL R. RAYA

San Miguel de Tucumán

Simposio; IV Simposio Internacional de Bacterias Lácticas (SIBAL) Alimentos, Salud y Aplicaciones.; 2013

Centro de Referencia para Lactobacilo CERELA

TypeII chromosomal toxin-antitoxin (TA) modules consist of a pair of genes thatencode two components: a stable toxin and a labile antitoxin. This toxin is co-expressed and neutralized withtheir cognate antitoxin from a TA (toxin-antitoxin) operon in normally growingcells. Under stress conditions, the antitoxin is readily degraded allowing thetoxin to exert their toxic effect causing the cell death. Thelactic acid bacterium Lactobacillus curvatus CRL 705 harbors plasmidpRC18, which is associated with the production of Lactocin Lac705, atwo-component bacteriocin. Recent sequencing studies describe the presence of aputative TA module (partitioning locus) on plasmid pRC18, which is organized ina single operon that produces a 92-amino-acids antitoxin (orf3) and a118-amino-acids toxin (orf2); these proteins belong, respectively, to the superfamiliesPhdYeFM and RelE.Cells derived from the strain CRL705, AR3and Sac7 (Lac-/Lacs), showed differentsensitivity to the action of thebacteriocin Lactocin 705 being more sensitive the strain Sac7 thanthe strain AR3. Thedifference between bothcells is that the strainSac7 still have the plasmid pRC18 while the strain AR3 is cured. The presence of the TA system of plasmid pRC18 could be associatedwith greater sensitivities ofSac7.To confirm, a new plasmid was constructed pRA1ta, a p3B1 derivative which containsthe pRC18-TA functions. The strain AR3 wastransformed with this plasmid (AR3::pRA1ta) and sensitivity assays were performed, this strain showed more sensitive than the wild type strain AR3. Theseresults suggest that the toxicfunction of the toxin could be induced by stress factors like the bacteriocin Lactocina 705.