INHIBITION OF EARLY STAGES OF SALMONELLA TYPHIMURIUM BIOFILMS BY EXTRACELLULAR DNA (EDNA) AND GENOMIC DNA (GDNA)

Abstract

In this study, the role of extracellular DNA in the establishment and maintenance of Salmonella biofilms was investigated. As a result of spectrophotometric measurements using PicoGreen® dye, it was determined that planktonic cells contain less eDNA compared to their biofilm counterparts. As a result of incubation at  20 °C for 24h, eDNA contents of planktonic Salmonella Typhimurium SL1344 and DMC4 cells were determined as 206 ng/ml and 211 ng/ml, respectively. However, eDNA amounts increases to 313.18 ng/ml for SL1344 and 319.37 ng/ml for DMC4 at biofilm structure of the same strains. The effects of extracellular DNA (eDNA) released from biofilm cells and genomic DNA (gDNA) isolated from Salmonella cells on the biofilm formation in the bacteria were investigated using DNase I and Benzonase enzymes that digest DNA. In the experiments where both enzymes were applied, the active fragmentation of eDNA and gDNA resulted in a statistically significant (p <0,01) decrease in biofilm formation at the end of 24 hours compared to non-enzyme treated samples, but this effect disappeared after 48 hours of incubation.