Ethanolic Allium sativum extract down-regulates the pelF gene involved in Pseudomonas aeruginosa biofilm formation

Exploration of efficacious plant extracts that can reduce or inhibit Pseudomonas aeruginosa biofilm formation is necessary. Allium sativum is a suitable candidate because of its relative abundance. This study was carried out to determine the effect of ethanolic A. sativum extract on the expression of the P. aeruginosa biofilm gene, pelF. The presence of the pelF gene in the isolates used for this study was confirmed via polymerase chain reaction (PCR) and agarose gel electrophoresis. P. aeruginosa cultures treated with 1 g/ml of the A. sativum extract had the least turbidity (6.7 absorbance value at A600). The expression profile of the pelF gene in the treated cultures was determined via PCR using cDNA synthesized from RNA isolated from the treated P. aeruginosa cultures. The amplicons from the PCR were analyzed via agarose gel electrophoresis and a concentration dependent down-regulation of the pelF gene was observed. Further quantification of the pelF gene’s expression was performed via real-time PCR using rpoB as the reference gene. A 4-fold down-regulation of the gene was observed at 0.5 and 1 g/ml concentrations, respectively. This study suggests that the suppression of the pelF gene of P. aeruginosa by A. sativum extracts plays a role in the inhibition of P. aeruginosa biofilm formation. This is the first study to elucidate the effect of A. sativum on the expression of any of the pel genes. Key words: Allium sativum, biofilm, cDNA, down-regulation, gene expression, pelF, Pseudomonas aeruginosa, quantitative polymerase chain reaction (qPCR).