Expression of quorum sensing genes
We performed gene assays to evaluate the impact of chitosan on the expression of QS-regulated lasR and rhlR genes. The P. aeruginosaisolate was cultivated in LB medium with or without chitosan at a concentration of 100 μg /ml. RNA was isolated using TRIzol reagent (Sigma-Aldrich, UK) and dissolved in 20 μl of 0.1% diethylpyrocarbonate (DEPC)-treated water. On the same day, cDNA was amplified using cDNA Synthesis kit (Yekta Tajhiz Azma Co, Iran) according to the manufacturer’s instructions. The quantitative polymerase chain reaction (qPCR) reactions were conducted using the 7500 Sequence Detection System (Applied Biosystems Inc., Foster, CA, USA) and Power SYBR Green PCR Master Mix (Applied Biosystems). Gene-specific primers were adopted from (Muslim et al., 2018a) listed in Table 3 were employed to determine the expression level of QS-regulated genes. The rpsL gene was utilized as a control to normalize the expression of lasR and rhlR genes, and the experiments were carried out in triplicate for real-time analysis.