Influence of nonpolar aliphatic amino acids on Pseudomonas aeruginosa for virulence factors production

Multidrug-resistant (MDR) microorganisms are widely recognized as a public health concern due to the antibiotic resistance, which is a major risk to global human health. Amino acids have been utilized to produce antimicrobial peptides as they are extremely effective and less likely to build microbial resistance. This study evaluates the efficacy of six aliphatic amino acids, isoleucine, methionine, valine, glycine, alanine, and proline against Pseudomonas aeruginosa. It is a Gram-negative MDR pathogen that utilizes N-acyl-homoserine lactones as signaling molecules to regulate the quorum sensing pathway and express virulence factors. The MIC and sub-MIC were determined by the broth dilution method. This finding reveals that isoleucine exhibits a higher inhibitory effect on the organism at MIC and sub-MIC concentration of amino acids compared to the inhibition by other amino acids. The biofilm production was inhibited at a higher percentage, and also EPS production was inhibited in treatment with isoleucine. Confocal laser scanning microscope results depicts the disintegration of biofilm formation upon treatment. The isoleucine-treated culture of P. aeruginosa effectively inhibits the toxic pyocyanin production. Pyoverdines play a crucial role in iron acquisition, and their production was found to be inhibited by isoleucine. Motility was observed by swimming and swarming, and the results obtained from the gene expression studies demonstrated that isoleucine, methionine, valine, and glycine inhibited more virulence gene expression compared to alanine and proline.