Transcriptome analysis reveals the resistance mechanism of Pseudomonas aeruginosa to tachyplesin I

Abstract

Background: Tachyplesin I is a cationic antimicrobial peptide with a typical cyclic anti-parallel β-sheet structure. We previously demonstrated that long-term continuous exposure to increased concentration of tachyplesin I can induce resistant Gram-negative bacteria. However, no significant information is available about the resistance mechanism of Pseudomonas aeruginosa (P. aeruginosa) to tachyplesin I. Materials and Methods: In this study, the global gene expression profiling of P. aeruginosa strain PA-99 and P. aeruginosa CGMCC1.2620 (PA1.2620) was conducted using transcriptome sequencing. For this purpose, outer membrane permeability and outer membrane proteins (OMPs) were further analyzed. Results: Transcriptome sequencing detected 672 upregulated and 787 downregulated genes, covering Clusters of Orthologous Groups (COGs) of P. aeruginosa strain PA-99 compared with PA1.2620. Totally, 749 differentially expressed genes (DEGs) were assigned to 98 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and among them, a two-component regulatory system, a beta-lactam resistance system, etc. were involved in some known genes resistant to drugs. Additionally, we further attempted to indicate whether the resistance mechanism of P. aeruginosa to tachyplesin I was associated with the changes of outer membrane permeability and OMPs. Conclusion: Our results indicated that P. aeruginosa resistant to tachyplesin I was mainly related to reduced entry of tachyplesin I into the bacterial cell due to overexpression of efflux pump, in addition to a decrease of outer membrane permeability. Our findings were also validated by pathway enrichment analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR). This study may provide a promising guidance for understanding the resistance mechanism of P. aeruginosa to tachyplesin I.