Molecular response of Pseudomonas aeruginosa to rosemary essential oil and chlorogenic acid at subinhibitory concentration revealed by comparative transcriptomic approach

Pseudomonas aeruginosa is a ubiquitous Gram(-) bacterium, classified as an ESKAPE pathogen with emerging multidrug resistance development and increasing prevalence among hospitals, aquacultures, and foods, which is mostly related to efficient adaptation strategies to conventional antimicrobials. Therefore, there is an urgent need to research P. aeruginosa's response to alternative antimicrobial compounds that are promising approaches in combating their survival and pathogenesis. The following study evaluated the transcriptomic response of P. aeruginosa NT06 food-isolate to subinhibitory concentration (subMIC) of rosemary essential oil combined with chlorogenic acid (REO-CGA). REO was obtained by hydrodistillation from dried leaves of Rosmarinus officinalis L. and characterized by GC-MS analysis, indicating 1,8-cineole as the major compound (52.6%). Micro broth dilution method was employed to establish the antimicrobial activity of REO, CGA, and their combination, and subMIC was used to study the growth kinetics during 72 h of incubation. RNA-seq was employed to establish the differentially expressed genes (DEGs), which were functionally annotated using GO terms and KEGG pathways. DEGs were mostly involved in the metabolism of aromatic compounds, energy acquisition, survival under oxygen limitation, spoilage, adaptation, and protection abilities. This study presents the implantation of molecular and bioinformatic approaches to deepen understanding of the REO-CGA mode of action and adaptive strategies of P. aeruginosa food isolate to those antimicrobials.