Transcriptome Analysis Reveals AI-2 Relevant Genes of Multi-Drug Resistant in Response to Eugenol at Sub-MIC.

Eugenol, the major active essential oil component of clove, was reported to possess QS (quorum sensing) inhibitory activity. A previous study found that eugenol could bind to quorum sensing receptors of and down-regulate the expression of virulence genes at sub-MIC (minimum inhibitory concentration) without affecting the bacterial growth. However, the alterations of QS signal molecules at transcription levels was not well understood. To better understand interactions of in response to eugenol and explore molecular regulations, transcriptome sequencing was performed. A total of 5779 differentially expressed genes (DEGs) enriched in a variety of biological processes and pathways were identified. The transcriptional data was validated by qPCR and the results showed that the expression profiles of 4 major genes involved in autoinducers-2 (AI-2) synthesis, including , , and were consistent with transcriptome analysis except for , a transcriptional repressor gene of lsr operon, which may repress the expression of following genes responsible for AI-2 signal transmission . AI-2 synthesis assay also revealed that eugenol could inhibit AI-2 generation. The results of our study offer insights into the mechanisms of QS inhibitory activity and AI-2 alterations after eugenol treatment.