Transcriptome analysis reveals the tetracycline resistance mechanism of Lacticaseibacillus rhamnosus FXJWS19L2 and Lacticaseibacillus paracasei FQHXN23L6

Abstract

Lacticaseibacillus rhamnosus and Lacticaseibacillus paracasei are widely used and regularly consumed probiotics. However, before they are used in food, safety evaluation of antibiotic resistance should be performed to assess the risk of transferring resistance genes. Our study found that L. rhamnosus FXJWS19L2 and L. paracasei FQHXN23L6 exhibited a high tetracycline resistance phenotype but did not contain any known tetracycline resistance genes in their genomes. To investigate the molecular mechanisms underlying tetracycline resistance in these two strains, we performed a transcriptomic analysis combined with gene overexpression techniques to explore potential resistance genes and validate their functions. The transcriptome analysis identified 963 and 372 differentially expressed genes (DEGs) in L. rhamnosus FXJWS19L2 and L. paracasei FQHXN23L6, respectively, after tetracycline induction. The DEGs in these two strains were mainly involved in ribosomal protein synthesis, ABC transporters, and the metabolism of many substances. Moreover, the overexpression of the most significantly up-regulated gene (yjcA), which encodes an ABC transporter, improved the resistance of bacteria to tetracycline. This study reveals the resistance mechanism of these two strains to tetracycline and provides a theoretical reference for the safe application of this type of lactic acid bacteria in food.