Submitted to: Microbiome
Publication Type: Abstract Only
Publication Acceptance Date: 4/14/2022
Publication Date: N/A
Technical Abstract: The impact of Salmonella enterica infection in cattle may be highly variable and is often serovar-dependent. The aim of this study was to compare the global transcriptomes of the highly pathogenic bovine-adapted S. Dublin and the less pathogenic bovine-adapted S. Cerro during interactions with bovine epithelial cells to identify genetic features that impact serovar-related outcomes of S. enterica infections in dairy animals. Bovine mammary epithelial cells, MAC-T, were infected with Dublin and Cerro strains (two strains of each serovar). Bacterial RNA was extracted using a differential lysis method and host RNA contaminants were removed using the MICROBEnrich kit. RNA-Seq libraries were prepared using a TruSeq Stranded mRNA Library Prep kit and sequencing was conducted on an Illumina NextSeq500 sequencer for 2 × 151 cycles. The total number of paired-end reads that uniquely mapped to non-rRNA and non-tRNA genomic features in the S. enterica reference genomes ranged between 12.1 M and 23.4 M. In total, 360 differentially expressed genes (DEGs) were identified with at-least 2-fold differences in the transcript abundances between the two serovars (FDR = 5%). Sixty three of the 360 (17.5%) DEGs were located in the genomic regions that are potential Salmonella Pathogenicity Islands (SPIs). The SPI-genes that were upregulated (' 2-fold) in the Dublin strains compared to the Cerro strains included 37 (of 44) SPI-1 genes encoding mostly the T3SS apparatus and effectors, all of the SPI-4 genes encoding T1SS (siiABCDEF), T3SS effectors and chaperon (sopB, pipB, and sigE) located in SPI-5, the T4SS associated protein coding genes (sciJKNOR) located in SPI-6, and T3SS effector sopF in SPI-11. Major functional categories of DEGs included transcriptional regulators (n = 25), amino acid metabolism (n = 20), carbohydrate metabolism (n = 20), energy production (n = 19), cell membrane biogenesis (n = 18), coenzyme transport and metabolism (n = 15), and prophage associated genes (n = 14). DEGs were further mapped to the metabolic pathways listed in the KEGG database and most genes of the fatty acid ß-oxidation pathway were upregulated/uniquely present in the Dublin strains compared with the Cerro strains. This study identified signatures in the global transcriptomes of two S. enterica serovars that may be responsible for serovar-related differential interactions between S. enterica and the bovine epithelial cells. Results from this study may be used to identify interventions that can reduce colonization, and infection of S. enterica in dairy animals.