show Abstracthide AbstractWe analyzed RNA-Seq data of two Staphylococcus aureus strains, Newman and SH1000, infected by Kayvirus phage K. Staphylococcus virus K is used in the phage therapy, its genome is 148 kb long consisting of dsDNA with long terminal repeats, and encodes 233 ORFs and 4 tRNAs. The sampling times 0, 2, 5, 10, 20, and 30 minutes after infection were chosen based on the growth characteristics of the phage K at the two S. aureus strains. From the RNA-Seq data we determined transcriptional profile of the phage K and its hosts, which allowed us to identify differentially expressed genes, ncRNAs, and promotor and terminator sites. Transcription of the phage K genes starts immediately after the infection of bacterial cells and we found a gradual take-over by phage K transcripts in the infected cells. The temporal transcriptional profile of phage K was similar in both strains and the relative expression of phage K genes shows three distinct transcript types – early, middle, and late based on the time they reach maximum expression. The bacterial response to phage K infection is similar to the general stress response. It includes the upregulation of nucleotide, amino acid and energy synthesis and transporter genes and the downregulation of transcription factors. The expression of particular virulence genes involved in adhesion and immune system evasion as well as prophage integrases were marginally affected. This work unveils the versatile nature of phage K infection leading to its broad host range Overall design: Infection of two S. aureus strains, SH1000 and Newman, with Staphylococcus virus K sampled in biological triplicates at 0, 2, 5, 10, 20, and 30 minutes after infection.