Gene map of the sea virulence region of S. aureus. Gene map of the sea gene and regions immediately upstream and downstream of the gene in six different S. aureus strains. The map is based on nucleotide sequence analysis of the strains. Solid lines are sequences within the sea-carrying prophage. Dotted lines represent sequences outside the prophage region. The letters a-h indicates were PCR amplicons are located within the region; numbers 1-2 indicate transcription start sites .