What is the S strain of bacteria about the cause disease in animals but a R strain is not?

The S strain of bacteria is virulent due to its ability to produce a protective capsule that helps it evade the host's immune system, allowing it to cause disease in animals. In contrast, the R strain lacks this capsule and is non-virulent, meaning it cannot effectively evade the immune response and does not cause disease. This difference in pathogenicity is a key factor in understanding bacterial infections and their effects on host organisms.