Which new phenomenon did Griffith focus on during his work with pneumonia causing bacteria and mice?

Griffith focused on the phenomenon of transformation during his work with pneumonia-causing bacteria (Streptococcus pneumoniae) and mice. Transformation refers to the process by which bacteria take up DNA from the environment and incorporate it into their genome, resulting in a change in genetic traits. In his experiments, Griffith discovered that when heat-killed bacteria (non-virulent strain) were mixed with live but non-virulent bacteria, the live bacteria could become virulent and cause pneumonia in mice. This indicated that some sort of genetic material from the heat-killed bacteria was being transferred to the live bacteria, enabling them to express the pathogenic traits. Griffith's observation and findings provided early evidence of bacterial transformation and hinted at the existence of a transforming principle, which was later identified as DNA.