RRB Paramedical Staff Nurse Model Paper 4

Griffith considered two different strains of the bacterium Streptococcus pneumoniae - S strain and R strain. The former is pathogenic\/virulent and can cause the disease, while the latter is non-pathogenic\/nonvirulent and cannot cause the disease. Heat-killed S strain bacteria however, lose their virulence and become non-pathogenic. R strain bacteria in general, don’t need to be heat-killed as they are already non-pathogenic.