or Restricted Transduction The ability of the bacteriophage to carry only a specific region of the bacterial DNA is called specialized or restricted transduction. demonstrated transformation in Mice using Diplococcus pneumoniae . Two strains of this bacterium are present. One strain produces smooth colonies and are virulent in nature (S-type).
In addition another strain produce rough colonies and are avirulent (R-type). When S-type of cells were injected into the mouse, the mouse died. When R-type of cells were injected, the mouse survived. He injected heat killed S-type cells into the mouse.
The mouse did not die. When the mixture of heat killed S-type cells and R-type cells were injected into the mouse, the mouse died. The avirulent rough strain of Diplococcus had been transformed into S-type cells. The hereditary material of heat killed S-type cells had transformed R-type cell into virulent smooth strains.
Thus the phenomenon of changing the character of one strain by transferring the Figure . : Transduction in Bacteria Phage Phage DNA phage particle particle Recipient Cell Bacterial chromosome Virulent Defective Defective Generalised Transduction Specialised Transduction Figure . : Transformation in Bacteria (a) Griffith’s experiment on Transformation (b) Mechanism of Transformation Mouse lives M li Mouse dies M di Mouse lives M li Mouse dies M di R-Strain Heat-Killed S-Strain killed S- Strain S-Strain R-Strain and Heat- (a) (b) Donar cell Donar DNA Host DNA Recipient cell Integration . .
Economic importance of Bacteria Bacteria are both beneficial and harmful. The beneficial activities of bacteria are given in table . . Table .
: Economic importance of Bacteria Beneficial aspects Bacteria Role . Soil fertility Ammonification . Bacillus ramosus . Bacillus mycoides Convert complex proteins in the dead bodies of plants and animals into ammonia which is later converted into ammonium salt Nitrification .
Nitrobacter . Nitrosomonas Convert ammonium salts into nitrites and nitrates Nitrogen fixation . Azotobacter . Clostridium .
Rhizobium (i) Converting atmospheric nitrogen into organic nitrogen (ii) The nitrogenous compounds are also oxidized to nitrogen (iii) All these activities of bacteria increase soil fertility . Antibiotics . Streptomycin Streptomyces griseus It cures urinary