In given diagram (A) represents denitrification and (B) represents ammonification. Denitrification is conversion of nitrates into nitrogen gas by some microorganisms e.g., Pseudomonas denitrificans, Thiobacillus denitrificans, Micrococcus denitrificans. Ammonification is conversion of dead remains of living organisms into ammonia with the help of microorganisms like Bacillus ramosus, $B$. vulgaris, $B$. mesentericus etc.