Dynamics of certain $N_2$ fixing bacteria such as Rhizobium, Azospirillum and Azotobactor, nodule number in dominant legume, Atylosia trinervia, P-solubilizing bacteria, actinomycetes and fungi were studied in unburned and burned site of natural grassland, southern India. Population of $N_2$ - fixing bacteria, P-solubilizing bacteria, fungi and nodule number in legume increased significantly in burned sites. On the other hand, the actino-mycetes population remained unchanged. Thirty six species of fungi with tricalcium phosphate solubilizing ability were recorded. The most efficient P-solubilizing fungi recognised in the soils of the study sites are Absidia ramosa, Gongronella butlerii, Mortieralla spinosa, Mucor racemosus, Rhizopus nigricans, R. stolonifer, R. oryzae, Aspergillus fumigatus, A. nidulans, A. niger, Theilavia terricola and Cheatomium lunasporium.