Effect of UV-irradiation on the Species Diversity of Culturable Heterotrophic Bacteria from Paddy Field Soil

The effect of moderate UV-irradiation (45J/m2) on species diversity of asporogenic heterotrophic bacterial isolates from paddy field soil was studied. Although the isolates from irradiated Petri dishes had less pronounced hydrolytic abilities and eutrophs were less numerous, irradiation did not result in specific selection of UV-resistant bacteria. Species diversity indices were higher for the set of isolates from irradiated dishes. This can be due to the fact that the number of cells inoculated onto irradiated dishes was about one hundred higher than onto control dishes; there may be a greater chance for soil bacteria of minor groups to form isolated colonies on irradiated dishes.