OLIGOTROPHIC BACTERIA IN A SOIL OF THE CALDENAL REGION

This work investigates both the presence and the effect of burning on oligotrophic soil bacteria in a soil of the Caldenal. Two-hundred eigh ty three oligotrophic bacteria were isolated before and after burning the soil and their morphological and physiological characteristics exa mined. Moreover, the resistance to five antibiotics, six heavy metals and three stains in two concentrations was determined. Fire did not re duce the number of oligotrophic bacteria/g soil and neither affected t he types of bacteria that colonized the soil surface (0-5 cm). A high proportion of the isolates were Gram negative non spore forming bacter ia (65 %). All the bacteria were sensitive to brilliant green stain an d resistant to cefuroxime, penicillin G and rifampicin in the highest dosis essayed (20 mu g/ml). Cd and Cu were the most inhibiting heavy m etals. Based on the results obtained the oligotrophic soil bacteria we re classified in eight different collections. The results show that ol igotrophic bacteria are dominant organisms in the biotic structure of the Caldenal soil.