LAND USE IMPACT IN POPULATION DYNAMICS OF CULTIVABLE SOIL BACTERIA

Portuguese. Bacteria are one of the main life forms present in soil and are directly affected by its characteristics. Each bacteria community has unique ecological and physiological properties. This makes it possible for them to carry out different processes that occur in soil, such as phosphate solubilization, biological nitrogen fixation, decomposition of organic matter and production of antibiotic compounds. The main goal of this study was to investigate how land use and anthropic activity can interfere in the population dynamics of soil-cultivable bacterial groups. Soil samples were collected from the Ubajara National Park, located in Ubajara, Ceará, Brazil. Sampling was carried out in order to contemplate three different land uses: preserved, conserved and agriculture. The microbial groups used in the research were phosphate solubilizers, nitrogenfixing bacteria and actinobacteria. The abundance of each group was estimated by counting colonies in Petri dishes using the spread plate method. Serial dilutions of 10-3, 10-4, 10-5 and 10-6 were made for each soil sample collected. 0.1 ml of each dilution was spread on Pikovskaya agar medium, Burk's N-free medium and Casein Dextrose Agar culture medium. The plates were incubated at 28°C (± 2) and then colony counts were performed to assess the abundance of these bacteria. Results were expressed as colony forming units (CFU. g-1). Analyzes of variance followed by Tukey's test were performed. contemplating the plots and land uses. Agricultural activity interfered in the population dynamics of functional groups that can be cultivated in the soil.