| Non-symbiotic diazotrophic bacteria are amongst the most important functional groups of soil-dwelling microorganisms. These bacteria contribute to plant growth predominantly through biological N2 fixation. Here, we evaluated the density and diversity of non-symbiotic diazotrophic bacteria in soils taken from diverse land use systems (LUS) in Amazonia using nitrogen-free media. A total of 30 soil samples were collected from the following LUS: pristine forest, young secondary forest, old secondary forest, agroforestry, agriculture and pasture. Bacterial density was evaluated by the most probable number (MPN) method utilizing N-free semi-solid media with varied compositions (JNFb, NFb, LGI and Fam). Individual isolates were characterized by colony and... |
