Isolation, characterization and identification of nitrogen fixing bacteria with organic fertilizer applications in paddy soil

Abstract

The high organic matter content allows soil microbial activity to recycle organic matter, which is essential for life, such as the nitrogen cycle. The process of biological nitrogen fixation by microorganisms is crucial for nitrogen entry into the nitrogen cycle. This study aims to isolate and characterize nitrogen-fixing bacteria in paddy soil using organic fertilization applications. This study was conducted in Salassae Village, Bulukumba, South Sulawesi, Laboratory of Microbiology, Soil Science Department, Hasanuddi University. This research method is a descriptive study using morphological Characterization, biochemical tests, and molecular identification. This study succeeded in isolating ten nitrogen-fixing bacterial isolates from wetland soil samples using organic fertilizers. Morphological characterization results showed quite different results in terms of color, size, shape, and level. The highest nitrogen-fixing ability test was obtained in isolates. L1.P, where the highest nitrogen fixation ability was 0.26%. Biochemical Characterization using VITEK®. 02 shows that almost all biochemical tests show a positive reaction. The identification of Nitrogen-fixing bacteria species using 16S rRNA gene sequencing showed that L1.P was identified with 99% similarity to Bacillus subtilis subsp. subtillis str. 168.