ISSN 2394-9716 International Journal of Novel Research in Interdisciplinary Studies Vol. 4, Issue 4, pp: (1-7), Month: July – August 2017, Available at: www.noveltyjournals.com Page | 1 Novelty Journals Isolation and Characterization of Rhizobia from Rhizospher and Root Nodule of Cowpea, Elephant and Lab Lab Plants 1 Temam Abrar Hamza, 2 Alemayehu Letebo Alebejo 1,2 Department of Biotechnology, College of Natural Sciences, Arba Minch University Abstract: Nitrogen is essential element for plant growth and development which is supplied by mutual symbiosis of rhizobia in cultivated legume plants. Biological nitrogen fixation could help to enhance agricultural productivity and ensure food security. This work aimed isolation and characterization of rhizobia from rhizospher and nodule samples collected from the study area. Isolation of rhizobium were undertaken using Yeast Extract Mannitol Agar medium. A total of 120 rhizobium were isolated from four samples. One isolate from each sample was selected for further characterization. Isolate LLsm1, CPsm1, CPnm1 and Esm1 were found to be negative for MR-VP and starch hydrolysis test. All isolates were found to be positive and negative for catalase and citrate utilization test respectively. They are also found to be Gram negative, rod shaped morphology, fast grower and indole producers. All the isolates were found with poor absorption of Congo red dye and no growth on the YEMA with 2% NaCl. Therefore, all isolates were confirmed as Rhizobia and plant growth promoting bacterial strains. These properties suggest that rhizobium isolated in this study could find potential application for development of the sustainable agriculture as to be a good candidate of biofertilizer which help in soil fertilization without applying chemical fertilizers. Keywords: Rhizobium, Nitrogen Fixing, Bacteria, Isolates, Biofertilizer. 1. INTRODUCTION Microorganisms are living organisms, they are ubiquitous and live in familiar setting such as soil, water, food, and plant roots. Soil microorganisms constitute the world’s largest reservoir of biological diversity and are crucial to the functioning of terrestrial ecosystems. These microbial diversity significantly enhances the rates Carbon and Nitrogen cycle in the ecosystem [1]. They have a profound impact in every facet of human life. The beneficial microbes are fascinating, versatile and carry out extremely useful processes that can’t be achieved by other physical and chemical means [2]. Biological nitrogen fixation is carried out by either symbiotic or free living prokaryotic, it is well documented that biological nitrogen fixation mediated by nitrogennase enzymes is a process important to the biological activity of soil. Soil microorganism that have capacity of fixing nitrogen have frequently been reported as plant growth promoters. A number of microorganisms such as Rhizobium , Blue-green algae (cyanobacteria), Azotobacter, Azospirillum and Clostridium can play significant role in agriculture as Nitrogen fixing microorganisms [3, 4]. Rhizobium are soil microorganism that can live on plant residues (saprophytes) or entirely within plants (endophytes) or (rhizo-bacteria) or in close association with the plant roots [5]. They play a central role in the Nitrogen supply of most soil ecosystems through their ability to fix Nitrogen in symbiosis with legumes. Based on ability to fix nitrogen, rhizobia are classified into slow (Bradyrhizobium) and fast growing rhizobia . The process in which the rhizobia colonize the