International Research Journal of Biotechnology (ISSN: 2141-5153) Vol. 4(7) pp. 117-123, August, 2013. DOI: http:/        
Copyright © 2013 International Research Journals


Full Length Research Paper

Isolation and characterization of Rhizobium spp. and determination of their potency for growth factor production

†Sk. Md. Jakaria Al-Mujahidy1, Md. Mehedi Hassan1, 2*, Md. Mizanur Rahman1,  and  A. N. M. Mamun-Or-Rashid1

1Department of Biotechnology and Genetic Engineering, Islamic University, Kushtia-7003, Bangladesh

2Department of Microbiology and Genetics; and Institute for Medical Science, Chonbuk National University Medical School, Jeonju 561-712, South Korea.

*Corresponding Author Email: Tel: +821058402229.

†These authors have equal contribution



The most important step of this study was to isolate Rhizobium species and determination of their potency for growth factor production. We isolated 260 type bacteria on PCA (Plate Count Agar) media from adjacent soil samples of ten leguminous plants, two non-leguminous plants and control soil (without plant). Then pure cultures of 53 nitrogen fixing bacterial strains were isolated on selective Yeast Extract Mannitol Agar (YEMA) medium. Five isolates (Ma-G1, Ch-H2, Lo-F1, Sh-J1and Ra-I2) were selected as Rhizobium hainanense and better result was regarded in their assessment for production potency of various growth factors. All Rhizobium spp. were able to fix nitrogen in media. Among these isolates, indole acetic acid (IAA) was produced by Ma-G1 and Ra-I2. The exopolysaccharide production rate of Ma-G1 was enhanced expectedly (1.25-fold increase) by treating with IAA. Unfortunately, these five strains were unable to separate soluble phosphorus content from insoluble tri-calcium phosphate (TCP). High salt tolerance was also observed by all strains in media supplemented with IAA containing 5-10% KH2PO4.Therefore, this Rhizobium spp. would be the beneficial bacteria to interplay with the growth promotion of leguminous plants along with biological nitrogen fixation.

Keywords: Leguminous plants, Rhizobium hainanense, growth factor production, biological nitrogen fixation.