Biomolecular Characterization of Diazotrophs Isolated from the Tropical Soil in Malaysia

International Journal of Molecular Sciences

Umme Aminun Naher²  Radziah Othman²  Mohammad Abdul Latif³  Qurban Ali Panhwar¹  Puteri Aminatulhawa Megat Amaddin¹ 

[1] Department of Land Management, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; E-Mails:;Institute of Tropical Agriculture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia; E-Mails:;Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh; E-Mail:

关键词: diazotrophs;    nitrogenase enzyme activity;    indoleacetic acid;    scanning electron microscopy;    transmission electron microscopy;    16S rRNA;   

DOI  :  10.3390/ijms140917812

来源: mdpi

【 摘 要 】

This study was conducted to evaluate selected biomolecular characteristics of rice root-associated diazotrophs isolated from the Tanjong Karang rice irrigation project area of Malaysia. Soil and rice plant samples were collected from seven soil series belonging to order Inceptisol (USDA soil taxonomy). A total of 38 diazotrophs were isolated using a nitrogen-free medium. The biochemical properties of the isolated bacteria, such as nitrogenase activity, indoleacetic acid (IAA) production and sugar utilization, were measured. According to a cluster analysis of Jaccard’s similarity coefficients, the genetic similarities among the isolated diazotrophs ranged from 10% to 100%. A dendogram constructed using the unweighted pair-group method with arithmetic mean (UPGMA) showed that the isolated diazotrophs clustered into 12 groups. The genomic DNA rep-PCR data were subjected to a principal component analysis, and the first four principal components (PC) accounted for 52.46% of the total variation among the 38 diazotrophs. The 10 diazotrophs that tested highly positive in the acetylene reduction assay (ARA) were identified as Bacillus spp. (9 diazotrophs) and Burkholderia sp. (Sb16) using the partial 16S rRNA gene sequence analysis. In the analysis of the biochemical characteristics, three principal components were accounted for approximately 85% of the total variation among the identified diazotrophs. The examination of root colonization using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) proved that two of the isolated diazotrophs (Sb16 and Sb26) were able to colonize the surface and interior of rice roots and fixed 22%–24% of the total tissue nitrogen from the atmosphere. In general, the tropical soils (Inceptisols) of the Tanjong Karang rice irrigation project area in Malaysia harbor a diverse group of diazotrophs that exhibit a large variation of biomolecular characteristics.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland