Phenotypic and molecular characterization of diazotrophic bacteria associated with sugarcane in Bangladesh

The study was conducted with the intent to isolate and characterize endophytic and diazotrophic bacteria from stem and roots of sugarcane (Saccharum sp.) and from associated rhizosphere with a wider goal to develop bio-fertilizer. Twenty-one samples of bacteria were isolated from sugarcane samples obtained from the test field of Bangladesh Sugarcane Research Institute (BSRI), Pabna, and from cultivation field of Ruppur, Bangladesh. Out of 21 isolates, 11 were identified as members of the class Gammaproteobacteria (with one exception) and majority of them were Enterobacteriaceae. The isolates were characterized by determining their metabolic characteristics, stress factor tolerance, plant growth-promoting attributes, and molecular characteristics. The isolates were phenotypically diverse, retaining some characteristics of Enterobacteriaceae. A significant number of isolates produced indole acetic acid and iron-chelator siderophore. Majority of them also solubilized phosphorus. Among molecular characteristics, the nifH gene region of Enterobacteriaceae family was detected by PCR amplification. The PCR products of 16S rRNA and nifH gene of representative isolates were sequenced and phylogenetically analyzed. This study establishes that a significant percentage of the bacteria found in the sugarcane stem, root, and associated rhizosphere has the potential to fix atmospheric nitrogen and promote plant growth. Therefore, they may have the feasibility to be used as bio-fertilizer.