Contamination is rare on plates and morphological characteristics are also as usual Rhizobia but chemical test making me ambiguous. Can you help me by giving any helpful information.
I am culturing on CRYEMA media and I have inoculated at least 20-25 times and subcultured only one isolate got that taken a week and did not grow on 2-3% NaCl. So, it is making me confused that why other isolates are showing different characteristics.
if you are sure that the fast growers are morphologically (colony on CRYEMA) like Bradyrhizobium , better to identify one or two of them by 16S rDNA sequence analysis
16s rRNA gene is a housekeeping gene present in all bacteria. The presence of 16s rRNA gene in an organism confirms that this organism is a bacterium. If I analyze it, then most probably I will get that it is a species of bacteria because the morphological features are more or less same of soil bacteria. But I am concerned about Agrobacterium, it is near about Rhizobia. Moreover, I have tested it by inoculating with new born soybean plant. It made nodules in sand but not in 1% agar medium. My another confusion is that my control replications also produced nodules though I have not input bacterial inoculum.
How I can confirm that it is either Bradyrhizobium or Agrobacterium, do you know about any selection medium that is specific for Rhizobia?