Sharon,

Similar research works have been done on several plants other than Piper longum. Please have a look at these links and PDF attacchment.

http://www.sciencedirect.com/science/article/pii/S0944501304001028

https://www.researchgate.net/publication/236104284_Nitrogen-fixing_bacteria_with_multiple_plant_growth-promoting_activities_enhance_growth_of_tomato_and_red_pepper

http://www.sciencedirect.com/science/article/pii/S094450131300089X

Good luck

Article Nitrogen-fixing bacteria with multiple plant growth-promotin...

Thank you for the immediate responce sir...i have gone through this articles i want in piper longum

Dear Emeemal Sharon,

Thanks for your question.Your objective to isolate & identification nitrogen fixing bacteria, that you isolate from rhizosphere soil of pepper.Any way your target to get nitrogen fixing bacteria.So you can first dilution of serial dilution of soil , then spread on nitrogen free media.Nitrogen fixing bacteria may be free living or symbiotic.for Rhizobia you can use CRYEMA media.After incubation you pick up desire colony bacteria.then perform some biochemical test.I hope you fillup your target.Best of luck.