1. Ahmad F, Ahmad I, Khan MS (2005) Indole acetic acid production by the indigenous isolates of Azotobacter and fluorescent Pseudomonas in the presence and absence of tryptophan. Turkish J Biol 29:29–34
2. Alexander M (1991) Introduction to soil microbiology. Krieger, NY, USA, 467p
3. Baldani JI, Krieg NR, Baldani VLD, Hartmannand A, Dobereiner J (2005) Genus II. Azospirillum. In: Brenner DJ, Krieg NR, Staley JT (eds) Bergey's manual of systematic bacteriology, vol 2C. Springer, New York, USA, pp 7–26
4. Bashan Y, de-Bashan LE (2010) How the plant growth-promoting bacterium Azospirillum promotes plant growth—a critical assessment. Adv Agron 108:77–136
5. Bhaduri S, Demchick PH (1983) Simple and rapid method for disruption of bacteria for protein studies. Applied Environmental Microbiology 46:941–943