2.6.2. Indole Acetic Acid (IAA) Production Assay
For assessment of IAA, archaeal cultures were inoculated in 100 mL sterile MGM broth containing 0.1% L-tryptophan and the flasks were kept in shaking incubator at 120 rpm, 37 ℃ for 7 days. The culture medium was transferred to sterile falcon tubes and centrifuged at 10,000 rpm for 15-20 minutes. The supernatant was transferred to a flask and pH was adjusted at 2.8 using hydrochloric acid. Later, it was extracted twice with equal volumes of ethyl acetate. The clear solution was transferred to a beaker and anhydrous sodium sulfate was added to absorb left over moisture. The clear solution was evaporated until dry using rotary evaporator and was resuspended in 1 mL methanol. These samples were analyzed by high-performance liquid chromatography (HPLC; Waters; e2995, separations module) with 299h photodiode-array (PDA) detector using a Nucleosil C18 column (4.6×250 mm, 3μM; Macherey-Nagel, Germany). The mobile phase was a mixture of methanol/acetic acid/water (30:1:70, v/v/v) and the flow rate was adjusted at 1.2 mL/min. Pure indole-3- acetic acid (Sigma) was used to prepare standard solutions and IAA production was quantified.