Characterization of Streptomyces spp. Producing Indole-3-acetic acid as Biostimulant Agent

Abstract

Twenty six isolates of Streptomyces spp. obtained from Cyperus rotundus L. rhizosphere were tested for ability to produce indole-3-acetic acid (IAA) in yeast malt extract (YM) medium containing 2 mg/mL tryptophan. Screening of the isolates for ability to produce IAA was carried out by adding Salkowski reagent in bacteria culture and was measured quantitatively by spectrophotometer at λ 530 nm. Thin Layer Chromatography (TLC) method was used to determine IAA. To ensure the IAA production in Streptomyces isolates, gene involved in IAA biosynthesis was detected by amplifying Tryptophan Monooxigenase (iaaM) gene. The study of the effect of tryptophan on the production of IAA was measured at different concentrations of tryptophan (0, 1, 2, 3, 4, 5 mg/mL) in the bacterial culture. The result showed that there were two Streptomyces spp. isolates which could produce IAA, namely the isolates of Streptomyces sp. MS1 (125.48 μg/mL) and Streptomyces sp. BR27 (104.13 μg/mL). The TLC result showed that the compound in both isolates was identifi ed to be IAA. The amplifi cation results showed that iaaM gene was detected in both isolates. This results indicated that the IAM pathway is predicted involved in the biosynthesis of IAA in the selected isolates. Both of the isolates were able to produce IAA after 24 h incubation and the highest production was at 120 h incubation with the concentration of tryptophan was 2 mg/mL dan 1 mg/mL, respectively. Therefore, it is concluded that Streptomyces spp. isolates are able to produce IAA and potentially to be utilized as biostimulat agent.

Screening and characterization of actinomycetes isolated from soybean rhizosphere for promoting plant growth

“…In this study, isolate ASR 67 was the highest IAA producer with a concentration of 30.6 mg/L in the medium supplemented with 0.1 mg/mL L-tryptophan. De Fretes et al (2013) reported that Streptomyces sp. strain MS1 isolated from rhizosphere soils was able to produce IAA with a concentration of 120 mg/L in the 2 mg/mL L-tryptophan supplemented medium.…”

Response of Tagetes patula L. and Ageratum houstonianum Mill. to Microbial Biostimulant Inoculation and Organic Fertilization

“…Research on fungi and bacteria suggests that the mixtures of microorganisms work complementarily in a biostimulant consortium [84] and determine a synergic interaction by providing nutrients, removing inhibitory products, and stimulating beneficial physiological traits [85]. Among the bacteria, Agrobacterium radiobacter, Bacillus subtilis and Streptomyces have in common many effects: they secrete plant growth promoting substances such as phytohormones [86][87][88], proline [89], vitamins, and antifungal metabolites, improve zinc and phosphate solubilization [90][91][92] and Fe mobilization [93] in vitro and in soil, even under abiotic stress conditions [18,94,95]. Organic fertilization effectively increases soil bacteria [96], while mineral fertilization reduces soil bacterial network complexity and connectivity [97].…”

Relief from Salt Stress by Plant Growth-Promoting Bacteria in Hydroponic Leaf Lettuce (Lactuca sativa L.)

“…Micrococcus yunnanensis [14], Micrococcus luteus [15], dan Streptomyces sp., [16]. This microorganism was tolerant to salty water.…”

“…The color shift was detected at a wavelength of 530 nm and recorded the absorption. The first day of fermentation is considered day 0 [16]. The findings of bacterial IAA production optimization are used to estimate the production age of the inoculum before it is fed to the hydroponic installation.…”