Inactivation of IAA biosynthesis in Azospirillum brasilense by adding amino acids.

CASSÁN; FABRICIO; RIVERA, DIEGO; MOLINA, ROMINA

Praga

Simposio; International Symposium on Auxins and Cytokinins in Plant Development; 2014

IPGSA

Indole-3-acetic acid (IAA) is one of the most important molecules produced by Azospirillum sp. and is considered to be an important mechanism by which these bacteria promote plant growth and the interaction. Our hypothesis states that both growth and IAA biosynthesis could be regulated by several amino acids. Azospirillum brasilense Az39 was incubated in MMAB minimal medium a temperature of 37 °C to 180 rpm by 24 h. In exponential phase, conditions were standardized, whereby the suspension was centrifuged, washed twice with sterile saline (0,85%) leaving at a DO595: 0,6, and a percentage of inoculum 0,5% v/v was used. Once done, the culture was fractionated with 5 mL in test tubes of 10 mL capacity y was added 100 µg/mL of each of the 6 amino acids individually (L-phe, L-ileu, L-leu, L-val, L-ser, L-ala) by triplicate. Three controls were used (L-trp, L-asp) and distilled water in the same amount. The reaction was allowed to incubate of 120 to 240 minutes; after were evaluated: IAA production (µg/mL), biomass production (OD595) and cellular viability (CFU/mL). The results showed that L-ileu, L-leu, L-val, y L-ala impacted in a decrease in biomass production and significantly (P<0,05) affected the biosynthesis of IAA. However, L-phe, L-ser, only affected the biosynthesis of IAA. These results allow us to understand the mechanisms that would be affected in Azospirillum by the presence of amino acids and also their possible effect on the expression of certain genes that would affect the ability PGPR of the bacteria and the proper development in the interaction with plant.