Polyamine involvement in Azospirillum brasilense Az39 biofilm formation

DÍAZ HERRERA SM; GROPPA MD; BENAVIDES MP; ZAWOZNIK MS

Simposio; Frontiers in biosciencie 3; 2018

Among plant growth promoting rhizobacteria (PGPR), Azospirillum brasilense Az39 is a reference strain for inoculants in Argentina, being of great interest the study of its interaction with plants.Considering that the formation of biofilm is one of the first steps of root colonization, the participation of nitrogenous molecules, such as polyamines and nitric oxide was studied.Biofilm formation was measured by crystal violet staining using 96 well plates where the bacteria was grown for 3 days without agitation at 30 °C and subjected to different treatments. Initially, polyamines were used as the only N source in the culture medium. Then, biofilm formation was studied upon the addition of increasing putrescine concentrations to the complete medium. In addition, inhibitors of polyamine biosynthesis (DL-α- (Difluoromethyl) arginine (DFMA) and DL-α- (Difluoromethyl) ornithine (DFMO), and MGBG) were also studied. To analyze if nitric oxide was involved in the observed responses, biofilm formation was also measured after the addition of SNP and GSNO (NO donors) and cPTIO (NO scavenger).The results obtained so far allow us to conclude that the use of polyamines as the only source of N significantly increases biofilm formation, possibly in response to the stress produced by the lower availability of this nutrient. Polyamines biosynthesis inhibitors negatively affected the biofilm, indicating the involvement of these compounds on its formation. However, the exogenous addition of Put presented different results according to the concentration used, which would indicate a fine regulation of this response. The use of NO-generating compounds, as well as cPTIO, showed that this molecule would affect biofilm formation.