Azospirillum brasilense responds to water deficit adjusting lipid composition to maintain membrane fluidity

CESARI A; REGUERA Y; PAULUCCI N; KILMURRAY C; DARDANELLI M

Mar del Plata

Congreso; Congreso; 51 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2015

SAIB

Azospirillum is a rhizobacteria studied for its ability to improve growth and performance of many crop by alleviating stresses.We studied A. brasilense tolerance to water deficit and the dynamics of adaptive process at the membrane level.A. brasilense was exposed to polyethylene glycol 15 mM (PEG) growth and PEG shock (10, 20, 30 and 60 min). Membrane fluidity was determined by measuring fluorescence polarization of DPH. Lipids were extracted. The fatty acids (FA) were analyzed by GC. Identification of phospholipids (PL) was performed using TLC. For its quantification, [1-14C] sodium acetate was added to culture.A. brasilense viability was reduced in presence of PEG. Cells grown with PEG showed membrane fluidity similar to those grown without. Lipid composition was modified, increasing phosphatidylcholine and decreasing phosphatidylethanolamine amounts. The unsaturation FA degree was reduced. The fluidity decrease 20 min after the addition of PEG, indicating that the PEG has a fluidizing membrane effect. Fluidity returned to initial values after 60 min of PEG exposure.We conclude that A. brasilense perceive osmotic changes by changing membrane fluidity. This effect is offset by changes in PL and FA composition, contributing to the homeostasis of membrane fluidity under water deficit. This knowledge can be used to develop new A. brasilense formulations applied to water deficit.