Dynamic response of the Sinorhizobium meliloti membrane during cyclic temperature changes

PAULUCCIN; CESARI A; REGUERA Y.B.; BIASUTTI ALICIA; DARDANELLI M.S

Buenos Aires

Congreso; LII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2017

SAIB

Sinorhizobium meliloti establish simbiosis with Medicago sativa.The production and storage of inoculants involve suboptimal conditions.Adaptation and survival in many harmful environmental conditionsimplies changes in the dynamics and plasticity of the bacterialmembrane but may affect the symbiotic capacity.In this work, we evaluate how cyclic changes in temperature affectthe viability and phospholipids (PL) composition of Sinorhizobiummeliloti and how these modifications affect the adhesion to alfalfaroots.Culture was grown at 28°C until late exponential phase (control),then it was exposed to: (a) 3 h at 10°C, (b) 3 h at 40°C and (c) 3 hat 10°C. At each stage, an aliquot was taken to assess: the viability(CFU / ml), PL composition, the phase transition temperature (Tm)of the membrane lipid extract (by differential scanning calorimetry)and bacterial adhesion to alfalfa roots (CFU/ml).The viability decreases after stage-(a), increases after stage-(b)and remain constant after stage-(c). The main PLs were phosphatidylcholine(PC), phosphatidylglycerol (PG), phosphatidylethanolamine(PE) and cardiolipin (CL). Exposure (a) resulted in a decreasein PC (34%) and PG (51%) while PE and CL increased (140%and 238%). The same cells submitted to (b) exhibited an inverseresponse (increase of PC and PG and decrease of PE and CL)and after stage-(c), the PL composition was slightly modified. Thevesicles prepared with lipids extracted from control and from cellsat the different stages of the T cycle differed in their Tm (14.8ºC;9.8ºC;14.2ºC;11.8ºC).At the end of stage-(a) a reduction in bacterial adhesion (80%)with respect to the control (100%) was observed. After stage-(b) theadhesion increased 150%, remaining constant after returning to 3hat 10°C (stage-(c)).The successive thermal changes on the same bacterial populationmodifies the PL composition of the cellular envelope and affect itscapacity of early interaction with alfalfa.