Behaviour of Bradyrhizobium SEMIA6144 membrane during adaptation to water deficit

CESARI A.B; REGUERA Y.B; PAULUCCI N.S; KILMURRAY C; DARDANELLI M.S.

Córdoba

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology FINAL 7 nov 2016; 2016

The membrane lipid bilayer is one of the primary cellular targets affected by variations in medium osmolarity, which cause changes influidity that may exert negative effects. We evaluate the behavior of the membrane ofBradyrhizobiumSEMIA6144 during adaptationto polyethylene glycol (PEG). B. SEMIA6144 was exposed to growth and PEG shock. A fluidizing effect on the membrane wasobserved 10 min after shock; however, the bacteria were able to restore optimal fluidity. This rapid response (1 h) was mediated by anincrease in lysophosphatidylethanolamine from phosphatidylethanolamine and an increase in saturated fatty acids, resulting in greatermembrane rigidity. When the cells were exposed to shock for 5 h and 24 h, the amount of lysophosphatidylethanolamine decreasedwhile phosphatidylethanolamine increased. This phospholipid turnover was associated with elevated phospholipase A activity after 1 hof shock. Membrane fluidity of cells grown with PEG was also equal to that of the control; however, the response was an increase inphosphatidylcholine at the expense of phosphatidylethanolamine, and an increase in levels of unsaturated fatty acids.We conclude thatduring PEG shock, the membrane composition of B. SEMIA6144 is rapidly remodeled to counter fluidizing effect; then, this responseis dynamically modified by process that involves phospholipid and acyl chain turnover.