Adaptational Changes in Lipids of Bradyrhizobium SEMIA 6144 Nodulating Peanut as a Response to Growth Temperature and Salinity

Abstract

Phospholipids provide the membrane with its barrier function and play a role in a variety ofprocesses in the bacterial cell, as responding to environmental changes. The aim of the present study wasto characterize the physiological and metabolic response of Bradyrhizobium SEMIA 6144 to saline andtemperature stress. This study provides metabolic and compositional evidence that nodulating peanutBradyrhizobium SEMIA 6144 is able to synthesize fatty acids, to incorporate them into its phospholipids(PL), and then modify them in response to stress conditions such as temperature and salinity. The fattyacids were formed from [1-14C]acetate and mostly incorporated in PL (95%). Phosphatidylcholine (PC),phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL) were found to be themajor phospholipids in the bacteria analyzed. The amount and the labeling of each individual PL wasincreased by NaCl, while they were decreased by temperature stress. The amount of PC, PE, and PGunder the combined stresses decreased, as in the temperature effect. The results indicate that synthesizedPL of Bradyrhizobium SEMIA 6144 are modified under the tested conditions. Because in all conditionstested the PC amount was always modified and PC was the major PL, we suggest that this PL may beinvolved in the bacteria response to environmental conditions.