FATTY ACIDS PATTERN IN RHIZOBIUM PEANUT NODULANT: ROLE IN HYPERTERMIA AND SALINITY.

PAULUCCI N; MEDEOT D; MEYER J; BUENO M; GARCÍA M

Mar del Plata

Congreso; XLIII SAIB; 2007

SAIB

Most microorganisms adapt their membrane lipid composition to environmental changes in order to stabilize the fluidity of the membranes, using cis-trans isomerization on unsatured fatty acids (FA) or modifying the saturated to unsatured FA ratio. We have studied in this work the effect of temperature and salt concentration on the viability and FA composition of Rhizobium TAL 1000. The strain was grown under control conditions (28ºC), hypersalinity (0,3 M NaCl), hyperthermia (37ºC) and hyperthermia-hypersalinity ( 37ºC+0,3 M NaCl ). Cells were harvested, total lipids were extracted and FA methyl esters were prepared using BF3 in methanol. FA analysis was performed using GC. Rhizobium TAL 1000 was able to grow in the presence of 0,3 M NaCl or at 37ºC. The viability decreased under salinity. However, there were not differences when the strain was exposed to the combination of both stresses. The detected FA were octadecenoic (18:1), octadecanoic (18:0), hexadecanoic (16:0) and a FA of twenty carbon atoms, probably eicosatrienoic, (20:3) as major FA. All FA were affected by temperature, being the most relevant fact a decrease of 18:1 (87%) and an increase of saturated FA (100%). The FA composition of Rhizobium TAL 1000 resembles to that described for other rhizobia. FA of this strain were modified in response to temperature changes in order to survive under adverse conditions.