FATTY ACID SYNTHESIS IN TAL1000 PEANUT-NODULATING: TEMPERATURE EFFECT

PAULUCCI N; DARDANELLI M; GARCÍA M DE LEMA

Mendoza

Congreso; SAIB; 2012

SAIB

High temperature is known to cause bacterial protein aggregation and denaturation and to cope with this stress factor a cellular response occurs, such as changes in the ratio of unsaturated to saturated (U/S) fatty acids (FA). The aim of this work was to clarify the effect of high temperature on mechanism of monounsaturated fatty acid (MUFA) synthesis in Bradyrhizobium TAL1000. B. TAL1000 was grown in B- medium wih or without radioactive substrates for 16 h at 28°C and shifted to 37°C for 2 h. Cells were harvested, total lipids were extracted (Bligh and Dyer, 1959) and FA methyl esters were prepared using BF in methanol. Non labelled FA were analyzed by GC and labelled FA were separated according to unsaturation degree by AgNO TLC. The radioactivity of each fraction was then quantified. We demonstrate that 18:1 FAdecreased a 45.35%, whereas 18:0 FA increased 41%. Both 19:0 cyclopropane and 20:3 FA increased by heat shock. These changes affected the degree of unsaturation, changing the U/S ratio from 2.77 to 1.27. Also heat shock caused a decrease of 32%, 15% or 30.5% in radioactive recuperation in the MUFA fraction when 18:0 or 16:0 or sodium acetate was the substrate, respectively. The FA desaturarion in B.TAL1000 is down-regulated by temperature to maintain membrane fluidity and a two hour exposure to 37°C is required for a change in the quantity of MUFAto occur.