EN
9,10-methylenehexadecanoic acid was found to be the main and sole constituent of the cyclopropane fatty acid (CFA) pool of five Pseudomonas fluorescent strains. Our findings have shown that all the studied isolates of plant-growth promoting rhizospheral fluorescent pseudomonads have qualitatively identical CFA profiles, even though they have the ability to make use of distinct carbon sources and show different plant root colonisation ability. This report suggests that the preservation of the proper CFA composition in biomembranes may be crucial for rhizobacteria adaptation to the fluctuation of physicochemical conditions in the rhizosphere.