What is it about?

We investigated the conditions for the optimal preservation of P. putida KT2440 and its derivatives for long-term storage. The highest survival rates were achieved with cells that had reached the stationary phase and which had been subjected to freeze-drying in the presence of disaccharides (trehalose, maltose, and lactose) as lyoprotectants. Using fluorescence polarization techniques, we show that cell membranes of KT2440 were more rigid in the stationary phase than in the exponential phase of growth. This is consistent with the fact that cells grown in the stationary phase exhibited a higher proportion of C17:cyclopropane as a fatty acid than cells in the exponential phase. Mutants for the cfaB gene, which encodes the main C17:cyclopropane synthase, and for the cfaA gene, which encodes a minor C17:cyclopropane synthase, were constructed. These mutants were more sensitive to freeze-drying than wild-type cells, particularly the mutant with a knockout in the cfaB gene that produced less than 2% of the amount of C17:cyclopropane produced by the parental strain.

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Why is it important?

Pseudomonas putida KT2440, a saprophytic soil bacterium that colonizes the plant root, is a suitable microorganism for the removal of pollutants and a stable host for foreign genes used in biotransformation processes. Because of its potential use in agriculture and industry it is important dilucidate optimal conditions for preservation and genes implicated in the survival of this bacterium to freeze-drying.

Perspectives

In short, our results indicate that cyclopropane fatty acids are important in P. putida KT2440 for survival in freeze-drying processes and that the highest survival rates in this strain are achieved with disaccharides as lyoprotectants. In the near future we plan to perform detailed transcriptional studies of cfa synthesis in different genetic backgrounds.

Ph. D. Jesús Munoz-Rojas
Benemerita Universidad Autonoma de Puebla

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This page is a summary of: Involvement of Cyclopropane Fatty Acids in the Response of Pseudomonas putida KT2440 to Freeze-Drying, Applied and Environmental Microbiology, January 2006, ASM Journals,
DOI: 10.1128/aem.72.1.472-477.2006.
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