Abstract

PEREZ-REYTOR, Diliana Celeste  and  SOSA ESPINOSA, Angela Estela. Assessment of cryopreservation tolerance of two Escherichia coli K12 strains of biotecnology frequent use. Vaccimonitor [online]. 2010, vol.19, n.2, pp.11-17. ISSN 1025-028X.

One of the most recommended methods for E. coli preservation is freezing from -20 ºC to -70 ºC. Glycerol or dymethylsulfoxide as cryoprotectant are commonly used for this purpose. E. coli banks conserved in this way maintain high viability for more than ten years. Though E. coli cryopreservation is a common practice, freezing resistance differences between strains of biotechnological interest are poorly documented. This article compares two mutant strains of E. coli K12, RRI and HB101, in order to evaluate their behavior at both different storage temperatures and glycerol concentrations after eight successive cycles of freezing-thawing. These isolates only differ in their ability to repair DNA damage due to a recA gene mutation in the HB101 variant. When a storage temperature of -70 ºC and different concentrations of cryoprotectant was used the strains showed similar survival after eight cycles. However, the survival behavior differs when the freezing temperatures in the cycles was -20 ºC. In addition to the survival and stability of the genetic markers studied, we observed that the effect of the freezing-thawing cycles delayed their growth on solid medium.

Keywords : Cryoconservation E. coli; freezing-thawing E. coli.

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