Short communication Resistance of a recombinant Escherichia coli to dehydration Galina Khroustalyova a , Joseph Boudrant b , Alexander Rapoport a, * a Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Kronvald Blvd., 4, LV-1586 Riga, Latvia b Laboratory of Chemical Engineering Science, UPR CNRS 6811, Nancy-Universite ´, INPL, Vandoeuvre-les-Nancy, France Received 14 December 2008; revised 26 May 2009; accepted 25 July 2009 Abstract Dehydration of microorganisms, rendering them anhydrobiotic, is often an efficient method for the short and long term conservation of different strain-producers. However, some biotechnologically important recombinant bacterial strains are extremely sensitive to conventional treatment. We describe appropriate conditions during dehydration of the recombinant Escherichia coli strain HB 101 (GAPDH) that can result dry cells having a w88% viability on rehydration. The methods entails air-drying after addition of 100 mM trehalose to the cultivation medium or distilled water (for short term incubation). Ó 2009 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved. Keywords: Escherichia coli; Recombinant strain; Cell resistance; Anhydrobiosis; Dehydration; Rehydration 1. Introduction Desiccation is a natural stress to which different microor- ganisms are frequently subjected. Apart from their theoretical interest, the mechanisms of microbial cell survival under extremely dry conditions merit investigation because the resistance of bacterial cells to dehydration is very important in biotechnology. All the factors that can influence cell sensi- tivity and stability must be clearly understood to establish new, simple and effective methods for ensuring the short and long term conservation of strain-producers without significant loss of their physiological characteristics. The possibility of conserving genetically engineered strains in the dry state needs special attention where they have been found extremely sensitive to dehydration. This investigation attempted to establish a successful method getting such bacteria into an anhydrobiotic state. 2. Materials and methods 2.1. Bacterial strain and media Escherichia coli HB 101 (GAPDH) was stored in 15% glycerol at 80  C (see Gscheadler et al., 1994). It was grown aerobically in M2 media overnight at 37  C on a rotary shaker at 200 rpm. Trehalose (Sigma) was added at 100 mM to either the culture medium or distilled water for fermentation or incubation, respectively. 2.2. Dehydration and plate count of cells Cells were harvested at stationary phase and in some experiments incubated with trehalose at 37  C for 40 min, dehydrated for 16 h at 30  C before being resuspended in 20 ml M2 medium without glucose. The plates were inoculated in triplicate for each dilution step and incubated at 30  C for 2 days before CFUs were counted to determine viability. The results are presented as the mean values of triplicate assays. 3. Results In an initial determination of the resistance to dehydration of this bacterial, the highest viability was w16%, which is too * Corresponding author. Tel.: þ371 67034891; fax: þ371 67034885. E-mail address: rapoport@mail.eunet.lv (A. Rapoport). 1065-6995/$ - see front matter Ó 2009 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.cellbi.2009.07.001 Cell Biology International 33 (2009) 1194e1195 www.elsevier.com/locate/cellbi