The ability of anhydrobiotic organisms (or "anhydro-organisms") to withstand desiccation, and the remarkable stability they then display in the dried state, would potentially be very useful if it could be applied to otherwise desiccation-sensitive cells. We have therefore attempted to perform anhydrobiotic engineering on several model cell types.
Gram-negative bacteria such as Escherichia coli and Pseudomonas putida are normally considered sensitive to desiccation, but when pre-conditioned by growth in hypersaline media and dried under vacuum from suspension in desiccation protectants, they can exhibit excellent desiccation tolerance. Survival of 50-80% of control values can be obtained, and then maintained for at least six weeks at above ambient temperatures.
Attempts to achieve similar desiccation tolerance in mammalian cells have been unsuccessful, however. Biosynthesis of the non-reducing disaccharide trehalose has been implicated in anhydrobiosis in several organisms, but genetic engineering of mammalian cells to enable them to produce this sugar did not increase desiccation tolerance, although improved osmotolerance was observed. We are currently assessing other factors which could be required for anhydrobiotic engineering of mammalian cells. In the meantime, we are beginning to learn more about what happens to human cells when dehydrated and have shown that signalling pathways governed by key regulatory proteins (MAPKs) are activated. A number of genes are also upregulated, suggesting that human cells can sense and respond to desiccation.
Anhydrobiotic Engineering Research Topics:
Garcia de Castro, A., Bredholt, H., Strøm, A. R. and Tunnacliffe, A. (2000) Anhydrobiotic engineering of gram-negative bacteria. Appl. Environ. Microbiol. 66: 4142-4144.
Bullifent, H. L., Dhaliwal, K., Howells, A. M., Goan, K., Griffin, K., Lindsay, C. D., Tunnacliffe, A. and Titball, R. W. (2000) Stabilisation of Salmonella vaccine vectors by the induction of trehalose biosynthesis. Vaccine 19: 1239-1245.
Garcia de Castro, A. and Tunnacliffe, A. (2000) Intracellular trehalose improves osmotolerance but not desiccation tolerance in mammalian cells. FEBS Lett. 487: 199-202.
Tunnacliffe, A., Garcia de Castro, A. and Manzanera, M. (2001) Anhydrobiotic engineering of bacterial and mammalian cells: is intracellular trehalose sufficient? Cryobiology 43: 124-132.
Howells, A.M., Bullifent, H. L., Dhaliwal, K., Griffin, K., Garcia de Castro, A., Frith, G., Tunnacliffe, A. and Titball, R. W. (2002) Role of trehalose biosynthesis in environmental survival and virulence of Salmonella enterica serovar typhimurium. Res. Microbiol. 153: 281-287.
Manzanera, M., Garcia de Castro, A., Tøndervik, A., Rayner-Brandes, M., Strøm, A. R. and Tunnacliffe, A. (2002) Hydroxyectoine is superior to trehalose for anhydrobiotic engineering of Pseudomonas putida KT2440. Appl. Environ. Microbiol. 68: 4328-4333.
Manzanera, M., Vilchez, S. and Tunnacliffe, A. (2004) High survival and stability rates of Escherichia coli dried in hydroxyectoine. FEMS Microbiol. Lett. 233: 347-352.
Manzanera, M., Vilchez, S. and Tunnacliffe, A. (2004) Plastic encapsulation of stabilised Escherichia coli and Pseudomonas putida. Appl. Environ. Microbiol. 70: 3143-3145.
Huang, Z. and Tunnacliffe, A. (2004) Response of human cells to desiccation: comparison with hyperosmotic response. J. Physiol. 558: 181-191.
Vilchez, S., Tunnacliffe, A. and Manzanera, M.(2008) Tolerance of plastic-encapsulated Pseudomonas putida KT2440 to chemical stress. Extremophiles. 12: 297-299.