From 2007.igem.org

Freeze-Drying Device

Bactoblood needs the ability to be stored for long periods in a freeze-dried form so that it can be stockpiled and easily transported. We therefore sought a genetic device that could improve the Bactoblood's structural integrity during dessication. We designed two distinct desiccation devices: one that utilizes the disaccharide trehalose and one that involves the small molecule hydroxyectoine.

Trehalose

The genes in the trehalose biosynthesis pathway are pulled right out of the E.coli genome and consist of otsA and otsB. By overexpressing these genes after bactoblood has reached saturation, the can protect itself from damage during freeze drying without having to add exogenous protectants. OtsB encodes for a 29.1-kDa trehalose-6-phosphate phosphatase and otsA encodes for a 53.6-kDa trehalose-6-phosphate synthase. Together they make up a trehalose-6-phosphate synthase/phosphatase complex. Naturally, the 3' end of the otsB coding region overlaps the 5' end of the otsA coding region by 23 nucleotides. The Trehalose helps the frozen dehydrated cells to recover back to a functioning hydrated state. Not all cells survive the freeze drying process but Trehalose increases the rate of success.

 

Hydroxyectoine

The hydroxyectoine biosynthesis pathway present in Streptomyces Chyrsomallus consists of four genes: thpA, thpB, thpC and thpD. In our system, we plan on The other three genes are there to initiate the process. When inserted into a bacterium, hydroxyectoine will prevent dessication and many other extremes. It will protect the bacteria's proteins and cell membrane.

Lyophilization

The image above demonstrates that trehalose stabilizes the cell's lipid membrane and prevents leakage upon rehydration.

 

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