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In 2000, Gardner and Collins reported the construction of a fundamental genetic regulatory device, the bi-stable toggle switch, in E. coli. We report here our work on a natural extension of this powerful device, a tri-stable genetic toggle switch capable of switching among three stable states. Like the bi-stable switch, the tri-stable switch consists of repressible promoters that produce inhibitory proteins and requires only a transient pulse of chemical inducer to switch among stable states. Our proof-of-principal construct is designed to control the expression of three different fluorescent reporters using the pBad/AraC, pLacI/LacI, and pTetR/TetR systems; though a tri-stable switch can theoretically be constructed from any three repressible promoters that satisfy a certain mathematical relationship. We have modelled the system extensively, creating both a simple continuous deterministic model based on the work of Gardner and Collins (Gardner and Collins, 2000) and a more complex discrete stochastic model based on the work of Isaacs (Isaacs, 2003). The tri-stable switch, designed, modelled, and partially constructed as an iGEM 2006 project at Brown University, is to be composed entirely of Biobricked parts from the Registry of Standard Biological Parts. In addition to providing support for the iGEM hypothesis, the tri-stable toggle switch has implications for biotechnology and gene therapy.

Tardigrades inhabiting terrestrial environments exhibit extraordinary resistance to ionizing radiation and UV radiation although little is known about the mechanisms underlying the resistance. We found that the terrestrial tardigrade Ramazzottius varieornatus is able to tolerate massive doses of UVC irradiation by both being protected from forming UVC-induced thymine dimers in DNA in a desiccated, anhydrobiotic state as well as repairing the dimers that do form in the hydrated animals. In R. varieornatus accumulation of thymine dimers in DNA induced by irradiation with 2.5 kJ/m(2) of UVC radiation disappeared 18 h after the exposure when the animals were exposed to fluorescent light but not in the dark. Much higher UV radiation tolerance was observed in desiccated anhydrobiotic R. varieornatus compared to hydrated specimens of this species. On the other hand, the freshwater tardigrade species Hypsibius dujardini that was used as control, showed much weaker tolerance to UVC radiation than R. varieornatus, and it did not contain a putative phrA gene sequence. The anhydrobiotes of R. varieornatus accumulated much less UVC-induced thymine dimers in DNA than hydrated one. It suggests that anhydrobiosis efficiently avoids DNA damage accumulation in R. varieornatus and confers better UV radiation tolerance on this species. Thus we propose that UV radiation tolerance in tardigrades is due to the both high capacities of DNA damage repair and DNA protection, a two-pronged survival strategy.

A persistent presence in space can either be supported from Earth or generate the required resources for human survival from material already present in space, so called "in situ material." Likely, many of these resources such as water or oxygen can best be liberated from in situ material by conventional physical and chemical processes. However, there is one critical resource required for human life that can only be produced in quantity by biological processes: high-protein food. Here, recent data concerning the materials available on the Moon and common asteroid types is reviewed with regard to the necessary materials to support the production of food from material in situ to those environments. These materials and their suitability as feedstock for the biological production of food are reviewed in a broad and general way such that terminology that is often a barrier to understanding such material by interdisciplinary readers is avoided. The waste products available as in situ materials for feasibility studies on the International Space Station are also briefly discussed. The conclusion is that food production in space environments from in situ material proven to exist there is quite feasible.

Scenesence is the decline of cellular function that accompanies ageing. A reduced diet has been shown to increase longevity in many organisms including mice, rats, monkeys and fruit flies. This increase in longevity is also linked to reduced metabolic activity and in particular reduced production of insulin. Here we investigate the reduction of an insulin-like peptide that is caused by decreasing the amount of yeast fed to larval and adult fruit flies. The peptide is found in the brain and can be identified and measured by antibody staining and then visualized under a confocal microscope. This produces a stack of images which can then be labeled, and from this a three dimensional model showing insulin quantity, vesicle size and location can be produced. Quantifying insulin production in this way and measuring its responsiveness to diet will enable us to better model the functions of genes acting upstream and downstream of the insulin peptide and the insulin cell surface receptors. from BioSysBio: Bioinformatics and Systems Biology Conference Edinburgh, UK, 14–15 July 2005