Survival and Development of Photosynthetic Oxygenic Organisms Tolerant to Space Radiation and Production of Compounds with Anti-Oxidant Properties

The Photo experiments on board Foton-M2 satellite

Photo-I integrated on the Biopan-5 facility on board Foton-M2 spacecraft

Photo-I filled with biological samples before the integration on Foton-M2

Photo-II integrated inside the Foton-M2 capsule

On 31st May 2005 at 14:00 (CEST), the satellite Foton-M2 was launched from the Cosmodrome of Baikonour (Kazakhstan). The capsule came back to Earth on 16th June at 9:37 (CEST), after 16 days spent in space, along an orbit with an inclination of 63 and a mean altitude of ~280 km. Among the experiments carried on board there were Photo-I and Photo-II, dedicated to the understanding the response of oxygenic photosynthetic organisms to space as an extreme environment.

In this section only Photo-I experiment will be described in detail. Photo-II was sent in space even with the following Foton-M3 mission: the description of this experiment can be found in the Web page dedicated to Photo-II in Foton-M3.

The Photo-I experiment: the hardware

The Photo-I hardware. In each of the 16 holes a biological sample was deposited. The container was sealed and it was equipped with a set of pass band filters to obtain different visible and UV light conditions above the samples

Photo-I is a passive experiment i.e. no measurements were performed in real-time during the exposure to the space environment- constitued by a sterile container 56x53x25 mm3 able to host different biological samples in 16 cells (or small wells). The mass of the device is of the order of 100g and can host dozens of grams of biological content. Each one of the cells was covered using a combination of four pass wavebands filters with a transmittance from 1% to 10%, to test the samples under different visible and UV light conditions. Then, during the experiment most of the cells were kept nearly in the dark -the solar light intensity that reached the samples had an average value of 2 mol photons m-2 s-1 and they were fully exposed to space radiation. Photo-I was integrated on the Biopan-5 facility, a seashell-like container mounted outside the Foton capsule and dedicated to experiments which need direct exposure to the space environment. Biopan was opened once the satellite reached its orbit and was closed 351 hours later, just before the re-entry of the capusle to Earth. The temperature of Photo experiment was controlled during the flight, mantaining in the range 5C to 25C.

The Photo-I experiment in the Biopan facility

The Photo-I experiment: the biological samples tested in space

Four different set of mutants of the unicellular green alga Chlamydomonas reinhardtii were inserted into the Photo module (the reference strain IL -a mutant without introns in the psbA gene encoding for the D1 protein- and pools of several D1 mutants). In the 16 positions available each set was exposed to four different conditions regarding the quality and the intensity of visible and UV radiation.
The algae were integrated into Photo in Florence, in the labortory of the Institute of Ecosystem Study-National Research Council. A defined quantity of algae was filled into each of the 16 cells on top of solid TAP medium. On TAP medium C. reinhardtii can grow photoautotrophically as well as heterotrophically because it contains acetate as carbon and energy source.
In Florence rubber seals and glass filters were inserted and finally the plate with the tinted quartz filters was attached. Packed in this way and under permanent light exposure by a white LEDs panel, the algae were transported to Noordwijk (Netherlands) ESTEC centre of the European Space Agency. Here they were wrapped with aluminium foil and integrated into the Biopan platform. After installing the module, the platform was transported via Samara to Baikonur.

The measurements carried out on the samples

After the re-entry of the Foton capsule to Earth, Biopan was transported to the ESTEC centre of the European Space Agency in Noordwijk (The Netherlands) where it was opened. Then, the Photo-I module was transported to laboratory where any visible modifications or damages were orbserved. Here, the algae were suspended in TAP medium and let grow up for 2 weeks, when the survived colonies started to become visible.
The screening to evaluate the tolerance of the strains to the space raditions was based on the following approaches and analyses:
- Vitality, evaluated measuring the PSII fluorescence;
- Cell cultures (media, inoculum);
- Protein Extraction, Western Blotting, data on D1 integrity and protein turnover;
- site-directed PCR for psbA gene amplification, sequence comparison analysis.