Jari Ojala SICS / NNRC

What are protozoa?

Eucaryotic cells (cells with a nucleus) are among the most sophisticated cells found in nature [Alberts B., Bray D., Lewis J., Raff M., Roberts K. and Watson J. D., 1994]. Eucaryotic cells are the building blocks of animals and higher plants from single-celled protozoa to large mammals. Protozoa are complex single-celled animals (Figure 1), which have large variety of different forms and behaviours [Sleigh M. A., 1989]. In [Alberts B., Bray D., Lewis J., Raff M., Roberts K. and Watson J. D., 1994] is a good description of protist (single-celled animals) and protozoa:

Their anatomy is often complex and includes such structures as sensory bristles, photoreceptors, flagella, leglike appendages, mouth parts, stinging parts and musclelike contractile bundles. Although they are single cells, protists, especially the larger and more active types known as protozoa, can be as intricate and versatile as many multicellular organisms.

Figure 1. A protozoan; a single-celled animal

The nucleus of the protozoan contains mostly deoxyribonucleic acids (DNA). Ribonucleic acids (RNA) are messenger molecules between the nucleus and the cytoplasm, where most cell's chemical reactions occur. DNA acts mostly as a storage for the genetic information and RNA forms proteins in the cytoplasm based on this information. The proteins created in cytoplasm form the body, the sensor and the actuator organelles of the cell.

When the sensors of the protozoan detect food, the actuators move the cell in a way that the food is obtained. How does this ``protozoa control'' work? One theory of this interaction is to think that sensor organelles catalyse (speed up) the formation of some substance, say A. This substance A then catalyses/inhibits the formation of a substance B etc. Finally a substance, say Z, boosts the metabolism of the actuator organelles, which causes the protozoan to move. There is a complex and parallel molecular interaction pathway from the sensors to the actuators: sensor-organelles,A,B,..parallel interactions..,Z,actuator-organelles. My protozoa inspired robot control research tries to construct a simple model for this ``protein computer''. I hope to use this artificial protozoa theory to control an autonomous robot.

Some preliminary results

The following animation shows a snake-like mobile robot controlled by the artificial protozoa model. The snake tries to learn to move forward by using only the friction between the snake and the platform to propell itself. This specific movement style was found using the genetic algorithm.

Snake-like mobile robot, (MPEG, 223Kb)

Please adjust the frame-rate of your mpeg-viewer if the snake moves too fast.

Online documents related to my protozoa research

WWW protozoa pointers

References

Alberts B., Bray D., Lewis J., Raff M., Roberts K. and Watson J. D., Molecular biology of the cell, third edition, Garland Publishing, Inc., New York, 1994.

Sleigh M. A., Protozoa and other protists. Edward Arnold, London, 1989.

Contact information:

Jari Ojala
RWCP Novel Functions SICS Laboratory
P.O.Box 1263
S-164 28 KISTA
Sweden
Tel: +46 8 752 1500
Fax: +46 8 751 7230
E-mail: ojala@sics.se

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