Self-extension model of slime mold’s allorecognition behaviour (Vol. 49 No.5-6)

Two typical encounter cases of Physarum rigidum (plasmodium). They can recognize an encounter as self or non-self and decide to fuse (a) or avoid (b) allogeneic individuals.

When slime molds encounter an allogeneic individual, they judge whether to fuse or avoid it. This decision can be made without coming in contact with each other.

Slime molds move, feed, and grow during single-celled amoeboid stage—plasmodium. They can divide into multiple individuals and fuse. In this study on Physarum rigidum, an interesting behaviour was observed when they encountered an allogeneic individual. The plasmodia stopped their movement, came in contact with each other at the cell membrane surface, and then decided their actions. If they judge the encounter can become “self”, they fused, and if they recognize it as “non-self”, they avoided each other. This allorecognition behaviour can sometimes take several hours. More importantly, this behaviour can occur without contact between cell membranes. It is impressive to observe plasmodia stay apart from each other and decide their behaviour. In our study, we clarified that this behaviour, i.e., non-contact allorecognition, occurs with the spread of slime sheath, which is hyaline mucus secreted by plasmodium. Plasmodium diffuses slime sheath as an information substance of “self” to the environment, and it can be called "self-extension".

M. Masui, S. Satoh and K. Seto, Allorecognition behaviour of slime mold plasmodium—Physarum rigidum slime sheath-mediated self-extension model, J. Phys. D: Appl. Phys. 51, 284001 (2018)