Complexity Generates Robustness in Bacterial Heat Shock Response

Prof. Hiroyuki Kurata, Department of Biochemical Engineering and Science, Kyushu Institute of Technology

In the heat shock response, s32 (encoded the rpoH gene) plays a major role in controlling expression of the genes of the heat shock proteins (chaperones and proteases). The level of active s32 is regulated by complex mechanisms: chaperone-mediated regulation of s32 activity and stability, thermoregulated-induction of the rpoH mRNA, and protease-mediated degradation of s32. The numerical framework model shows that complexity in s32 regulation generates robustness in the E. coli heat shock response, thereby increasing the robustness of the interconnected factors among subsystems. A complex network seems to impede isolating a smaller subsystem out of a whole biological system. However, complexity generates robustness of the heat shock response, thereby making it possible to extract such a subsystem out of the whole system and analyze it separately. A biological system may be a collective body of mosaic-like subsystems rather than a melting pot of subsystems.