PURPOSE: To purify microbes without affecting the ecosystem in the open system environment such as polluted soil, an oil outflow area or the like by using microbes provided with pollutant decomposition activity in which natural decay is derivated under specified conditions.

CONSTITUTION: Microbes having pollutant decomposition activity and also natural decay protein forming activity are dispersed in an area to be purified to purify the environment, and then the temperature of the environment is changed to the given derivation temperature to destroy the microbes. The microbes are the environment purifying microbes having a vector in which structural genes coding for enzymes decomposing a pollutant are incorporated and another vector 3 in which structural genes 2 coding for natural decay protein and a promotor sequence 1 for developing the structural genes are incorporated, and the vectors are taken into the microbes having the structural genes coding for a developing substance for turning over the direction of the promotor sequence by heat.