In reproduction operation, half of the optimal bacteria reproduce their offspring. Specially, we rank each bacterium according to PBM and half of bacteria with poor ranking reproduce. Assuming that every component in bacteria is independent with each other, and follow the Gaussian distribution, the reproduction operation presented as follows: Qt+1=ηnormσt+μt,(15) ηnorm=−2lnη1cos(2πη2),(16) where η1 and η2 are the uniformly distributed random number in interval [0, 1], the formula generating ηnorm is called BOX-Muller formula, μt, σt are the mean and standard deviation of the element in each position of the bacteria generated in iteration t and before.