In traditional BFOA, the elimination-dispersal probability for each bacterium solution is equal . However, that will lose potential Pareto optimal solutions, consequently IBFOA sets elimination-dispersal probability mainly according to the PBM ranks of bacterium, shown as follows: Si=RiRmaxPed,(17) where Rmax is the maximum rank according to PBM, Ri is the rank of bacterium i, Ped is the basic elimination-dispersal probability.