“…Several Turing machine simulations by means of polynomial-time uniform families of P systems have been proposed in the literature; some of these apply to unrestricted Turing machines [26,2], while others are limited to machines working in logarithmic space [25], polynomial time [7,6], polynomial space [32,24,17,10,12,13,15,16,14], or exponential space [1]. Most of these solutions [32,24,1,2,7,17,10,12,13,15,6,16,14] are able to simulate Turing machines working in polynomial time with a polynomial slowdown.…”