The computational model of membrane computing (formalized through membrane systems, also called P systems) is based on the way that biological membranes define compartments, each having its set of molecules and (enzymes enhancing) reactions, with compartments communicating through the transport of molecules through membranes. In this paper we augment the basic model of membrane systems with promoters and inhibitors, which formalize the reaction enhancing and reaction prohibiting roles of various substances (molecules) present in cells. We formalize such membrane systems with promoters/inhibitors and investigate their basic properties. In particular we establish universality results, i.e., we provide characterizations of recursively enumerable sets (of vectors of natural numbers) using these systems. It turns out that systems with promoters/inhibitors achieve universal computations without using the standard “auxiliary” features of membrane systems, for instance, without using catalysts.
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