This special issue “Contributions to Membrane Computing” includes revised and expended versions of four of the best membrane computing papers presented at the Workshop on Membrane Computing 2015 (Dinneen 2015) and the International Conference on Unconventional Computation and Natural Computation 2015 (Calude and Dinneen 2015) held in Auckland, New Zealand from 31 August to 4 September 2015. We have selected four extended papers (out of six invited and reviewed) for this special issue. These are listed and briefly described below.

The paper “Extended Spiking Neural P Systems with White Hole Rules and Their Red-Green Variants” by Artiom Alhazov, Rudolf Freund, Sergiu Ivanov, Marion Oswald and Sergey Verlan shows that an extended model of neural P systems are Turing complete and after adding further colored extensions allow to go beyond Turing.

The paper “A Uniform Family of Tissue P Systems with Protein on Cells Solving 3-Coloring in Linear Time” by A. Hepzibah Christinal, Daniel Díaz-Pernil and T. Mathu introduces a model of tissue P systems protein communications and highlights this with a linear-time solution of the classic NP-complete 3-coloring problem.

The paper “Some New Results of P Colonies with Bounded Parameters” by Luděk Cienciala and Lucie Ciencialová investigates the abstract computing P colonies model and summarizes the computational power with bounded number of agents and programs. New results are provided for homogeneous P colonies with capacity two and one.

The paper “On Simulating Cooperative Transition P Systems in Evolution-Communication P Systems with Energy” by Richelle Ann B. Juayong and Henry N. Adorna studies energy-based evolution-communication P systems with cooperative rule triggers. In their constructed ECPe systems, a transition in the TP system is simulated by a k-step computation where k is a factor of the alphabet size in the original system.