Tissue P Systems and (Mem)Brane Systems with Mate and Drip Operations Working on Strings

We investigate tissue P systems with (non-restricted, symmetric) versions of mate and drip operations and prove that such systems are computationally complete with the minimal number of two cells when working on strings. Moreover, we consider the variant of scattered context tissue P systems with mate and drip operations and show a similar computational completeness result with using at most four cells during any computation. In all cases, the corresponding results for (mem)brane systems are established, too.