We show that tissue P systems with symport/antiport having 3 cells and symport/antiport rules of minimal weight generate all
recursively enumerable sets of numbers. Constructed systems simulate register machines and have purely deterministic behaviour.
Moreover, only 2 symport rules are used and all symbols of any system are present in finite number of copies (except for symbols
corresponding to registers of the machine). At the end of the article some open problems are formulated.