摘要：In this paper we focus on two weak forms of cooperation in P systems,
namely, catalytic rules and matter/anti-matter annihilation rules.
These variants of P systems both are computationally complete,
while the corresponding rule complexity turns out to be of special interest.
For establishing considerably small universal P systems in both cases,
we found two suitable tools: generalized register machines and generalized counter automata. Depending on the features used in the different variants, we construct several small universal P systems.
