Universality of Splicing Test Tube Systems with Two Tubes

Splicing test tube systems are one of the first distributed computing models based on splicing. The model introduces (test) tubes where the splicing operation is applied, which are arranged in a communication network with filters that permits to redistribute the words between the tubes at each step. We show that the computational completeness can be achieved with two tubes when the communication graph does not have self-loops. We also construct a universal splicing test tube system with 2 tubes having 23 rules.