Spacetime structure and unification of fundamental interactions

I discuss the problem to what extent fundamental interactions determine the structure of spacetime. I show that when we are using only topological methods the spacetime should be modelled on an R-compact space. Demanding the existence of a differential structure substantially narrows the choice of possible models but the differential structure may not be unique. I also show by using the noncommutative geometry construction of the standard model that fundamental interactions determine the spacetime in the class of R-compact spaces. Fermions are essential for the process of determining the spacetime structure.