Are black holes responsible for giving a galaxy its shape?
Supermassive black holes are responsible for the evolution of galaxies.
It is know accepted that every large galaxy, including out Milky Way galaxy, has a supermassive black hole at its centre.
Recent observations have shown that there is a relationship between the mass of the supermassive black hole and the mass of the galaxy containing it. The bigger the galaxy, the bigger the black hole.
It is now thought that the supermassive black hole controls star formation in the galaxy. The black hole emits "winds" of gases into the galaxy. These winds change the distribution of gasses within the galaxy which can clear the gases from star forming regions and stop star formation.