What would happen if all of the chitin-digesting and cellulose-digesting organisms on the earth were destroyed?

The chitin and cellulose are the structural carbohydrates of the animals and plants. These molecules do not break down spontaneously, but can be digested by organisms such as bacteria. These organisms break down the cellulose and chitin and release the stored carbon in the atmosphere. If these organisms were destroyed, then the carbon will remain accumulated in the dead bodies, and the carbon cycle will be disturbed, and no carbon will be available for the formation of new organisms. Moreover, the dead bodies will start accumulating.