All eligible officers and employees of the Georgia Building Authority shall be subject to a merit system of personnel administration as promulgated by the Georgia Building Authority under which all such officers and employees shall be selected on a basis of merit, fitness, and efficiency. All such officers and employees are authorized to become members of the retirement system. There shall be paid from the funds appropriated for the operation of the Georgia Building Authority all contributions required by the retirement system. All such payments shall be in addition to the regular compensation allowed to such officers and employees, provided that membership shall not become effective before March 1, 1956.