The various departments, institutions, boards, bureaus, or agencies of the state, except for the Department of Agriculture, which is provided for in Code Section 50-19-3, are authorized, subject to the appropriation of funds for such purposes, to purchase passenger-carrying automobiles and other motor vehicles for the use of officers, officials, and employees in the performance of their official duties. The operation, use, maintenance, service, and repair of passenger-carrying automobiles shall be governed by the rules and regulations promulgated by the Department of Administrative Services pursuant to Code Section 50-19-1, except as otherwise provided by law.