Bonds issued under the authority of Sections 65-33-57 and 65-33-59 shall be full faith and credit obligations of the county issuing the same; shall mature within fifteen years of their date of issuance in such annual maturities and denominations as the board of supervisors may direct; shall bear interest at a rate not to exceed five and one half per centum per annum, payable semiannually; may be issued without notice or an election therefor; and shall not be subject to any limitation relative to amount of bonded debt. Such bonds and the interest thereon shall be payable both as to principal and interest from the same sources of revenue and taxes made available for the payment of road protection bonds under the provisions of this chapter. Nothing herein contained shall be construed to affect any of the provisions of House Bill No. 287 [ch. 130] as enacted at the Regular 1938 Session of the Mississippi Legislature.