In the discretion of the governing authority of any parish issuing its bonds under the provisions of this Sub-part, each or any issue of bonds may be secured by a trust indenture by and between the parish and a corporate trustee, conveying or mortgaging the bridge and pledging the income and revenues thereof in an amount sufficient to pay the principal and interest on the bonds as they severally mature.  

The corporate trustee shall be any trust company or bank having the powers of a trust company within or outside of the state.