The bonds may be secured by a trust indenture by and between the corporation and a corporate trustee which may be any bank having the power of a trust company or any trust company within or without the state. Such trust indenture may contain such provisions for protecting and enforcing the rights and remedies of the bondholders as may be reasonable and proper and not in violation of law, including covenants setting forth the duties of the corporation in relation to the exercise of its powers and the custody, safekeeping, and application of all money. The corporation may provide by the trust indenture for the payment of the proceeds of the bonds and revenue to the trustee under the trust indenture or other depository, and for the method of disbursement thereof, with such safeguards and restrictions as the corporation may determine. All expenses incurred in carrying out the trust indenture may be treated as a part of the operating expenses of the corporation. If the bond shall be secured by a trust indenture, the bondholders shall have no authority to appoint a separate trustee to represent them.