The exercise of the powers conferred by this article constitute the performance of essential governmental functions, and as bridges which are owned and operated by municipalities constitute public property used for public purposes, such bridges shall at all times be free from taxation within the state. No municipality shall be required to pay taxes or assessments upon any such bridge or any part thereof owned by it, whether located within or without the corporate limits of such municipality, and bonds issued under the provisions of this article, their transfer, and the income therefrom (including any profits made on the sale thereof) shall at all times be free from taxation within the state.