Before entering upon the duties of his office, each of said commissioners shall take and subscribe to the oath of office as prescribed in this Constitution and shall, in addition thereto, swear that he is not, directly or indirectly, interested in any railroad, street railway, traction line, canal, steam boat, pipe line, car line, sleeping car line, car association, express line, telephone or telegraph line, nor in the bonds, stocks, mortgages, securities, contract or earnings of any railroad, street railway, traction line, canal, steam boat, pipe line, car line, sleeping car line, car association, express line, telephone or telegraph line; and that he will, to the best of his ability, faithfully and justly execute and enforce the provisions of this Constitution, and all the laws of this State concerning railroads, street railways, traction lines, canals, steam boats, pipe lines, car lines, sleeping car lines, car associations, express lines, telephone and telegraph lines, compress and elevator companies, and all other corporations over which said Commission has jurisdiction, which oath shall be filed with the Secretary of State.