The officers of said Village shall consist of three trustees who shall constitute the Board of Trustees, three water commissioners who shall constitute the Board of Water Commissioners, three electric light commissioners who shall constitute the Board of Electric Light Commissioners, a Chief Engineer, and First and Second Assistant Engineers, a Clerk, Treasurer, Collector, and an Auditor, all of which officers shall be chosen by ballot; except the Assistant Engineers, who shall be appointed by the Chief Engineer. Said officers shall be elected for the term of one year, except the members of the Board of Trustees, the Board of Water Commissioners, and the Board of Electric Light Commissioners, who shall be elected for the term of three years, and until their successors are elected.