The commissioner shall be qualified by training and experience to direct the work of the bureau. The commissioner shall be appointed by the governor, by and with the advice and consent of the senate, and shall serve at the pleasure of the governor. A vacancy occurring in the office of the commissioner shall be filled in the same manner as the original appointment. The commissioner shall devote his entire time and attention to the duties of his office and shall not be engaged in any other profession or occupation. He shall receive a salary as provided by annual appropriation.