Such civil service commission, by and with the advice of the chief of each department, shall have disciplinary control and supervision over the employees of the fire department and the police department of such city and may employ, promote and discharge employees thereof, except that the chiefs of the fire, police and detective departments shall be elected by the commission and confirmed or approved by city council. The commission shall make and enforce all such rules and regulations as may be deemed necessary in the exercise of their duties and powers and establish and fix the requirements of applicants for employment therein.