In any general health district the board of health may, upon the recommendation of the health commissioner, appoint for full or part time service a public health nurse and a clerk and such additional public health nurses, physicians, and other persons as are necessary for the proper conduct of its work. Such number of public health nurses may be employed as is necessary to provide adequate public health nursing service to all parts of the district. Employees of the board, other than the commissioner, shall be in the classified service of the state, and all employees of the board may be removed for cause by a majority of the board.