Miss. Code § 77-5-125
Whenever a district shall, by resolution of its board, determine that it is in the public interest and in the interest of efficient and economical operation of a utility to alter the territorial limits of a district, it shall so order and certified copies of such order shall be filed with the secretary of state, the clerk of each municipality in the district and the clerk of the board of supervisors of each county in which any portion of the district is located. Thereupon the territorial limits of a district shall be considered altered in accordance with such order. However, any territory added to a district must be coterminous with an election unit or units. No additional territory may be added to a district except upon the petition of not less than one-third (1/3) of the qualified voters residing therein, certified as provided in Section 77-5-109. The order of the board hereinabove referred to shall contain a statement of the number and percentage of such petitioners, if any. In the event the boundaries of any election unit or units are changed subsequent to the creation of a district, then the whole of any election unit, any part of which was theretofore within the district, shall automatically become a part of said district.
Miss. Code § 77-5-125