Mo. Rev. Stat. § 79.260
Every officer of the city and his assistants, and every alderman, before entering upon the duties of his office, shall take and subscribe to an oath or affirmation before some court of record in the county, or the city clerk, that he possesses all the qualifications prescribed for his office by law; that he will support the Constitution of the United States and of the state of Missouri, the provisions of all laws of this state affecting cities of this class, and the ordinances of the city, and faithfully demean himself while in office; which official oath or affirmation shall be filed with the city clerk. Every officer of the corporation, when required by law or ordinance, shall, within fifteen days after his appointment or election, and before entering upon the discharge of the duties of his office, give bond to the city in such sum and with such sureties as may be designated by ordinance, conditioned upon the faithful performance of his duty, and that he will pay over all moneys belonging to the city, as provided by law, that may come into his hands. If any person elected or appointed to any office shall fail to take and subscribe such oath or affirmation, or to give bond as herein required, his office shall be deemed vacant. For any breach of condition of any such bond, suit may be instituted thereon by the city, or by any person in the name of the city to the use of such person.
§ 79.260, RSMo