Mo. Rev. Stat. § 257.050: Bond for expenses.

At the time of filing the petition, or at any time subsequent thereto and prior to the time of publication of notice of the hearing thereon, a bond shall be filed, with security approved by the court, sufficient to pay the expenses connected with the proceeding prior to a formal decree of the court establishing the district. If at any time during the proceedings the court is satisfied that the bond first executed is insufficient in amount, it may require the execution of an additional bond within a time to be fixed, to be not less than ten days, and upon failure of the petitioners to execute the same, the petition shall be dismissed.