(1) Except as provided in subsection (2) of this section, every bidder, before entering on work pursuant to contract, shall give bond to the county with at least two good and sufficient sureties, who shall be residents of the state, and one of whom shall be a resident of the county, in any sum not less than one thousand dollars, and in such additional amount as the county board may require, which bond shall be approved by the county board and shall be conditioned for the faithful execution of the contract. The county board may accept or may require a surety bond in like amount and conditioned the same as the personal bond prescribed in this section.

(2) If a contract, the provisions of which are limited to the purchase of supplies or materials, is entered into pursuant to this section and if the amount of the contract is fifty thousand dollars or less, the bidder shall furnish the county with an irrevocable letter of credit, a certified check upon a solvent bank, or a performance bond in a guaranty company qualified to do business in Nebraska, as prescribed by and in an amount determined by the county board, conditioned for the faithful performance of such contract.