Contracts authorized by this chapter shall not be let to any person, association of persons, firm, company or corporation, connected, directly or indirectly, with any combination in the form of an unlawful trust in restraint of trade, or who has an understanding, directly or indirectly, to limit, in any manner, competition in bidding upon the construction of any state road or bridge, or for furnishing any materials. Any such combination or unlawful trust is hereby forbidden. Any person, association of persons, firm or corporation entering into, or being a part of, any such combination or unlawful trust shall be guilty of a misdemeanor, and, upon conviction thereof, shall be fined not exceeding $1,000; and every person, county or state officer, or any employee of any county of the state, or of the state road commissioner or other person connected therewith, directly or indirectly, and any officer or member of a corporation, who shall be engaged in any way in promoting any such combination or unlawful trust, or in aiding or abetting the same, or knowingly committing any acts in pursuance thereof, in addition to being subject to the fine aforesaid, may, in the discretion of the court, be imprisoned not exceeding six months.