Section 16. The sheriff shall have custody and control of the jails in his county, and, except in Suffolk county, of the houses of correction therein, and of all prisoners committed thereto, and shall keep the same himself or by his deputy as jailer, superintendent or keeper, and shall be responsible for them. The jailer, superintendent or keeper shall appoint subordinate assistants, employees and officers and shall be responsible for them. In Suffolk county the penal institutions commissioner shall appoint a superintendent of the house of correction, who shall hold office at the pleasure of said commissioner. A sheriff, who acts as jailer, superintendent or keeper, or a jailer, superintendent or keeper appointed by the sheriff, before entering upon the performance of his duties as such, and thereafter, at intervals of not more than one year, so long as he continues so to act or to hold such office, as the case may be, shall give to the state treasurer a bond, with such sureties as the superior court shall order and approve, conditioned faithfully to perform his duties.