After 24 hours of growth, this image depicts four different agar media culture plates that had been inoculated with Shigella sp., Escherichia sp., and Proteus sp. bacteria, (clockwise: MacConkey, Shigella-Salmonella, Bismuth Sulfite, and Brilliant Green agars).

Differences in the constituents, which compose the various agar media, are used as determinants as to which bacteria are fostered on each culture plate. Thriving culture colonies on one type of medium may not thrive on another type of medium based on the agars’ ingredients, which a given bacterium will require to maintain life.

Image source: Centers for Disease Control and Prevention Publich Health Image Library.

本图片是美国卫生及公共服务部旗下的美国疾病控制与预防中心的作品，系有关雇员作为其公务目的所拍摄或制作。作为美国联邦政府的作品，本图片属于公有领域。