Final answer:
Clostridium sporogenes, an anaerobic bacterium, would not grow on an oxygen-rich medium but is likely to grow in a fluid thioglycollate medium, where reduced oxygen levels provide a favorable environment for such microbes.
Step-by-step explanation:
Clostridium sporogenes is a gram-positive, anaerobic, spore-forming bacterium that is not expected to grow on an aerobic general-purpose medium. The lack of growth could be due to the oxygen-rich environment of the plate which is lethal to anaerobic bacteria like C. sporogenes. The failure to grow indicates that C. sporogenes requires an anaerobic environment, and therefore, would likely grow in a fluid thioglycollate medium which is designed to promote the growth of anaerobic and microaerophilic bacteria.
Thioglycollate medium contains reducing agents such as thioglycollic acid that lower the oxidation-reduction potential and remove oxygen. When the medium is freshly prepared and autoclaved, most of the oxygen is driven out. As a microaerophile, which requires low levels of oxygen for growth, C. sporogenes would be expected to grow just below the surface of the medium where the oxygen concentration is suitable for its growth but not at the top, which would be too oxygen-rich, nor the bottom, which would be completely void of oxygen.