The kind of organisms able to grow aerobically on slants or at the top of thioglycollate tubes are called facultative anaerobes and obligate aerobes. Facultative anaerobes are able to function with or without oxygen. In the presence of oxygen, they are able to produce ATP through aerobic respiration. Otherwise, they shift to fermentation or anaerobic respiration. On the other hand, obligate aerobes are organisms that strictly require the presence of oxygen in order to live and grow.
