In an experiment, a microbiologist put equal numbers of each of the following organisms into a flask of sterile broth, consisting mostly of sugar and a few amino acids. She then placed the flask in the dark. Which of the organisms would be most likely to survive?

• A. Cyanobacteria
• B. Photoheterotrophs
• C. Thermoacidophilic bacteria
• D. Photoautotrophs
• E. Chemoheterotrophic bacteria

Answer: (E)

Verified step by step guidance

1. Identify the nutritional requirements of each organism type listed in the problem. Cyanobacteria and photoautotrophs require light for photosynthesis, while photoheterotrophs also rely on light but use organic compounds as a carbon source. Thermoacidophilic bacteria thrive in acidic and high-temperature environments, often using inorganic substances for energy.
2. Consider the conditions provided in the experiment: the flask is placed in the dark, and the broth contains sugar and amino acids. This environment lacks light, which is essential for organisms that rely on photosynthesis.
3. Evaluate which organisms can survive without light. Chemoheterotrophic bacteria do not require light for energy; they obtain energy by consuming organic compounds, such as sugars and amino acids, which are present in the broth.
4. Understand that chemoheterotrophic bacteria are well-suited to the conditions of the experiment because they can metabolize the available organic compounds in the dark, unlike the other organisms that require light.
5. Conclude that chemoheterotrophic bacteria are the most likely to survive in the given conditions, as they can utilize the sugar and amino acids in the broth for energy and growth without the need for light.