Which of the following bacteria could exhibit phototaxis?

• A. Staphylococcus aureus
• B. Rhodospirillum rubrum
• C. Clostridium botulinum
• D. Escherichia coli

Answer: (B)

Verified step by step guidance

1. Understand the concept of phototaxis: it is the movement of an organism toward or away from a light source, commonly seen in photosynthetic bacteria that use light as an energy source.
2. Identify which bacteria among the options are photosynthetic or have the ability to respond to light stimuli. Phototactic behavior is typically found in bacteria that perform photosynthesis or have light-sensitive mechanisms.
3. Analyze each option: Staphylococcus aureus is a non-photosynthetic, Gram-positive cocci; Clostridium botulinum is an anaerobic, spore-forming bacterium without photosynthetic ability; Escherichia coli is a facultative anaerobe and does not perform photosynthesis.
4. Recognize that Rhodospirillum rubrum is a photosynthetic bacterium belonging to the purple non-sulfur bacteria group, known for its ability to move toward light sources, thus exhibiting phototaxis.
5. Conclude that among the given options, Rhodospirillum rubrum is the bacterium capable of phototaxis due to its photosynthetic nature and motility mechanisms responsive to light.