Final answer:
The microorganism that is both an intracellular parasite and an "energy parasite" is Chlamydia trachomatis, a gram-negative bacterium causing sexually transmitted infections. The correct option is D.
Step-by-step explanation:
The microorganism you are referring to, which is an intracellular parasite and also known as an "energy parasite" due to its inability to produce its own high-energy phosphate compounds, is Chlamydia trachomatis.
Chlamydia trachomatis is a gram-negative bacterium and an obligate intracellular pathogen that relies on host cells for ATP, as it cannot synthesize its own. The life cycle of Chlamydia trachomatis includes a phase where it lives inside the host's cells, making it a significant cause of sexually transmitted infections such as chlamydia.
Therefore, the correct option is D.