What characteristic best describes bacteria?

The characteristic that best describes bacteria is that they are single-celled microorganisms with both plant and animal characteristics. Bacteria are prokaryotic organisms, meaning they do not have a nucleus or membrane-bound organelles, which aligns them with the simplicity of single-celled life forms. Some bacteria can perform photosynthesis like plants, while others can obtain their nutrients through processes similar to animals, such as consuming organic material. This versatility allows bacteria to thrive in a wide variety of environments.

Recognizing that bacteria possess traits associated with both kingdoms highlights their diverse metabolic processes and capabilities. This dual characteristic is significant for understanding their ecological roles, ranging from decomposers to pathogens. The other options do not accurately encapsulate the nature of bacteria, as they either misrepresent their cellular structure or suggest classifications that do not apply to bacteria.