Which of the following statements about bacteria is true?

The statement that bacteria can exist in various environments is accurate. Bacteria are incredibly versatile organisms that can thrive in a wide range of conditions, including extreme environments where most other living organisms would struggle to survive. This includes places like hot springs, deep-sea vents, acidic lakes, and even within the human body. Their ability to adapt to different conditions is part of what makes them so prevalent and vital in many ecological systems.

Other statements do not accurately represent bacteria. For instance, while some bacteria can be harmful and are associated with diseases, many are beneficial and play essential roles in processes like digestion, nutrient cycling, and even in biotechnology. Furthermore, not all bacteria require oxygen; some are anaerobic and can survive without it. Lastly, bacteria are primarily unicellular, meaning they consist of a single cell, distinguishing them from multi-cellular organisms.