"Bacterial" refers to anything related to bacteria, which are tiny, single-celled organisms found almost everywhere on Earth. They can live in soil, water, and even inside the bodies of plants and animals. While some bacteria can cause diseases, many are beneficial and play essential roles in processes like digestion and nutrient cycling. Bacteria are incredibly diverse, with thousands of different species. For example, E. coli is a common bacterium found in the intestines of humans and animals, helping with digestion. On the other hand, Streptococcus can cause throat infections. Understanding bacteria is crucial for fields like medicine and environmental science.