The term 'rod-shaped bacterium' refers to two specific types of bacteria, BACILLUS and E. COLI. BACILLUS is a genus of Gram-positive, rod-shaped bacteria that are found in soil and water. They are known for their ability to form endospores, which allow them to survive in harsh environments. E. COLI is a Gram-negative, rod-shaped bacterium that is commonly found in the intestines of humans and other warm-blooded animals. It is an important part of the human microbiome and is used in many scientific studies. Both BACILLUS and E. COLI are rod-shaped bacteria that play important roles in the environment and in human health.