Bacteria are unicellular microorganisms, among the earliest life forms on Earth, existing in diverse environments worldwide. They vary in types, inhabiting air, water, soil, plants, animals, and humans. While many strains are beneficial, aiding digestion and vitamin synthesis in the human gut, others cause infections, leading to bacterial diseases. Certain bacteria, like Salmonella and Pneumonia, pose significant risks to human health. Their ubiquity and diverse roles highlight their importance in ecosystems and human well-being.