Bacteria are prokaryotic microorganisms that are classified based on their shape, size, and structure. They are found in almost every environment on Earth, from deep-sea vents to arctic ice caps. Bacteria can be beneficial or harmful to humans, with some species causing infectious diseases and others contributing to overall health and well-being.

For instance, the human microbiome is made up of trillions of bacteria that live on and inside the human body, and they play an important role in digestion, immune function, and metabolic processes. Additionally, bacteria are used across various industries, from food production to environmental management, and their ability to rapidly evolve through genetic mutation and transfer has made them important models for studying genetic exchange and antibiotic resistance.