Bacteria - GCSE Biology Definition

Bacteria are microscopic, single-celled organisms that belong to the prokaryote kingdom, meaning they lack a true nucleus and membrane-bound organelles. They display a wide variety of shapes, such as rods, spheres, and spirals, and can be found in almost every environment on Earth, including soil, water, and the human body. Bacteria play diverse roles in ecosystems: some are essential for nutrient cycling through decomposition, while others help in processes like nitrogen fixation. In humans, they can be both beneficial, forming part of the normal flora, and harmful, causing diseases. Understanding bacteria is crucial for fields like medicine, agriculture, and biotechnology, where they can be harnessed for antibiotics production and genetic engineering.