Bacteria
Most are helpful or harmless, but some may cause diseases. Bacteria obtain nutrients from their environments in order to live, in some cases the human body can be that environment. Bacteria can reproduce outside and inside the body as they cause infections. Pathogens are microorganisms that cause disease such as bacteria and viruses. Bacteria and viruses are the main pathogens. Bacteria are microscopic organisms. They come in many shapes and sizes, but even the largest are only 10 micrometers long (10 millionth of a meter). Bacteria are living cells and in some condition can multiply rapidly. Once inside the body, they release poisons or toxins that make us feel ill. Most diseases caused by bacteria include:
- food poisoning
- cholera
- typhoid
- whooping cough
- gonorrhoea - a sexually transmitted disease