Not all bacteria cause disease. Many bacteria live in or on our bodies and provide vital services. Bacterial cells have no nucleus or any membrane-bound organelles and so are prokaryote cells.
Chlamydia is the most common sexually transmitted infection in Britain. It is caused by bacterium called chlamydia trachomatis which is transmitted by direct contact during sexual intercourse.
If left untreated, it can cause infertility in adults and could also cause conjunctivitis in babies during the process of birth if the mother is infected.
It can also spread to the lungs of babies as they pass through the birth canal, causing pneumonia.
Its spread can be prevented by the use of condoms and it can be treated with antibiotics such as tetracycline or erythromycin.