The bacteria are very small in size. Majorly these sizes are range from 0.5-5.0µm. The eukaryotic cell is 10 times more than the bacterial cell. Due to very less size the transmission of bacteria very rapid. These cause various types of diseases like malaria, typhoid etc. The smallest bacteria is Mycoplasma it’s size approximately 0.3µm. This bacteria size near to large virous.Thiomargarita namibiensis is largest bacteria ever discovered the size is range from 0.1 to 0.3mm in size.