B. Bacillus
Bacteria are single celled microorganisms. They have a simple cell structure than other organisms because they have no nucleus and no cell membrane. Their control center containing the genetic information si contained in a single loop of DNA. They are classified into five groups according to their shape; cocci are spherical, bacilli are rod shaped, spirilla are spiral, vibrios are comma and spirochaetes are corkscrew. They can exist as singe cells in pairs, chains or clusters. Rod shaped bacteria are called bacilli.