User:Nahim junior

Bacteria (singular-bacterium  )  are  very small, unicellular organism  whose  genetic material  is  not  enclosed  in  a special nuclear  membrane. For this  reason,  bacteria  are  called  procaryotes,  from Greek words  meaning  prenucleus.  Bacterial cells generally  appear  in  one  of several  shapes. Bacillus   (rodlike),  coccus  (spherical  or  ovoid)  and  spiral (corkscrew  or  curved)  are  the  most common  shapes, but some are  star-shaped  or   square.