(1) The basic shapes of bacteria are spherical, rod-shaped and spiral-shaped.
(2) Bacteria have cell wall, cell membrane, cytoplasm and other structures. They are single-celled organisms. The main difference from animal and plant cells is that although bacteria have areas where DNA is concentrated, they do not have a nucleus. They are called prokaryotes. ．
(3) Some bacteria can form spores in adverse environments. They are dormant bodies of bacteria and have strong resistance to adverse environments.
(4) The rhizobia in the roots of leguminous plants can fix nitrogen in the air and provide nitrogen-containing nutrients for plant life.
(5) Saprophytic bacteria can decompose animal and plant remains, thus promoting the material cycle in nature. They are decomposers.
So the answer is: (1) Cocci, Spiral bacteria
(2) Cell, nucleus, DNA
(3) Spores
(4) Nodules
(5) Decomposition