1. Cell Wall: This rigid outer layer provides shape and protection to the cell. It's made of peptidoglycan, a unique molecule found only in bacteria. The structure of the cell wall is used to classify bacteria into two main groups: Gram-positive and Gram-negative.

2. Ribosomes: These are essential for protein synthesis. Bacteria have 70S ribosomes, which are smaller than the 80S ribosomes found in eukaryotic cells. This difference is important for the development of antibiotics that target bacterial ribosomes without harming human cells.

There are many other important structures in bacteria, but these two are essential for their survival and function.