An outer membrane is seen in: all bacteria but not archaea all archaea but not bacteria all gram - A. bacteria all gram B. bacteria C. all prokaryotes but no eukaryotes

All gram (-) ve bacteria

Explanation:

The structure of bacteria demonstrates that the bacteria possess a cell wall which is composed of teichoic acid and peptidoglycan.

The cell wall thickness varies in the bacteria which is tested by the Gram staining technique. The bacteria with thick cell wall shows positive color or stain color so are called gram-positive bacteria and the bacteria with thin cell wall do not show the color and thus are called gram-negative bacteria.

However, the gram-negative bacteria also possess a layer of lipopolysaccharide and lipoproteins called LPS layer or outer layer surrounding the cell wall which is absent in the gram-positive and archaea bacteria.

Thus, All gram (-) ve bacteria is the correct answer.