What is the nature of cell walls in diatoms?

The cell walls in diatoms exhibit a highly unique and intricate structure. They are composed of two thin overlapping shells—referred to as the epitheca (upper layer) and hypotheca (lower layer)—which fit together in a manner similar to the two halves of a soapbox. This overlapping design not only provides structural integrity but also allows the diatom's shell to be both protective and lightweight.

The defining feature of diatom cell walls is their composition. These walls are embedded with silica, a material that renders them exceptionally rigid and virtually indestructible. Unlike most organic cell walls, the siliceous frustules of diatoms do not decompose after the organism dies. Instead, they accumulate at the bottom of water bodies, forming vast deposits known as diatomaceous earth or diatomite. These deposits are gritty in texture and have significant applications in industries such as filtration, insulation, and even drug delivery systems.

The silica-based cell walls of diatoms make them chemically inert, durable, and highly resistant to decay. This unique feature also allows diatoms to act as reliable indicators of clean water in environmental studies. Thus, the silica-embedded, overlapping nature of their cell walls is not only a hallmark of their biology but also the reason for their ecological and industrial significance.