Hormogonium

Hormogonium

Hormogonia of Nostoc at 40x magnification

A hormogonium is a specialized structure found in certain filamentous cyanobacteria, such as those in the genus Nostoc. Hormogonia are short filaments of cells that are capable of gliding motility and are involved in the dispersal and colonization of new environments.

Structure

Hormogonia are composed of a series of cells that are smaller and more rounded than the typical vegetative cells of the cyanobacterium. These cells are often separated by heterocysts or akinetes, which are specialized cells that serve different functions. The formation of hormogonia is typically induced by environmental factors such as light, nutrient availability, or the presence of a suitable substrate for colonization.

Function

The primary function of hormogonia is to facilitate the dispersal of the cyanobacterium. They are capable of gliding motility, which allows them to move across surfaces and find new locations to colonize. This motility is thought to be driven by the secretion of polysaccharide slime and the use of type IV pili.

Hormogonia also play a role in the symbiotic relationships that some cyanobacteria form with plants, such as the association between Nostoc and certain species of liverworts, hornworts, and cycads. In these symbioses, hormogonia are often the form of the cyanobacterium that initially infects the host plant.

Life Cycle

The life cycle of cyanobacteria that produce hormogonia involves several stages. Under favorable conditions, the vegetative cells of the cyanobacterium will differentiate into hormogonia. These hormogonia can then move to new locations, where they will eventually settle and differentiate back into vegetative cells, forming new filaments. This cycle allows the cyanobacterium to spread and colonize new environments efficiently.

Related Pages

• Cyanobacteria
• Nostoc
• Heterocyst
• Akinete
• Symbiosis