Nostocales

Nostocales

Anabaena flos-aquae, a member of the order Nostocales

Nostocales is an order of filamentous cyanobacteria within the class Cyanophyceae. These organisms are known for their ability to perform photosynthesis and fix atmospheric nitrogen, making them important contributors to the nitrogen cycle in aquatic ecosystems.

Characteristics

Nostocales are characterized by their filamentous structure, which consists of chains of cells called trichomes. These trichomes can be straight, coiled, or irregularly shaped. A distinctive feature of many Nostocales is the presence of specialized cells called heterocysts, which are sites of nitrogen fixation. Heterocysts have thickened cell walls to protect the nitrogenase enzyme from oxygen, which can inhibit the nitrogen fixation process.

Ecology

Nostocales are found in a variety of aquatic environments, including freshwater lakes, ponds, and slow-moving rivers. They can also be found in terrestrial habitats, such as moist soils and rocks. These cyanobacteria play a crucial role in the ecosystem by contributing to primary production and providing a source of fixed nitrogen for other organisms.

Genera

The order Nostocales includes several well-known genera, such as:

• Anabaena - Known for forming symbiotic relationships with certain plants and producing toxins that can affect aquatic life and human health.
• Nostoc - Often found in terrestrial environments, forming gelatinous colonies that can survive desiccation.
• Aphanizomenon - Known for forming blooms in nutrient-rich waters, which can lead to eutrophication.

Importance

Nostocales are important in both natural and artificial ecosystems. In agriculture, some species are used as biofertilizers due to their ability to fix nitrogen. However, certain species can also produce harmful algal blooms, releasing toxins that can be detrimental to aquatic life and human health.

Related pages

• Cyanobacteria
• Photosynthesis
• Nitrogen fixation
• Heterocyst