Cyanobacteria

Definition

Cyanobacteria are a group of photosynthetic bacteria that can produce oxygen as a byproduct of photosynthesis, similar to plants. They play a crucial role in nitrogen fixation, where atmospheric nitrogen is converted into ammonia, making it available for use by living organisms. This ability to fix nitrogen is vital for ecosystems, especially in environments where nitrogen is limited, and it supports the growth of various plants and organisms.

5 Must Know Facts For Your Next Test

1. Cyanobacteria are often referred to as blue-green algae, although they are prokaryotic bacteria and not true algae.
2. They are found in a wide range of habitats, including freshwater, marine environments, and even extreme conditions like deserts and hot springs.
3. Cyanobacteria contribute significantly to global carbon and nitrogen cycles due to their ability to fix atmospheric nitrogen and their role as primary producers.
4. Some cyanobacteria can form harmful algal blooms that produce toxins, impacting aquatic ecosystems and human health.
5. Cyanobacteria are believed to be one of the earliest forms of life on Earth, contributing to the oxygenation of the atmosphere over 2.4 billion years ago during the Great Oxidation Event.

Review Questions

• How do cyanobacteria contribute to nitrogen fixation and why is this process important for ecosystems?
  • Cyanobacteria contribute to nitrogen fixation by converting atmospheric nitrogen into ammonia through a specialized enzyme called nitrogenase. This process is essential for ecosystems because it provides bioavailable nitrogen, which is crucial for plant growth. In environments where nitrogen is scarce, cyanobacteria serve as a vital source of nitrogen, supporting the growth of various organisms in the food web.
• Discuss the environmental conditions that favor the growth of cyanobacteria and how these conditions relate to their role in ecosystems.
  • Cyanobacteria thrive in warm, nutrient-rich waters, particularly in environments with ample sunlight and limited competition from other organisms. These conditions often lead to rapid growth and can result in algal blooms. While these blooms can enhance productivity in aquatic systems, excessive growth can deplete oxygen levels and produce toxins that harm other aquatic life. Understanding these dynamics helps manage water quality and ecosystem health.
• Evaluate the ecological impacts of harmful algal blooms caused by cyanobacteria on aquatic systems and human activities.
  • Harmful algal blooms caused by cyanobacteria can lead to significant ecological disruptions in aquatic systems, including oxygen depletion and the release of toxins that affect fish populations and other wildlife. These blooms can create dead zones where aquatic life cannot survive, damaging fisheries and ecosystems. Furthermore, such blooms pose risks to human activities, particularly recreation and drinking water supply, prompting monitoring and management strategies to mitigate their effects on public health and the environment.

Related terms

Nitrogen Fixation: The process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds in soil and water, allowing it to be used by living organisms.

Chlorophyll: A green pigment found in cyanobacteria and plants that is essential for photosynthesis, allowing them to absorb light energy and convert it into chemical energy.

Heterocysts: Specialized cells found in some filamentous cyanobacteria that provide a microanaerobic environment for nitrogen fixation by separating the nitrogenase enzyme from the oxygen produced during photosynthesis.