What is the Difference Between Nostoc and Anabaena

The main difference between Nostoc and Anabaena is that Nostoc is a genus of cyanobacteria, and forms colonies composed of filaments of moniliform cells in a gelatinous sheath, whereas Anabaena is a genus of filamentous cyanobacteria, and exists as plankton. Nostoc and Anabaena are two genera of nitrogen-fixing cyanobacteria. Nostoc is free-living in terrestrial and aquatic habitats while Anabaena forms symbiotic relationships with some plants including mosquito fern. 

Key Areas Covered 

1. What is Nostoc
     – Definition, Structure, Importance
2. What is Anabaena
     – Definition, Structure, Importance
3. What are the Similarities Between Nostoc and Anabaena
     – Outline of Common Features
4. What is the Difference Between Nostoc and Anabaena
     – Comparison of Key Differences

Key Terms 

Anabaena, Cyanobacteria, Nitrogen-Fixing, Nostoc

What is Nostoc 

Nostoc is a genus of cyanobacteria characterized by the formation of cylindrical, spherical or ovoid colonies. The filaments of these colonies are embedded in a gelatinous substance. Further, Nostoc lives in various environments, including the soil, moist rocks, freshwater, and marine habitats. And, it forms symbiotic relationships within plant tissues of hornworts, Gunnera, etc. Besides, terminally-differentiated heterocysts are the type of cells in Nostoc, involving in the nitrogen-fixation. Also, Nostoc contains photosynthetic pigments in the cytoplasm to undergo photosynthesis.

Figure 1: Nostoc

Due to the containment of proteins and vitamin C, Nostoc is consumed as a foodstuff in Asia. Moreover, the common names for Nostoc are star jelly, troll’s butter, witch’s butter, and witch’s jelly.  

What is Anabaena 

Anabaena is a filamentous, nitrogen-fixing cyanobacterium characterized by the formation of intercalary heterocysts and isolated, amorphous filaments. It produces akinetes, which are enveloped, thick-walled, non-motile, dormant cells. Also, Anabaena forms symbiotic relationships with several plants, including mosquito fern. Moreover, in these plants, Anabaena produces neurotoxins harmful to local wildlife. Besides, it also protects plants from grazing pressure. 

Figure 2: Anabaena

Moreover, same as Nostoc, Anabaena is a photosynthetic organism, and it fixes nitrogen as well. Here, vegetative cells differentiate into heterocysts under nitrogen-limiting conditions. Heterocysts also occur at semi-regular intervals along the filaments. Generally, heterocysts terminally-differentiate for nitrogen fixation. 

Similarities Between Nostoc and Anabaena 

• Nostoc and Anabaena are two genera of Nitrogen-fixing cyanobacteria. 
• Both cyanobacteria are prokaryotes. 
• Moreover, they belong to the family Nostocaceae under the order Nostocales. 
• They are photosynthetic.  
• Both are free-living in aquatic and terrestrial environments.  
• They form akinetes, heterocysts, and unbranched trichomes. 
• They also do not produce spores. 
• Furthermore, these cyanobacteria undergo vegetative reproduction by fragmentation. 

Difference Between Nostoc and Anabaena 

Definition 

Nostoc refers to the cyanobacteria composed of beaded filaments, which aggregate to form a gelatinous mass, growing in water and damp places and able to fix nitrogen from the atmosphere, while Anabaena refers to a genus of freshwater cyanobacteria, having cells in beadlike filaments and often contaminating reservoirs, giving a fishy odor and taste to the drinking water.  

Habitat 

Furthermore, Nostoc is free-living in aquatic or damp habitats while Anabaena forms a symbiotic relationship with mosquito fern, legumes, rice plant, etc. 

Depth Range 

While Nostoc exists on the water surface, Anabaena exists within 1m of the depth of the water body. 

Temperature 

Nostoc can adapt to extreme temperatures while Anabaena exists in a wide temperature range up to 74 degrees of Celcius. 

Morphology 

Another difference between Nostoc and Anabaena is their morphology. Nostoc forms a gelatinous colony, appearing cylindrical, spherical or ovoid while Anabaena forms filaments, which are coiled or straight. 

Size 

The size of the colonies of Nostoc is around 20 cm while the cell size of Anabaena is 4-50 micrometer. 

Reproduction 

Moreover, Nostoc reproduces either by simple fission or fragmentation while Anabaena reproduces either by trichome fragmentation at heterocysts or by akinetes. 

Conclusion 

Basically, Nostoc is a genus of cyanobacteria that form basically cylindrical colonies. On the other hand, Anabaena is another genus of cyanobacteria, which forms coiled or straight filaments. Nostoc is mainly free-living in aquatic habitats while Anabaena is symbiotic in several plants. However, both Nostoc and Anabaena are nitrogen-fixing cyanobacteria. Thus, the main difference between Nostoc and Anabaena is their habitat and morphology. 

References:

1. Benitez, Ezel Anne. “Anabaena and Nostoc.” LinkedIn SlideShare, 14 Aug. 2014, Available Here.

Image Courtesy:

1. “CyanobacteriaColl1” By Christian Fischer (CC BY-SA 3.0) via Commons Wikimedia   
2. “Anabaenaflosaquae EPA” By Environmental Protection Agency (Public Domain) via Commons Wikimedia