Difference Between Nostoc and Anabaena

Key Difference – Nostoc vs Anabaena
 

Cyanobacteria or blue-green algae are important organisms in ecosystems. They are capable of photosynthesizing and producing their own foods. As a byproduct of photosynthesis, oxygen gas releases to the atmosphere. It is believed, cyanobacteria are the first organisms that contributed to creating an oxygenic atmosphere at the beginning of the life on Earth. There are different genera of cyanobacteria. Among them, Nostoc and Anabaena are two genera. Nostoc is a type of cyanobacteria that composes  gelatinous colonies formed from filamentous cells. Anabaena is another type of filamentous, bead-like cyanobacterium that exists as planktons. The key difference between nostoc and Anabaena is that vegetative cells of Nostoc are covered with mucilaginous sheath while cells of the Anabaena are not covered with a mucilaginous sheath.

CONTENTS

1. Overview and Key Difference
2. What is Nostoc
3. What is Anabaena
4. Similarities Between Nostoc and Anabaena
5. Side by Side Comparison – Nostoc vs Anabaena in Tabular Form
6. Summary

What is Nostoc?

Nostoc is a blue-green alga or cyanobacterium. Nostoc cells are  arranged in beadlike chains, and it forms colonies that are covered with mucilaginous sheaths.  Nostoc is frequently found in still water habitats. And also nostoc can be found in the soil. Nostoc has two pigments that give the characteristic blue-green colour to Nostoc. They are blue phycocyanin and red phycoerythrin. Other than these two pigments, Nostoc has chlorophyll a pigment for capturing sunlight and photosynthesizing. Nostoc has the capability of fixing atmospheric nitrogen. This ability is facilitated by the structures called heterocysts possessed by Nostoc.

Figure 01: Nostoc

The reproduction of nostoc usually occurs through fragmentation. Nostoc has special dormant structures or cells to withstand the harsh environmental conditions. They are known as akinetes. Akinetes are thick-walled cells that have the ability to resist from desiccation. Nostoc serves as a good supplementary food source in Asia.

What is Anabaena?

Anabaena is a cyanobacterium that is composed of beadlike or barrellike cells formed into colonies. It is a filamentous cyanobacterium that normally exists as plankton. It has uniform trichomes. Anabaena cells are not covered with a mucilaginous sheath. The vegetative cells or trichomes of Anabaena are arranged in chains, and they are not branched.

 It is found in symbiotic relationships with certain plants. One common water fern is Azolla. The association of Anabaena with plants provides plants nitrogen while plants supply carbon for Anabaena. Therefore, most of the rice farmers use Azolla fern which has Anabaena as an organic fertilizer to supply nitrogen into rice plants. Anabaena possesses the ability to fix atmospheric nitrogen. Nitrogen fixation is carried out by the specialized cells called heterocysts of Anabaena. Heterocysts develop from vegetative cells for the above purpose. Anabaena is a photoautotrophic cyanobacterium. It performs oxygenic photosynthesis and produces its own foods. During the photosynthesis, it releases oxygen into the atmosphere.

Figure 02: Anabaena

Anabaena can be found in fresh water, and it is considered as a contaminant of drinking water since it gives fishy odour and taste. Anabaena is popular as a producer of neurotoxins, which is a harmful product for wildlife. Similar to Nostoc, Anabaena is also reproduce by fragmentation. And also it possesses akinetes to withstand harsh environmental conditions.

What are the Similarities Between Nostoc and Anabaena?

• Nostoc and Anabaena are prokaryotic organisms. Hence they don’t have a true nucleus.
• Nostoc and Anabaena are two bacterial species.
• Both Nostoc and Anabaena are filamentous, and they possess unbranched trichomes.
• Both Nostoc and Anabaena are cyanobacteria or blue, green algae.
• Both Nostoc and Anabaena can fix atmospheric nitrogen.
• Both Nostoc and Anabaena can do photosynthesis.
• Both Nostoc and Anabaena have heterocysts.
• Both Nostoc and Anabaena are found in moist environments.
• Nostoc and Anabaena belong to the same order and family.
• Both Nostoc and Anabaena use fragmentation as a method of reproduction.
• Both Nostoc and Anabaena possess akinetes for the tolerance of harsh environmental conditions.

What is the Difference Between Nostoc and Anabaena?

Summary – Nostoc vs Anabaena 

Anabaena and Nostoc are two cyanobacteria that can photosynthesize and fix nitrogen. Both are able to make symbiotic relationships with certain plants. Both possess heterocysts and akinetes. Both forms are filamentous and have vegetative cells that are beadlike. Both cyanobacteria cells are arranged in chains. Both possess chlorophyll a and phycocyanins. Both nostoc and Anabaena reproduce by fragmentation. The difference between nostoc and Anabaena is that Nostoc has a mucilaginous sheath covering its vegetative cells while it is absence is Anabaena.

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Reference:

1.The Editors of Encyclopædia Britannica. “Nostoc.” Encyclopædia Britannica, Encyclopædia Britannica, inc., 2 Nov. 2016. Available here  
2.“Anabaena.” Anabaena – microbewiki, Available here 

Image Courtesy:

1.’Nostoc commune’By YAMAMAYA – Own work, (CC BY-SA 3.0) via Commons Wikimedia 
2.’Anabaena sperica2′ (CC BY-SA 3.0) via Commons Wikimedia

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