Difference Between Heterocyst And Akinete

Heterocysts and akinetes are special structures seen in some bacteria such as cyanobacteria. Both heterocysts and akinetes have specific functions and exhibit unique characteristics. 

Here are the difference between heterocyst and akinete.

Functional difference between heterocyst and akinete

• The main function of heterocysts is nitrogen fixation. Heterocysts are the site of nitrogen fixation in cyanobacteria. They provide anaerobic conditions inside the algal cell so the nitrogenase enzyme can convert atmospheric nitrogen into its most usable form for the bacteria.
• Akinetes are resting cells that help the cyanobacteria survive unfavorable conditions, like heat or drought. They are dormant structures that can withstand extreme conditions and later develop into organisms when conditions are favorable.

Structural difference between heterocyst and akinete

• Heterocysts are larger and elongated cells. They have thickened cell walls with certain structures called polar nodules where nitrogen fixation occurs. Heterocysts exist in chains or clusters with vegetative cells on either side.
• Akinetes are round or oval-shaped cells. Their thickened walls are multilayered. They contain reserve food materials that provide energy during their dormant stage. Akinetes exist as solitary cells.

Occurrence of heterocyst and akinete

Heterocysts are usually found in filamentous cyanobacteria where they form long chains or filaments of cells. Eg., Anabaena, Nostoc, and Calothrix.

Akinetes are seen in filamentous forms like Anabaena and Aphanizomenon, and in unicellular forms such as Gloeotrichia and Cylindrospermum.

Difference Between Heterocyst and Akinete in Environmental Conditions

• Heterocysts are formed when there is limited nitrogen availability or when the organism is supplied with an excess amount of fixed nitrogen sources.
• Akinetes are formed due to adverse environmental conditions like higher light intensity, nutrient depletion, extreme heat, or desiccation.

Difference Between Heterocyst and Akinete in their Metabolic Activity

• Heterocysts are metabolically active cells with unique enzymes and transport systems to help with nitrogen fixation.
• Akinetes are metabolically inactive cells while they are dormant. They reduce their metabolic activities gradually and stay inactive during dormancy. But can regain their activities once the conditions are favorable.

Conclusion

Even with such a wide range of differences, both heterocyst and akinete possess thick, multilayered envelopes made of outer polysaccharide and inner glycolipid layers. These layers help them adapt to stress conditions.