Question

Heterocysts are present in _________.

Answer 1

Hint: In nitrogen fixation, Heterocysts are special types of cells. They express a gene nif which synthesizes enzyme nitrogenase that helps in fixing nitrogen when there is a shortage of fixed nitrogen.

Complete answer-
In filamentous organisms, heterocysts are present and with them they carry nitrogen-carrying machinery. Some organisms require nitrogen for biosynthesis and Heterocysts help in it by providing the enzymatic machinery and a safe micro anaerobic environment as nitrogenase is sensitive to oxygen. Cyanobacteria are gram negative bacteria known as Blue Green bacteria and also known as Blue Green algae. An outer peptidoglycan membrane they have. Filamentous cyanobacteria are multicellular organisms and are found in terrestrial habitats, like geothermal springs, hot deserts and polar regions. In conditions, continuous with the filamentous membrane the cyanobacteria outer membrane remains. Examples include : Anabaena and Nostoc. Hence, the Heterocysts are present in the – Cyanobacteria. Heterocysts have a thick cell wall. After every 9-15 cells in the filament they are present in Cyanobacteria. They have a distinct neck structure at their poles.

Note:
Multicellularity by the presence of the filaments that are composed of almost 100 cells are being shown by some of the cyanobacterial strains. Two cell types: Heterocysts that fix nitrogen develop during Nitrogen shortage and Vegetable cells that fix carbon dioxide. They are dependen