The cyanobacterium Anabaena grows well in liquid medium that contains nitrate as the sole nitrogen source. Suppose you transfer some of these filaments to the same medium except it lacks nitrate. Describe the morphological and physiological changes you would observe.
Anabaena lives as plankton. It is a genus that belongs to the filamentous cyanobacteria. They are well known for their nitrogen-fixing ability. They are seen in symbiotic association with some plants. These bacteria form a specialized structure known as heterocysts.
Explanation of Solution
Colonies of Anabaena grow as multi-cell chains. All the cells appear cylindrical otherwise barrel-shaped. The cells that are seen at the end of the chain are much longer when compared with others. When Anabaena that has been grown in the liquid medium with nitrate is transferred into the same medium lacking nitrate will show certain morphological as well as physiological changes. They are generation or formation of heterocysts that are able to fix nitrogen. Under nitrogen limiting conditions, the vegetative cells will be transformed into a heterocyst.
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Chapter 21 Solutions
Prescott's Microbiology
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