What is the biology of a heterocyst?

Heterocyst biology has been relatively well studied at the biochemical and molecular levels. Heterocysts are the only cells that express nif (nitrogen fixation) genes and synthesize nitrogenase in heterocyst-forming cyanobacteria.

What is a heterocyst 3G?

Heterocysts (Figures 3 (c), 3 (g), and 3 (i)) are morphologically distinct cells that develop in response to a lack of combined nitrogen sources in the environment. The ability to develop heterocysts occurs without exception within a monophyletic group of filamentous cyanobacteria (heterocystous; subsections IV and V).

What is the role of heterocysts in aerobic fixation?

Heterocysts are highly specialized in the fixation of dinitrogen under aerobic conditions. They represent a successful solution to the nontrivial problem of avoiding nitrogenase inactivation by free oxygen in oxygen-evolving organisms. Heterocyst biology has been relatively well studied at the biochemical and molecular levels.

How long does it take for heterocysts to differentiate?

When there is not enough fixed nitrogen to go around, one of the vegetative cells becomes a heterocyst. Heterocyst differentiation takes approximately 24 hours. But they are dead end cells: unlike their vegetative counterparts they can no longer multiply. However, the vegetative cells surrounding them continue to do so.

Why are heterocysts dependent on vegetative cells for carbon fixation?

Because they lack photosystem II and carbon fixation, heterocysts are dependent on vegetative cells for a source of reductant and carbon, which is probably partially supplied as sucrose. HETEROCYST IN ANABAENA

What is the symbiotic relationship between heterocyst and vegetative cells?

Heterocyst and vegetative cells are symbiotically associated with each other where heterocyst provides with fixed nitrogen to the vegetative cells and vegetative cells act as the source of carbon and reductant for proper functioning of heterocyst.

How is carbohydrate transported into the heterocysts?

The heterocysts also lack Rubisco and the Calvin cycle enzymes so that CO2 fixation is limited to the vegetative cells. Thus carbohydrate has to be transported into the heterocysts, probably in the form of maltose.