Azotobacter is a genus of free-living, motile bacteria known for forming cysts and their ability to fix atmospheric nitrogen into ammonia. They are predominantly found in neutral to alkaline soils and have significant metabolic capabilities, making them valuable for agricultural nitrogen fixation. Their unique nitrogenase enzymes and high metabolic rate contribute to their role in nutrient competition and growth promotion in various environments.

1. Azotobacter : Beneficial Microbes
Presented by:
Khushbu’s Microbiology

2. Genus of usually motile
 Oval or spherical bacteria
 Thick-walled cysts
 May produce large quantities of
capsular slime.
Azotobacter species cells:
stained with Heidenhain's
iron hematoxylin, ×1000
Azotobacter

3. Description
 Genus of free-living diastrophic bacteria
whose resting stage is a cyst.
 It is primarily found in neutral to alkaline soils,
 Aquatic environments, and on some plants.
 IMAGE : Azotobacter cyst.

4. Significance
 It has several metabolic capabilities : including atmospheric
nitrogen fixation by conversion to ammonia.
 Their unique system of three distinct nitrogenase enzymes
makes these bacteria of particular interest to scientists, who
may work toward a better understanding of nitrogen fixation
and its role in agriculture.
 Azotobacter spp: the highest metabolic rate of any organisms.

5. Advantages of Azotobacter:
 Heaviest breathing organism and requires a
large amount of organic carbon for its
growth.
 Competitor for nutrients in soil
 Growth promoting substances
 Fungistatic substances.

6. Nitrogen fixation
• Azotobacter species are free-living, nitrogen-
fixing bacteria; in contrast to Rhizobium species,
• They normally fix molecular nitrogen from the
atmosphere without symbiotic relations with
plants, some Azotobacter species are associated
with plants.
• Nitrogen fixation is inhibited in the presence of
available nitrogen sources, such as ammonium
ions and nitrates.

7. Nitrogen fixation
Azotobacter species have a full range of
enzymes needed to perform the nitrogen
fixation:
 ferredoxin,
 hydrogenase,
 important enzyme nitrogenase.
The process of nitrogen fixation requires an
influx of energy in the form of adenosine
triphosphate

8. NITROGEN CYCLE

9. • THANKS