1. AZOBACTER
AND
RHIZOBIUM
HAFIZUDDIN BIN RAHIMAN
MOHD HISHAMUDDIN BIN SAHDAN
2. Introduction
Both are soil bacteria
Azobacter is a free-living bacteria
Rhizobium basically in soil
Most bacteria in soil are about one micron in length or
diameter (there are a thousand microns in a millimetre).
Some are slightly larger than this, up to several microns,
and in rare cases even larger. Their size varies with their
environment.
Bacteria in environments that have high levels of nutrients
may be larger than those in nutrient poor conditions.
4. Soil bacteria
The majority of bacteria in soil usually occur as single
cells. Bacteria sometimes join together in chains or
clusters. They mainly have one of two shapes - spheres
(called cocci) and rods (called bacilli). Other bacteria
have more varied shapes including spirals and long
thin hyphae (although these are less common).
5. As nitrogen fixer
These bacteria take nitrogen from the air (which
plants cannot use) and convert it into a form of
nitrogen called ammonium (NH4+), which plants can
use.
The nitrogenase enzyme controls the process, called
nitrogen fixation, and these bacteria are often called
"nitrogen fixers".
6. It converts atmospheric nitrogen into
ammonium, but in the condition of :
An easily degradable carbon source is
available
Any nitrogen compounds such as
ammonium or nitrate, are not already in
present in substantial concentrations
Soil pH levels are between 6 and 9
High levels of phosphorus are present
Very low levels of oxygen are present
7. Benefits as biofertilizer
These are primarily used to enhance the growth of
several species of plants and crops.
A correct proportion of bacterial growth could ensure
a high quality of biofertilizer
Its capability in maintaining the pH, safe to use and
compatible as chemical fertilizer
8. Rhizobium
Rhizobium is primarily a gram negative, motile, non-
sporulating rod that requires a plant host.
Species under this genus:
1. R. phaseoli
2. R. leguminosarum
3. R. trifolii
Other genus are cowpeas Rhizobium and
Bradyrhizobium
9. In agricultural
Rhizobia belong to a specific group of bacteria that
form a mutually beneficial association, or symbiosis,
with legume plants.
Rhizobia are found in soils of many natural
ecosystems. They may also be present in agricultural
areas where they are associated with both crop
legumes (like soybean) and pasture legumes (like
clover).
Usually, the rhizobia in agricultural areas have been
introduced at sowing by applying an inoculum to the
exterior of the seeds as liquid formations or pellets.
