HAFIZUDDIN BIN RAHIMAN MOHD HISHAMUDDIN BIN SAHDAN

AZOBACTER AND

RHIZOBIUM

IntroductionBoth are soil bacteriaAzobacter is a free-living bacteriaRhizobium basically in soilMost 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.

Azobacter

Soil bacteriaThe 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).

As nitrogen fixerThese 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".

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

Benefits as biofertilizerThese 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 biofertilizerIts capability in maintaining the pH, safe to

use and compatible as chemical fertilizer

Rhizobium Rhizobium is primarily a gram negative,

motile, non-sporulating rod that requires a plant host.

Species under this genus:1. R. phaseoli2. R. leguminosarum3. R. trifolii

Other genus are cowpeas Rhizobium and Bradyrhizobium

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.

Rhizobium