this document contains deep knowledge about a microorganism and its functions. the structure of the microorganism is also explained with suitable images.
MICROORGANISMS
Microorganisms in nature
Microorganisms play an intrinsic role in almost every natural cycle. Found in
most environments, from aquatic to land, air, inside the human body, and even
in extreme environments such as hydrothermal vents and volcanoes,
microorganisms are an essential part of the web of life.
Microbes help to break down organic matter from plants, animals, and other
microbes. They are involved with the nitrogen and carbon cycles.
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen from the atmosphere is
converted into nitrate, nitrite and ammonium.
Nitrogen is essential to plants as it is an important component of amino
acids and chlorophyll.
There are four key stages of the nitrogen cycle:
• Nitrogen fixation
• Ammonification
• Nitrification
• Denitrification
Nitrogen fixation
During nitrogen fixation, atmospheric nitrogen is converted into nitrates and
nitrites. Plants cannot use atmospheric nitrogen until it has been fixed. The
majority of nitrogen fixation is performed by bacteria, either free-living
(e.g. Azotobacter) or symbiotic (e.g. Rhizobium). These bacteria live in the root
nodules of legumes, including beans and peas.
, Ammonification
Ammonia can be also be produced directly by the decomposition of plants and
animals, or via the production of waste by animals. This decomposition forms
organic nitrogen, which is then converted by bacteria (either aerobic or
anaerobic) and fungi into ammonia.
Nitrification
Nitrification is the process by which ammonium is converted into nitrite, and
then to nitrate. The first step is the conversion of ammonium to nitrite. This is
performed by different species of bacteria including Nitrosomonas. These
bacteria are widespread in soil, and use electrons from ammonia to generate
energy. Species such as Nitrobacter perform the second nitrification step,
converting nitrite in the soil into nitrate. Nitrobacter is an obligate aerobe,
meaning it needs oxygen to survive.
Denitrification
Denitrification completes the nitrogen cycle. Here, nitrate is converted back
into nitrogen gas. This stage of the nitrogen cycle is anaerobic, meaning it is
performed in the absence of oxygen. When soils become waterlogged, the
amount of oxygen available in the soil decreases. This allows denitrification to
occur, catalysed by facultative anaerobic bacteria.
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