Decomposition of dead organic remains is carried out by a group of saprophytic bacteria and fungi, which are called decomposers.

Decomposers break down the dead remains of plants and animals and waste products of animals and release nutrients into the soil.

BACTERIABACTERIA

FUNGIFUNGI

Nitrogen is an important element in the synthesis of plant and animal

proteins.

Atmospheric nitrogen cannot be absorbed directly by plants. Plants can only absorb nitrogen

in the form of ammonium, nitrite or nitrate ions.

Nitrates, in particular, are taken up by the roots of

plants and converted into plant proteins.

When the animals eat the plants, the organic nitrogen is transferred into the body of animals

and becomes animal proteins.

Nitrogen fixing bacteria such as Nostoc sp. , which lives freely in the soil, and Rhizobium sp. which lives in

the root nodules of leguminous plants, can convert atmospheric

nitrogen into ammonium compounds (NH3 and NH4 ) through a

process called nitrogen fixation.

NH3

Waste matter, and plants and animals which die, decompose and are

converted into ammonium compounds.

Ammonium compounds are converted into nitrites and

nitrates by nitrifying bacteria through a process called

nitrification.Ammonia is converted into

nitrites (NO2−) by Nitrosomona sp.

Nitrites are converted into nitrates (NO3-) by Nitrobacter

sp.

The cycle is balanced by a continuous return of nitrogen to the atmosphere by denitrifying bacteria. These bacteria break

down nitrates and release nitrogen back into the atmosphere.

Nitrobacter sp. Nitrobacter sp.

Microorganisms also play an important

role in the alimentary

canal of termites.

Population of mutualistic protozoans such as

Trichonympha sp. are present in the alimentary

canal of termites. They secrete cellulase which is

required by the termites to digest cellulose.

Termites feed mainly on wood which

contains cellulose. However, they are

unable to produce the enzyme cellulase to digest the cellulose.

Trichonympha sp.

Useful symbiotic bacteria are found in the human colon. The useful microorganisms

synthesise vitamins B12 and K which are often deficient in

the human diet.

ANTIBIOTICS

Poliomyelitis is a viral disease that can affect nerves and can lead to partial or full paralysis.

a. Sewage is the waste matter from households

and industries.

b. It is reach in organic matter, bacteria and other microorganisms.

c. Sewage from various households & industries is piped into large settling tanks in sewage treatment plants.

d. During the waste treatment process, millions of aerobic bacteria present in the sewage decompose organic matterin the presence of oxygen.

e. Most of the sludge that settles at the bottom of settling

tanks is pumped into the sedimentation tanks where fermentation takes place.

e. Most of the sludge that settles at the bottom of settling

tanks is pumped into the sedimentation tanks where fermentation takes place.

f. Here, anaerobic bacteria continue to decompose

the organic matter to methane & carbon dioxide, along with water & other

minerals.

f. Here, anaerobic bacteria continue to decompose

the organic matter to methane & carbon dioxide, along with water & other

minerals.

g. The methane gas is collected & used as fuel for

the engine pumps in the sewage plants

g. The methane gas is collected & used as fuel for

the engine pumps in the sewage plants

h. The digested sludge is rich in

nitrates & phosphates and

when it is dried it can be used as

fertilizers by farmers.

h. The digested sludge is rich in

nitrates & phosphates and

when it is dried it can be used as

fertilizers by farmers.

SLUDGE

The commercial use of microorganisms in food processing is based on the process of fermentation.

Fermentation is a metabolic process whereby electrons released from nutrients are ultimately transferred to molecules obtained from thebreakdown of those same nutrients

Fermentation is a metabolic process whereby electrons released from nutrients are ultimately transferred to molecules obtained from thebreakdown of those same nutrients

YEAST

a) Beer is brewed from barley grains.b) In commercial beer-making, two commonly used yeast species are S. cerevisiae and S. carlsbergensis (brewer yeast).

a) Beer is brewed from barley grains.b) In commercial beer-making, two commonly used yeast species are S. cerevisiae and S. carlsbergensis (brewer yeast).

a) Wine is made by the fermentation of grape juices.b) During fermentation, ethanol & carbon dioxide are released.

a) Wine is made by the fermentation of grape juices.b) During fermentation, ethanol & carbon dioxide are released.

Soy sauce is made from fermented soya beans by the action of fungi.

Soy sauce is made from fermented soya beans by the action of fungi.

S tS tL BL B

a) Yogurt is made from the fermentation of milk using bacteria, especially Lactobacillus bulgarius and Streptococcus thermophillus.b) These bacteria convert sugar into lactic acid which coagulates casein (milk protein).c) This creates the thick creamy yogurt

a) Yogurt is made from the fermentation of milk using bacteria, especially Lactobacillus bulgarius and Streptococcus thermophillus.b) These bacteria convert sugar into lactic acid which coagulates casein (milk protein).c) This creates the thick creamy yogurt

a) Cheese is made by mixing bacteria (etc, streptococcus sp.) with the enzyme rennin.b) The bacteria ferment milk sugar to lactic acid.c) The solid part of the milk (the curt) is separated from the liquid portion (the whey).d) The curds are pressed and moulded and then left to mature or ripen.

a) Cheese is made by mixing bacteria (etc, streptococcus sp.) with the enzyme rennin.b) The bacteria ferment milk sugar to lactic acid.c) The solid part of the milk (the curt) is separated from the liquid portion (the whey).d) The curds are pressed and moulded and then left to mature or ripen.

Rennin Strept

o-coccus

sp

a) BIOGASa) BIOGAS

Gasohol or biofuel is a combination of 10% ethanol and 90% petrol.

Sugar cane and maize are the main sources of gasohol. The cane or maize is crushed and sucrose is extracted to form a sweet syrup.

This syrup contains glucose and fructose which when left to ferment by adding yeast,will produce ethanol.The ethanol is distilled before it is used.

Gasohol is used widely as fuel or as an alternative to petrol in some countries.