Economic importance of Cyanobacteria | HSEB botany notes

Cyanobacteria are both useful as well as harmful to mankind and other living organism on the planet. The economic importance of cyanobacteria are as follows :

1. Cyanobacteria like Spriulina are cultivated in tanks as a protein rich food for fish and other animals.

2. Some blue green algae like Lyngbia can be used as antibiotics.

3. Species of cyanobacteria can grow on the walls and roofs of building during rainybseason causing discoloration, corrosion and leakage.

4. Nostoc sp benefits a number of plants with which it is associated by fixing nitrogen.

5. Even large colonies of Nostoc sp are edible.

Harmful effects :

6. Some cyanobacteria like Microcystis form water bloom on the surface of water and produce toxin ,and ultimatley pollute the water. The toxin is harmful to most aquatic animals and even to human beings.

Hseb Botany | Short notes on Archaebacteria

Archaebacteria is the most primitive and ancient bacteria. They are supposed to be oldest of the living fossils. They possess a unique cell wall that consists of polysaccharide and protein. They lack peptidoglycan (murein). The cell membrane contains branched-chain lipids, which enable them to withstand extremes of heat, high PH, absence of oxygen and high concentration.

Based upon ecological properties , the archaebacteria can be classified into three groups :

1. Thermoacidophiles (Temperature and acid loving) : They are aerobic forms of bacteria found in hot sulphur springs. They are high temperature and acid loving cyanobacteria. At 80 C, they oxidize sulphur to sulphuric acid in highly acidic medium. Under aerobic condition , these sulphur-dependent bacteria are called thermoacidophiles. These can reduce sulphur to H2S under anaerobic conditions.

2. Methanogens (Methane producers) : These are anaerobic archaebacteria which occur in marshy places and convert the formic acid or CO2 to methane. In biogas plants, they produce the methane gas, which is used as fuel.

3. Halophiles (Salt loving) : These are anaerobic bacteria which occur at salt rich soils. They prepare pigmented membrane in the presence of sunlight. This process is different from that of eukaryotic photosynthesis.

HSEB notes | Difference between gram +ve and gram -ve bacteria.

The difference between gram +ve (positive) and gram -ve (negative) bacteria are as follows : 

Gram +ve bacteria	Gram –ve bacteria
1. Their cell wall is 100-200 A thick       and homogenous.	1. Their cell wall is comparatively thin i.e 170-120 A and heterogenous.
2. They do not bear fimbriae or sex pilli.	2. They bear fimbriae or sex pilli
3. Peptidoglycan consists of about     70% of the cell wall.	3. Peptidoglycan consists of about 30% of the cell wall.
4. They retain deep blue or purple colour with crystal violet and subsequently with Potassium Iodide and alcohol.	4. They retain deep blue or purple colour with crystal violet and lost colour when treated with  Potassium Iodide and alcohol.
5. Mesosome is present.	5. Mesosome is absent.
6. They do not have resistant to Lysozome or antibiotics.	6. They show resistance with Lysozome or antibiotic due to the presence of lipid rich layer.