Biological Classification – Eubacteria (True Bacteria)
Eubacteria are characterised by the presence of a rigid cell wall which is made up of Peptidoglycan, and motile bacteria possess a flagellum which is used for locomotion.
Eubacteria includes the following types:
Cyanobacteria (BGA) (blue-green algae) have chlorophyll-a similar to green plants which are found in chromatophores. Hence cyanobacteria are photosynthetic autotrophs.
· The cyanobacteria are unicellular and exist as colonial or filamentous, marine or terrestrial forms.
· The colonies of cyanobacteria are generally surrounded by a gelatinous sheath.
· They form algal blooms in polluted water bodies (Eutrophication).
B. Nitrogen fixing bacteria
These bacteria fix atmospheric nitrogen in specialized cells called heterocysts, example Anabaena & Nostoc. (Heterocyst provide anaerobic condition required for N2 fixation).
C. Chemosynthetic autotrophic bacteria
· They oxidize various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production.
· These bacteria play a major role in bio-geochemical cycles by recycling nutrients like nitrogen, phosphorous, iron and Sulphur.
D. Heterotrophic bacteria
· They are the mostly decomposers.
· Some help in making curd from milk, production of antibiotics, fixing nitrogen in legume roots, etc.
· Some are pathogens causing damage to human beings, crops, farm animals and pets.
· Tuberculosis, Typhoid, Cholera and tetanus are some of the diseases caused by different bacteria.