NEET Biology Blue – Green Algae Are Called Cyanobacteria Notes

Cyanobacteria Blue-Green Algae For NEET Biology

Kail V. Non-Nncgcll distinguished blue preen algae from algae. Name k Aihku ten was given by Klilin nml Morris

Blue-Green Algae Main Features

1. Common forms include unicellular, colonial, filamentous, heterotrichous, Gram-variable, and photosynthetic.
2. The cell wall features an external layer that is gelatinous, viscous, and mucilaginous.
3. The cellular contents are partitioned into two regions: the outer chromatograms containing photosynthetic pigments and the inner colorless cytoplasm.
4. The cell wall consists of two layers, with the inner layer composed of peptidoglycan or mucopolysaccharides derived from amino sugars

Example: Glucosamine and amino acids

Example: Muramic acid and diaminopimelic acid

• Bacteria and cyanobacteria lack mitochondria, genuine vacuoles, and endoplasmic reticulum.
• Hormocyst. Thick-walled hormogonia or multicellular akinetes present in cyanobacteria.
• Sterols are nonexistent in both bacteria and cyanobacteria.
• No membrane-bound chloroplasts or photosynthetic lamellae, such as thylakoid arcs, are typically found in the peripheral cytoplasm.
• The authentic nucleus is lacking. Delicate DNA fibrils are either dispersed throughout the cell or concentrated in the central region. Its chromosome is analogous to a bacterial chromosome.
• Cyanobacteria lack distinct reproductive organs, sexual reproduction, and motile reproductive structures.
• Gas vacuoles are frequently found to modulate buoyancy in aquatic environments.
• Cyanobacteria inhabit nearly all aquatic habitats. The organisms inhabit tropical regions, plains, and are found in soil, freshwater, and marine environments.
• They constitute a component of plankton in lakes and oceans. Certain cyanobacteria inhabit the frigid waters of glaciers, while others thrive in hot springs with temperatures exceeding 85°C.
• Certain blue-green algae exist as symbionts with other organisms. For instance, they frequently constitute the algal components of lichens.

Blue Green Algae Notes For Neet

Shapes of Cyanobacteria

Cyanobacteria may be unicellular, colonial, or filamentous. Unicellular forms have single-celled body Examples Synecliococcus, Chroococcus, and Anacystis.

The colonial forms are of two types:

• Dendroid. They are the forms of cyanobacteria in which cells are held together by gelatinous connections example Chamae-siphon.
• Coccoid. They tire unicellular cyanobacteria embedded in a common matrix of mucilage without gelatinous connections, Example Microcystis. Filamentous forms are thread-like multicellular strands in which each filament or strand consists of a sheath of mucilage and one or more cellular strands called trichomes.
• Spirulina has a spirally coiled filament while a branched filament is found in Hapalosiphon.

Filaments that have single trichomes are divided into two types:

1. Homocystous. They have undifferentiated trichomes Example; Oscillatoria and Arthrospira.
2. Heterocystous. They have differentiated trichomes, for Example; Nostoc, and Rivularia.

In Schizothrix more than one trichomes are found in the same sheath of a filament. In Stigonema, a filament may have a few or a multiseriate trichome (in which numerous filaments are associated in a common sheath).

Classification based on morphology, motility, reproduction, and capacity of N2 fixation Cohen Bazire classified cyanobacteria into four groups:

1. Chroococcacean. Examples; Microcystis, Chroococcus, Gloeocapsa, etc.
2. Pseudocapsalean. Example Democarpa
3. Oscillatorian. Example; Oscillatoria.
4. Heterocystous. Examples; Nostoc, Aiiabacita, etc.
5. Among these groups, only Heterocystous has nitrogen-fixing capacity

Cyanobacteria Characteristics And Examples Neet

Economic Importance of Cyanobacteria

1. Useful activities.
   1. Nitrogen fixation is done by about 50 species of cyanobacteria. Based on nitrogen fixation there are two types:
   2. Free-living nitrogen-fixing cyanobacteria, for Example, Anahaeiui, Nostoc, Aulosira, Stylonenui, Stigonema, Oleotricltia, Calotlirix, TolypotlirLx, etc.
   3. They can fix approximately 15-48 kg of nitrogen per hectare per season. Aulosirafertilissima is the most active nitrogen fixer in Rice fields.
   4. Cslindnvpcrmum is an active nitrogen fixer of Sugarcane and Maize fields.
   5. Tolyptthrix is used as a nitrogen fixer in experimental fields. (hi Symbiotic nitrogen-fixing cyanobacteria: Anabaena and Nostoc species are common symbionts in lichens. Anihoceros, Azolla, and Cycas roots in which it can fix nitrogen.
   6. Azolla pinnata has Anabaena azollac in its fronds which is often inoculated to Rice fields for nitrogen fixation.
   7. They provide food for fish and other aquatic animals but Spirulina is regularly collected for human consumption in parts of Africa and India (from Samber Lake of Rajasthani. Nostoc in China, Anabaena in India.
   8. They provide suitable conditions for the growth of other organisms in a hostile environment.
   9. They are used as biofertilizers.
   10. Anabaena and Aulosira do not allow mosquito larvae to grow.
   11. They improve the physical texture of the soil.
2. Harmful activities
   1. Microcystis secretes hydroxylamine which kills aquatic life, birds, and cattle while Anabaena causes gastric trouble in domesticated animals by contaminating the drinking water of these animals.
   2. Microcystis aeruginosa (= Anacystis cyanea), Anabaena flosaquae and Aphanizoinenon flosaquae not only spoil the taste of drinking water but are also toxic to human beings.
   3. They cause depletion of supply to aquatic animals by the formation of blood by Microcystis, Anabaena, and Nostoc.
   4. Anacystis causes corrosion of metallic water pipes.
   5. The growth of algae is controlled by using algicides such as dichlorophen, phylon XI, exalgae, cushion, etc.

Mycoplasma

Cell walls are absent in the simplest and smallest free-living prokaryotes, which are frequently referred to as MLOs (Mycoplasma-like organisms) or PPLOs (Pleuropneumonia-like organisms).

• They are referred to as the “Jokers of the plant kingdom.”Mycoplasma gallispticum is the smallest prokaryote, measuring 0.3 to 0.5 m in size. The following were identified by Roux and Nocard in 1898.
• Nutritionally heterotrophic. Pleuropneumonia is produced in domestic animals, while Witch’s broom is produced in plants.
• Mycoplasma sensitivity. Mycoplasma is a gram-negative bacterium. Penicillin is ineffective against them; however, they are susceptible to other antibiotics, including streptomycin, chloramphenicol, and erythromycin.
• Their resistance to penicillin (and other antibiotics of the same class) may be attributed to the absence of a cell wall.
• This antibiotic disrupts the synthesis of peptidoglycan, a critical component of the bacterial cell wall.
• Reproduction. There is a lack of knowledge regarding mycoplasma reproduction.

However, four types of cellular bodies of Mycoplasma laidlawii have been found. These are:

1. Elementary bodies
2. Secondary bodies
3. Tertiary cell bodies and
4. Quaternary bodies

Elementary bodies reproduce by a process like budding. These grow in size and then again give rise to elementary bodies. In some cases, mycoplasma may reproduce by binary fission. Economic Importance Mycoplasma are always harmful and cause diseases in plants and animals.

Plant diseases. Many plant diseases caused by mycoplasma were earlier considered to be viral diseases before 1967. Since 1967 most of the plant diseases of the yellow group have been reported to be caused by mycoplasma.

These diseases are Little leaf of brinjal Citrus greening Sandal spike Grassy shoot of sugarcane Rice yellow dwarf Colton little leaf or cotton stenosis Sesamum phyllody and several others like Bunty top of papaya Aster yellows.

Neet Previous Year Questions On Cyanobacteria

Potato witch’s

• Pathologies in animals. Mycoplasma is responsible for diseases such as arthritis, various respiratory illnesses, and primary atypical pneumonia (PAP). Mycoplasma liowinis and M.fcrmcntans, among others, are believed to induce infertility in human males.
• In 1909, Howard Taylor Rickets identified novel microbes in the blood of individuals afflicted with Rocky Mountain spotted fever.
• This organism and others of its kind were designated as Rickettsiae, which are today classified as a category of bacteria. The designation Rickettsiae was conferred to pay tribute to the discoverer.

Rickettsiae differ from bacteria in having:

1. Smaller sizes with smaller genomes provide fewer enzymes. Requirement of an exogenous energy supplier for growth.
2. These organisms exist in alternate shapes and hence they are pleomorphic. They have no flagella, pili, capsules, or spores.
3. The cell wall is chemically similar to Gram (-) bacteria, The cytoplasm of Rickettsiae contains both DNA, RNA, and some enzymes.
4. Reproduction is by binary fission. Rickettsial infections usually respond to treatment with tetracyclines or chloramphenicol.