Kingdom-monera-Bacteria-Mycoplasma-Conjugation | uksir-notes | Diversity-Living-World3
Diversity in Living World 3
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| Prokaryotes |
Kingdom - Monera
- Kingdom--Monera was introduced by Copeland in 1956.
- contain all the prokaryotic organisms
- including bacteria, archaebacteria, mycoplasma,
actinomycetes, cyanobacteria etc.
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| Prokaryotes |
Prokaryotes (Gr. Pro-primitive, karyos-nucleus)
- -Are primitive nucleus containing organisms.
- The word primitive nucleus here implies to a non organised
nucleus.
- usually seen in the
form of a double-stranded DNA coil.
General characteristics
1. Genetic material is
naked with circular DNA.
2. The cell lacks major membrane bound cell
organelles such as mitochondria, Endoplasmic Reticulum (ER), plastids, etc.
3. The cell wall if present
is a rigid structure that provides protection. It is made up of peptidoglycon.
4. ribosomes of 70 S type, with 50 S and 30 S
sub units are present.
5. mesosome replace
mitochondria.
Following types are discussewd below:
Bacteria
- Bacteria are cosmopolitan, i.e. found everywhere.
- Approximately, 4000 species described from all over the
world out of which about 850 species are found in India.
- discovered by A.v. Leeuwenhoek in 1683. ( Father of Bacteriology.)
- The term 'Bacteria'
was given by Ferdinand Cohn in 1872.
Size of bacteria - greatly varies, but most of them are 1-5 um in
diameter.
Shape of bacteria
bacteria can be of following types
1. Cocci/ Coccus- spherical or oval-shaped
bacteria, if don’t possess flagella
(atrichous).
They are subdivided into six groups
(i) Monococci- occur singly.
(ii) Diplococci-
occur in a pair of two.
(iii) Streptococci -occur in the form of chains.
(iv) Tetracocci- occur in a group of four.
(v) Sarcinae- occur incubical packets or in 3D
Form.
(vi) Staphylococci - occur in irregular bunches
of cells.
2. Bacilli (Sing. Bacillus) - These are rod-like
or cylindrical forms that are most commonly
subdivided into four main groups
(i) single bacillus, e.g. Rhodospirillum sodomense.
(ii) arranged in pairs -diplobacilli, e.g.Bacillus subtilis.
(iii) chain of rods - streptobacilli, e.g. Bacillus anthracis.
(iv) cells lined side by side - palisade-like,
e.g. Corynebacterium diphtheriae.
3. Spiral (Sing. spirillum)
- These bacteria are spiral-shaped and usually curved.
- mostly occur singly, e.g. Spirillum
rubrum.
4. Vibrio
- curved- like a comma.
- These forms possess mostly one flagellum, e.g. Vibrio cholera
Reproduction
- Mostly reproduce by a simple form of asexual reproduction and
very rarely by sexual reproduction.
takes place by following methods
(1) Vegetative reproduction
- Binary fission It is the most common means of bacterial multiplication.
- Cell replicates its DNA
- The cytoplasmic membrane
elongates separating DNA
- A transverse septum formation
takes place
- Completion of septum
- daughter cells separate
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| Fission-spore |
2.Asexual reproduction
- Sporulation
- Spore formation is very common.
- Most of these spores are non-motile in nature,
- e.g. conidia(e.g. Streptomyces), oidiospores (e.g.
Actinomyces), endospores, etc.
- Out of these endospores are
most common.
- These are highly resistant, single-celled structures.
- Formed during unfavorable condition.
- cytoplasm Contain DNA, RNA and proteins with reserve food.
- Central core is surrounded by a spore wall of 2 to 3 layers.
- In favorable environmental conditions, these spores germinate
to form vegetative cells.
-
3. Sexual reproduction (Genetic Recombination)
- In this mode, there is no formation of gametes and cell fusion.
- Only exchange of genetic material takes place in bacteria.
- Thus, the process is better known as genetic recombination.
- following methods of genetic recombination occurs:
(i) Transformation
- The bacterial transformation
was reported by Frederick Griffith 1920s in a series of
experiments.
- He used bacterium Diplococcus pneumoniae.
- Here free naked DNA (of a solution) is incorporated into a
recipient bacterial cell.
- This is responsible for the genetic change.
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| Transformation |
(ii) Transduction
- It was first reported
by Zinder and Lederberg in 1952.
-
In transduction a small piece of DNA is
transferred from one cell to another by a bacterial virus, i.e. bacteriophage.
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| Transduction |
(iii) Conjugation
- conjugation is the process that involves cell-to-cell
contact.
- Transfer of DNA directly from cell to cell through
conjugation tube.
- It was reported by Tatum and Lederberg in 1946.
- It occurs between a male or donor cell or F+ cell,
which
contains plasmid and a female, (F- )
or recipient cell, which do not contain any Plasmid.
- Plasmid transfer from male cell to female cell through the
conjugation tube.
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| Conjugation |
Economic importance of bacteria
Harmful bacterial activities
- (i)
Water pollution- Several bacterial forms cause water pollution,
by spoiling drinking water, e.g. Vibrio cholerae,
Salmonella typhi etc.
- (ii)
Reduction of soil fertility.
- (iii)
Food spoilage- The bacteria like Micrococcus, Salmonella, Staphylococcus, Clostridium, etc. spoil
the food stuffs.
- (iv)
can be used as Bioweapons - Pathogenic bacteria those causing anthrax, botulism, cholera, tuberculosis,
etc.
- (v)
Plant diseases and Animal diseases - causes several diseases
in plants and animals.
- E.g. - Xanthomonas malvacearum,
Xanthomonas campestris, Xanthomonas oryzae,
Pseudomonas solanacearum, Xanthomonas citri, Agrobacterium
tumefaciens
Useful bacterial
activities
(i) Antibiotic production-
- Antibiotics are the
drugs, which work against pathogens.
- About 2100 antibiotics have been reported.
Bacitracin, Polymixin-B, Terramycin, Eumycin
etc.
(ii) Soil fertility
- in agriculture Bacteria maintain soil fertility by nitrogen-fixation.
(iii) Industrial uses
- Used
in Milk industry, Leather Industry, Organic Acid Production, vitamin production
etc.
Mycoplasma (PPLO)
- These are the simplest and the smallest free-living prokaryotes.
- Mycoplasma were first isolated by E Nocard and ER Roux in
1898
- also called Pleuropneumonia Like Organisms (PPLO).
- Smallest mycoplasma is Mycoplasma
gallisepticum (about 0.1 um).
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| PPLO-Mycoplasma |
General characteristics
- 1. They are obligate parasites that can survive without oxygen.
- 2. cell wall is absent in them.
- 3. They cause pleuropneumonia, rheumatism, inflammation in
genitals, etc. in humans. In plants ,they cause clover draft, potato witch's
broom, maize stunt, etc.
Structure
- The plasma membrane is three-layered. It is made up of
lipoprotein.
- The genetic material is a single, double-stranded molecule of
DNA
- Cytoplasm contain – Granule- Ribosomes (70S), Enzymes
RNA, DNA (Double-stranded circular)
Reproduction
- They reproduce by budding, fragmentation and binary fission.
- They are generally non-motile, but some time gliding movement
seen.
Cyanobacteria
- Gram negative prokaryotes, which perform oxygenic photosynthesis.
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| BGA-Cyanobacteria |
General characteristics
1.mostly fresh water forms, but a few are marine as well.2. Photosynthetic pigments include chlorophyll-a, carotenoids, C-phycocyanin (blue coloured) and C-phycoerythrin (red coloured).
3. Food is stored in the form of cyanophycean starch.
Structure
1. Cyanobacteria can be unicellular, colonial or filamentous. (filament
consists of a sheath of mucilage).
2. They can fix atmospheric nitrogen with the help of a specialized
structure called heterocyst.
3. May occur in terminal, inter callary or lateral position
within the filament.
4. Heterocysts possess enzyme nitrogenase that perform
Nitrogen-fixation, e.g. Nostoc,
(intercalary)
Reproduction
1. They reproduce asexually by fission and fragmentation,
Sexual reproduction is totally absent.
2. Flagella are completely absent, Movement
occurs by gliding motion
Economic importance
1. Oscillatoria- acts as indicator of water pollution
2. Spirulina- protein rich animal food supplement,
3. increases soil fertility. Some time act as decomposer.
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