Kingdom Monera
Characteristics:
- They are cosmopolitan in distribution (found in all types of habitat ).
- They are either unicellular or multicellular microscopic organisms.
- They are prokaryotes with incipient nucleus. They lack a true nucleus, that is nucleus without nuclear membrane, nucleoplasm, nucleolus and chromatin fibre.
- . Nuclear body consists of circular DNA, RNA and protein.
- The DNA molecule is naked that is it has no protein covering.
- They lack membrane bound cell organelles such as mitochondria, plastid, endoplasmic reticulum Golgi bodies etc.
- They possess a rigid cell wall.
- They have an autotrophic or heterotrophic mode of nutrition.
- Ribosome is of the 70s type.
- Photosynthetic pigments may or may not present.
- They are known as decomposers and mineralisers in the biosphere.
- The reserve food material is glycogen or fat or cyanophycean starch.
- They reproduce by vegetative and asexual methods. Absence of sexual reproduction.
Bacteria
Bacteria smallest, simplest, microscopic, prokaryotic organisms. It was first of
all discovered by Anton van Leeuwenhoek in 1675. He called them tiny
animalcules. But the present name bacteria was given by Ehrenberg (1828). The
branch of biology that deals with the study of bacteria is called bacteriology.
Father of bacteriology - Robert Koch
Founder of bacteriology - Louis Pasteur.
Characteristics of bacteria
- They are cosmopolitan in distribution and found in all types of habitat.
- They are the simplest, smallest, microscopic, prokaryotic organisms.
- They lack well organised nucleus having nuclear membrane, nucleoplasm, nucleolus and chromatin fibres.
- They bear only naked DNA as a nuclear body. so it is also known as incipient nucleus.
- The DNA is circular without histone protein.
- They don't bear membrane bound cytoplasmic organelles like mitochondria, golgi body, endoplasmic reticulum, plastids etc.
- Their cells are bonded by thick and rigid covering called the cell wall which is made up of acetyl glucosamine, acetyl muramic acid and Diamino pimelic acid.
- They bear small sized ribosomes called 70s ribosomes.
- They have autotrophic and heterotrophic modes of nutrition.
- Presence of gas vacuoles instead of sap vacuoles.
- The reserve food material is in the form of glycogen and lipids.
- They reproduce vegetative and asexual methods. Absence of sexual reproduction. Genetic recombination takes place by conjugation, transformation and transduction in some bacteria.
- They are known as decomposers and mineralisers in the biosphere.
Morphology of bacteria:
Average size of bacteria is 2um (1u = 1 / 1000mm). Smallest bacteria is cold
causing bacteria called Dialister pneumosintes (0.15 - 0.3 um). Largest bacteria
Beggiatoa mirabilis (16- 45 um in diameter and longest bacterium is Bacillus
butschlii (800u length).
Bacteria are found in different morphological forms. These are:
1. Coccus 2. Bacillus 3. Vibrio 4. Spirillum 5. Stalked 6. Mycelial 7.
Budding
- Coccus: They are rounded or oval in structure. They may be solitary or colonial in habitat. on the basis of their arrangement, they are of following types.
b. Diplococci: Coccus bacteria found in groups of two.
c. Tetracocci: Coccus bacteria found in groups of four.
d. Streptococci: large numbers of Cocci bacteria are attached with
each other forming a chain-like structure.
e. Staphylococci: large numbers of Cocci bacteria are arranged forming
a cluster like the grape.
f. Sarcina: large numbers of Cocci bacteria are arranged forming a 3-
dimensional structure.
- Bacillus: They are elongated or rod shaped in structure. On the basis of their arrangement they are of following types.
b. Streptobacillus: large numbers of bacilli bacteria are connected end to end
with each other farming an elongated rod shaped structure called
streptobacilli.
c. Palisade Bacilli : large numbers of bacilli bacteria are placed one over
other forming a stalk rod like structure called palisade Bacillus.
d. Vibrio : Morphologically comma (,) shaped bacteria are called Vibrio.
e. Spirillum: They are spirally coiled bacteria.
f. Stalked bacteria : They are small stalk-like structures on the outer surface of a
cell.
g. Mycelial bacteria : They are branched or unbranched aseptate filaments like
structure.
h. Budding bacteria: They bear small buds on the outer surface of the cell.
Gram positive and gram negative bacteria: For the identification of gram positive and gram negative bacteria, first of all bacteria are stained with alkaline crystal voilet solution (gram' s stain) and again stained with 0.5% iodine solution and after this washed with absolute alcohol. If the colour of bacteria turns into purple or violet, they are called gram positive bacteria. If they become colourless after washing absolute alcohol, they are called gram negative bacteria.
Gram positive : Bacteria which have blue color crystal violet dye after washing
by absolute alcohol are called gram positive bacteria. They have thick cell walls
without lipids. E.g. Bacillus, Clostridium.
Gram Negative: Bacteria which lose blue color crystal violet dye after washing
by absolute alcohol are called gram negative bacteria. They have thin cell walls
with lipids. E.g. Salmonella, Escherichia, Azotobacter, etc.
Structure of bacteria
Cell wall: it is thick and rigid outermost covering. it provides definite shape and
rigidity to the cell. It is made of acetyl glucosamine, acetyl muramic acid and
Diamino pimelic acid. On the outer surface of the cell wall there is mucilaginous
covering which protects the bacteria from high temperature and external harmful
agents. The thin mucilage covering is called slime layer. While thick mucilage
covering is called a capsule.
Cell membrane: It is thin, delicate, selectively permeable membrane which
separates the cell wall with cytoplasm. On the inner side of a cell membrane
large no. of small pieces of membrane called respiratory chain, it is found which
bears respiratory enzymes.
Flagella: They are microtubular structures developed from the inner side of the
cell membrane. Each flagellum bears a basal body, Hooke and filament. It is
made up of only a protein called flagellin.
Pilli : They are microtubular outgrowth developed from cell membranes.
Basically it is concerned for aeration in a bacteria cell and it also helps in the
formation of a conjugation tube during the conjugation of bacteria.
Mesosome : It is semicircular in structure and formed due to the ingrowth of cell
membrane. It bears a large no. infoldings of cell membrane like structure for the
separation of daughter DNAs after the replication of nuclear DNA during cell
division of bacteria.
Nuclear DNA : It is highly coiled double stranded naked DNA which acts as a
nuclear body and carries all genetic information.
Gas vacuoles : It consists of large no. of hexagonal bodies filled with gas. It
takes part in buoyancy regulation of bacterial cells.
Chromatophore : They are disc-like structures and are found in autotrophic
bacteria which bear photosynthetic pigments.
Ribosome : Small sized ribosomes called 70S ribosomes are found. They take
part in protein synthesis.
Reserve food : They are fat globules, Protein crystals, a-granules, b-granules,
etc. found as reserve food in cells.
Extra-nuclear DNA : They are circular DNAs found in cytoplasm which have self
replicating capacity and carry genetic characters. They may be plasmid or
cosmid.
Nutrition of Bacteria.
Basically in bacteria 2 types of nutrition are found. They are:
I)Autotrophic nutrition
II) Heterotrophic nutrition
I) Autotrophic nutrition
In this type of nutrition, bacteria can synthesize their own food material. On
the basis of technique of synthesis of organic material, they are divided into two
types:
a.) Photosynthetic bacteria
These bacteria bear photosynthetic pigments and synthesize food by the
pigments by the process of photosynthesis.
These photosynthetic bacteria are of three types:
- Green sulphur bacteria
- Purple sulphur bacteria
- Non sulphur purple bacteria
They bear chlorobium chlorophyll as photosynthetic pigment and they use H2S
as an electron donor. In this case during photosynthesis the sulphur is released
out as by product and is deposited extracellularly.
6CO2 + 12H2S------sunlight------≻ C6H12O6 + 6H2O + 12S
chlorophyll
E.g: Chlorobium limicola , Pelodictyon Calthorchoris
Purple sulphur bacteria
This bacteria bears bacterio-chlorophyll and carotenoid as photosynthetic
pigments. The majority of them generally use H2S as electron donor; the
byproduct sulphur is deposited intracellularly.
E.g.Chromatium okenii
Non sulphur purple bacteria
They bear bacteriochlorophyll as photosynthetic pigments and they use
organic compounds as hydrogen Donor. So they don't release sulphur as a by -
product.
E.g.Rhodospirillum rubrum
6CO2+12CH3CHOHCH3------sunlight------≻ C6H12O6+2H12O6+2CH3COCH3+6H2O
bacteriochlorophyll
b.) Chemosynthetic bacteria
These bacteria don't have photosynthetic pigments and can’t take part in
photosynthesis but they are autotrophic type because these bacteria oxidize the
medium in which they live and the release energy during Oxidation is used for
synthesis of their own food material. they are of different types:
i) Sulphur bacteria
ii) Iron bacteria
iii) Methane bacteria
i)Sulphur bacteria
Colour sulphur bacteria oxidize to sulphur with the releasing of energy. E.g
Thiobacillus thiooxidans Beggiatoa H2S+ 1/2O2-------≻ H2O+S+ Energy
ii) Iron bacteria
These bacteria oxidise ferrous form of iron to ferric form which releases out of
energy.
Fe++ - e ------> Fe+++ + energy
E.g. Thioxidans, Thiobacillus ferro-oxidans
iii) Methane bacteria
They oxidize Methane to CO2 and H2O by releasing energy.
CH4+2O2 + 2H2O --------> CO2+ 2H2O+ energy
E.g. Methanomonas
II) Heterotrophic nutrition
In this type of Nutrition bacteria cannot synthesise their own food material But
are dependent upon the source of prepared food. they are of different types:
a.) Parasitic bacteria: they get the ready-made food from the living host.
mostly they are of pathogenic form. E.g. Vibrio cholerae, Salmonella typhi
b.) Symbiotic bacteria: they are found in the root nodules of leguminous
absent fixing the free atmospheric nitrogen into ammonium compounds in the
soil for plants, which in turn provide shelter and Carbohydrates to the bacteria.
E.g. Rhizobium
c.) saprophytic bacteria: they use dead and decaying organic matter as their
food They break down Complex organic compounds into simpler in organic form
and they use these inorganic substances as their basic
requirements. E.g Lactobacillus acidus
Economic importance:
Useful activities of bacteria:
1.) Economic importance in the field of agriculture:
Some bacteria play the main role to increase the fertility of the soil
directly or indirectly, these bacteria increase the amount of required
nutrients of the plant in the soil.
a.) N2 fixing bacteria
b.) Nitrifying bacteria
c.) Ammonifying bacteria
a.)N2 fixing bacteria: these bacteria absorb atmosphere N2 and convert it into
nitrogen compounds used by plants as the required nutrients. They are two
types:
i.) Free living N2 bacteria: These bacteria are found freely in the soil.They
absorb atmospheric and N2 and convert it into nitrogenous compound. After the
death and decay of of this bacteria this compound mix in the soil and fertility of
the soil increases. E.g Azotobacter
ii.) Symbiotic N2 fixing bacteria : They are found in root nodules of
leguminous plants. They absorb atmospheric and N2 and convert it into
nitrogenous compounds. After the death and decay of leguminous plants the
nitrogenous compound mix in the soil and fertility of the soil is increased. E.g.
Rhizobium leguminosarum.
b.) Nitrifying bacteria: these bacteria are of two types:
i) Nitrite bacteria
ii)Nitrate bacteria
i.) Nitrite bacteria: convert and ammonium compounds into nitrite.
Ammonia----- Nitrosomonas-----≻ Nitrite
ii.) Nitrate bacteria: convert nitrite into nitrate. These nitrate compounds mix in
the soil and fertility of the soil increases.
Nitrite------- Nitrobacter -----≻Nitrate
c.) Ammonifying bacteria: Saprophytic bacteria break down protein into amino
acid then ammonifying bacteria release Ammonia gas from amino acids. Now
Ammonia reacts with CO2 and H2O to form ammonium carbonate.
2NH3 + CO2 + H2O---------≻ (NH3)2 CO3
Due to the formation of Ammonium carbonate fertility of a soil is increased.
Eg., Bacillus mycoides
d.)Disposal of sewage: Some bacteria break down organic matter of sewage
waste to harmless soluble inorganic matter, process it called mineralization. It
was separated into liquid and Sludge. Sludge later is used as fertilizer.
2.Economic importance in field industry
Industrial Products acid as well as alcohol are produced from bacteria.
i.) Lactic acid---- Lactobacillus acitus
ii.) Acetic acid ---- Acetobacter aceti
iii.) Propionic alcohol ---- Propionibacterium
3. In the field of medicine
Medicine Bacteria
i.) Streptomycin Streptomyces grisens
ii.) Chloromycetin Streptomyces venezuelae
iii.)Polymyxin Bacillus polymyxa
4. Decay of organic matter and reduction of pollution
Saprophytic bacteria cause the decaying of dead organisms. Then
complete inorganic compounds are decomposed into simple inorganic forms by
these bacteria. So bacteria play a major role in reducing environmental pollution.
So these bacteria are called “Nature’s Scavengers”.
Harmful activities
Some activities of bacteria are highly harmful to human beings as well as
different plants.
1.) Disease to animals : Some bacteria are serious to human beings.eg.,
Disease Bacteria
Cholera Vibrio cholerae
Diarrhoea Escherichia coli
Typhoid Salmonella typhi
2.)Disease to plants: Some bacteria cause serious disease to plants.
Disease Bacteria
Citrus Canker Xanthomonas citri
Ring rot of potatoes Corynebacterium sepedonicium
Black rot of cabbage Xanthomonas campestris
3.) Food poisoning: Some bacteria like Staphylococcus aureus make our
food poisonous.
4.)Reduction of fertility of soil: Denitrifying bacteria break down the
nitrogenous compound of soil and cause the releasing of N2 gas from this
compounds. Due to this reason, fertility of soil is decreased.
E.g. Micrococcus denitrificans
Hope this will help you a lot.
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