Chapter – 9
Kingdom Monera
BACTERIA
DISCOVERY
Bacteria was discovered by A.V. Leuwenhoek in 1676.
STRUCTURE OF BACTERIA
Bacteria are
smallest and simplest living organism measures from 0.2m to 2 micron in breadth
and 2 to 10 micron in length. They are strictly unicellular but some species
remain associated with each other after cell division and form colonies.
A generalized bacterial cell consists of following structures.
(1)FLAGELLA
They are extremely thin appendages, which originate from
basal body, a structure in the cytoplasm beneath cell membrane. Flagella help
in bacterial locomotion.
(2)PILLI
They are hollow, filamentous flagella like appendages,
which help in conjugation but not in locomotion.
(3)CAPSULE
It is a protective sheath made up of polysaccharides and
proteins. It provides greater pathogenicity and protects bacteria against
phagocytosis.
(4) CELL WALL
Bacterial cell wall mostly made up of amino acids, sugar
and chitin. It surrounds the cell membrane, determine shape and protects bacteria
from osmotic lyses. Most bacteria have a unique macromolecule called
Peptidoglycan in addition to it. Sugar molecules, teichoic acid, glyco proteins
and lipo polysaccharide are also present.
(5)CELL MEMBRANE
§ It is present inside the cell wall attached to it at few places
containing many pores.
§ It is made up of lipids and proteins.
§ It acts as a respiratory structure.
(6)CYTOPLASM
Bacterial cytoplasm is granular containing many small
vacuoles, glycogen particles and ribosomes.
(7)MESOSOMES
§ These are the invaginations of the cell membrane into the
cytoplasm.
§ They are in the form of vesicles, tubules or lamella.
§ They help in the DNA replication, cell division, respiration and
export of enzyme.
(8)BACTERIAL HEREDITARY
MATERIAL
§ Bacterial hereditary material DNA is found as concentrated
structures called Bacterial chromosomes or chromatin bodies. It is mostly
scattered in the cytoplasm.
§ A small fragment of extra chromosomal circular DNA, called
Plasmid is also present.
FIGURE 6.1 (FROM TEXT BOOK)
CLASSIFICATION OF BACTERIA
ON THE BASIS OF SHAPE
On the basis of shape bacteria can be divided into four categories.
(1)COCCI
§ These are spherical or rounded bacteria presents in the form of
mono, diplo or streptococcus form.
§ They are non-flagellated and cannot move from one place to
another place.
FIGURE (FROM TEXT BOOK)
(2)BACILLI
§ Bacilli are rod shaped bacteria, can be present in the form of
diplo or streplobacilli.
§ They may be flagellated and can move from one place to another.
FIGURE (FROM TEXT
BOOK)
(3)SPIRILLA
§ These are spiral or cork, screw shape bacteria also known as
spirochetes.
§ It includes chlamydia and rekettia.
FIGURE (FROM TEXT
BOOK)
(4)VIBRIO OR COMMA
§ These are slightly curved bacteria like vibrio cholera.
§ They may be flagellated and can move.
ON THE BASIS OF RESPIRATION
On the basis of respiration bacteria can be divided into two main types.
(1)AEROBES
Require oxygen for respiration.
(2)ANAEROBES
Respire with out oxygen
Sub-classes of this classification are as follow:
(A)FACULTATIVE BACTERIA
Respire with or without oxygen.
(B)MICRO AEROPHILIC BACTERIA
Require low concentration of oxygen for growth
(C)OBLIGATE ANAEROBES
These bacteria only survive in absence of oxygen.
(D)FACULTATIVE ANAEROBES
These bacteria use oxygen but can respire with out it .
bThese bacteria only survive in the
presence of oxygen.
ON THE BASIS OF NUTRITION
Bacteria can be divided into four main types on the basis of nutrition. Which
are as follow.
(1)SAPROTROPHIC BACTERIA
§ These bacteria depend on the dead organic matter for their
nutrition.
§ They are mostly present in the humus of soil and posses large
number of enzymes that convert complex substances of humus to simpler
compounds.
(2)SYMBIOTIC BACTERIA
§ These bacteria are found associated with other living organism.
§ They obtain their food from the host without harming it. E.g.
Rizobium redicicola (Symbionts in the root nodules of pea family plants).
(3)PARASITIC BACTERIA
§ These bacteria grow inside the tissues of other living organism
§ They obtain food at the expense of their host.
§ These bacteria lack certain complex system of enzymes therefore
they usually depend upon host cell. E.g. Pneumococcus, Mycobacterium
tuberculosis, Salmonella typhi.
(4)AUTOTROPHIC BACTERIA
§ These bacteria can sythesize organic compound from simple
inorganic substances.
Autotrophic
bacteria can be divided into photosynthetic or chemosynthetic.
(A)PHOTOSYNTHETIC
§ These bacteria contain green pigment chlorophyll, which is known
as bacterial chlorophyll, or chlorobium chlorophyll.
§ These pigments are present in mesosomes (invagination of the
cell membrane in the cytoplasm)
§ These bacteria utilize H2S during photosynthesis instead of
water and liberate sulphur instead of oxygen.
§ sunlight
(B) CHEMOSYNTHETIC
§ These bacteria obtain their energy from oxidation of some
inorganic substances like iron, hydrogen, nitrogen and sulphur compounds.
LOCOMOTION IN BACTERIA
§ Some bacteria can move from one place to another with the help
of a wipe like structure flagella.
§ Flagella allow bacteria to disperse into new habitats, to
migrate towards nutrients and to leave unfavorable environment.
§ Flagellated bacteria show orientation towards various stimuli, a
behavior called Taxis.
§ Some bacteria are chemo tactic, phototectic or magnetotatic.
GROWTH IN BACTERIA
In favorable
conditions bacteria can grow, very rapidly. There are some factors affecting
growth of bacteria such as Temperature, nutrient availability, PH and ion
concentration. Bacterial growth can be divided into four main phases, which are
as follows
(1)LAG PHASE
It is inactive phase during which bacteria prepare them
for division.
(2)LOG PHASE
In this phase bacteria grow and multiply very rapidly.
(3)STATIONARY PHASE
In this phase bacterial multiplication is equal to
bacteria death rate.
(4)DECLINE/DEATH PHASE
In this phase death is more rapid then multiplication
rate.
REPRODUCTION IN BACTERIA
Usually asexual
reproduction is present in bacteria which is as follow
FISSION
Fission is the fastest mode of bacterial asexual reproduction (Binary Fission)
§ It usually takes place in favorable conditions.
§ Hereditary material DNA in the form of chromatin body
replicates.
§ After the replication of hereditary material a constriction
appears in the middle of the cell, which later splits it into two parts.
§ Newly form bacterial cells grow in size and form nature
bacterial cells.
§ The single fission takes place in 20-30 minutes.
ENDOSPORE FORMATION
§ It is the method of bacterial survival under unfavorable
conditions. Following are the main characters of this process.
§ During this process, the whole protoplasmic content gets shrink
into a small mass.
§ A cyst is formed inside the parental wall around constricted
protoplasm to form endospore.
§ On the return of favorable conditions parental wall raptures due
to decay and endospore is set free.
§ In the end, this endospore enlarges to form a mature bacterial
cell.
FIGURE 6.4 (BINARY
FISSION IN BACTERIA)
FIGURE 6.5 (FORMATION OF ENDOSPORE)
GENETIC RECOMBINATION IN BACTERIA
Genetic changes
with the help of which bacteria adopt new characteristics (drugs resistance
pathogenic ability) is known as Genetic recombination
Three types of genetic recombination are present in bacteria, which are given
as follow.
1.CONJUGATION
Simple process of genetic recombination in which genetic material is
transferred from one bacteria to another through a conjugating tube.
Conjugation in bacteria was discovered by Joshua Lederburg and Edward L.Tatum
in 1946
EXPERIMENT
J.laderberg and E.Tatum performed an interesting experiment
in order to prove conjugation in bacteria. Following are the main steps of this
experiment.
1. They selected a
wild type bacteria (E-coli) and obtain (triple nutritional mutants) different
from one another.
2. Wild-type was
capable of synthesizing six substances symbolized as A, B, C, D, E and F.
3. Mutant type I
was capable of synthesizing three substances symbolized as A, B and C but not
D, E and F.
4. Mutant type II
was capable of synthesizing three substances D,E and F but not A,B and C.
5. These mutant
type I and II were grown together in the growth medium having all the six
substances A, B, C, D, E and F.
6. After several
hours, three types of bacteria were detected after nutritional test which were,
i. Both mutant I and mutant II types.
ii. Wild type bacteria synthesizing all the six substances.
iii. A new type of bacterial strain requiring all the six substances for
growth.
In this experiment, appearance of wild type and one new type is an evidence
that conjugation had taken place.
2. TRANSDUCTION
It is the mode of genetic recombination in which genetic material is
transferred from one bacteria to another by a third party, which is usually
bacteriophage.
This process was experimentally carried out by Lederberg and Zinder in 1952.
EXPERIMENT
1. In this experiment, a bacteriophage is made to attack a
bacterium known as “donor” (D).
2. The injected DNA of bacteriophage multiply to form a large number of
daughter phages.
3. The donor bacterium (D) gives some of its genetic material “D” to the multiplying
particles.
4. The phages released from this donor bacterium contain the genetic material
of phage plus a little piece of the donor genetic material “D”.
5. These new phages then made to attack a new bacterium known as “Recipient”
(R).
6. These recipient bacterium is not destroyed like the donor in order to
reproduce normally. In this way, genetic material of the donor bacterium is
carried to the recipient bacterium by a bacteriophage and this process is known
as Transduction.
3. TRANSFORMATION
In this process, genetic information transfers from one bacteria to another by
producing a change it (undergo a change).
This type of genetic recombination was first proved by Fred Griffith in 1928.
EXPERIMENT
Griffithi injected a small quantity of R-type bacteria and
a large quantity of heat killed S-type bacteria into the same mouse.
This treatment proved fatal as mouse surprisingly suffered from Pneumonia and
died.
The autopsy of the
mouse revealed the presence of living S-type bacteria in the mouse in addition
to R-type.
From this experiment Griffith concluded that,
The live R-type bacteria had been transformed into live S-type bacteria due to
transfer of some material from dead S-type, cells.
Thus this transformation occurred due to genetic recombination in R-type
bacteria.
In his experiment,
he had been working on two strains of bacteria “Pnemococcus”. One strain is
known as smooth type (Virulent and causes Pneumonia) while the second strain is
known as (Rough type (Non-Virulent and does not cause pneumonia).
NOTE: (IMPORTANCE OF BACTERIA (USEFUL AND HARMFUL BACTERIA)FROM BOOK PAGE # 116
(OLD BOOK – 2003)
VACCINATION
DEFINITION
Inoculation of host with
inactive or weaken pathogens or pathogenic products to stimulate protective
immunity.
§ In case of subsequent natural infection with the same pathogen
the immune system easily recognized the invader and comfortably managed to
overcome the pathogen.
§ A vaccine can taken orally (Polio vaccine) or injected into the
body (Tetanus Vaccine).
IMMUNIZATION
DEFINITION
It is a process of induction of
specific immunity by injecting antigens, antibodies or immune cells.
§ Immunity can be protective or curative in nature.
§ It promotes increased immunity against specific diseases.
CYNOBACTERIA (BLUE GREEN ALGAE)
MAIN CHARACTERISTICS OF CYNOBACTERIA
§ They are prokaryotic unicellular autotrophic organisms mostly
occur in colony form.
§ They posses double layered cell wall.
§ The protoplasm differentiated into an outer colored region
chromoplasm, which contain various pigments in which chlorophyll “a” and
phycocyanin are more important.
§ Inner colorless region of the protoplasm is known as
centroplasm.
§ They are mostly aquatic (fresh water)
§ Sexual reproduction is absent.
§ Asexual reproduction takes place by means of Harmogonia,
zoospores, akinates and fragmentation.
NOSTOC
Nostoc is a typical
example of blue green algae.
STRUCTURE
§ Nostoc is a filamentous prokaryotic algae in which filaments are
intermixed in a glatinous mass-forming ball like structure known as coenobium.
§ A single filament look like a chain of beads.
§ Each filament is unbranched and has a single row of rounded or
oval cells.
§ Each cell has double layered wall, outer thick wall is made up
of cellulose mixed up with pectic compounds. While inner thin layer is made up
of cellulose only.
§ The protoplasm is differentiated into an outer colored region
(chromoplasm) and an inner colorless region (centroplasm).
§ The chromoplasm various pigments like chlorophyll,
axanthophylls, carotene, phycocyanin and phycoerythrin.
§ Ribosome’s, pseudovacuoe and reserve food in the form of
cynophyceae starch are present.
§ Hereditary material is present in cytoplasm with out the nuclear
membrane.
§ In Nostoc filaments slightly larger, colorless cells with thick
walled known as “Heterocyst” are present. The function o Heterocyst is nitrogen
fixation, food storage and multiplication of filament during unfavorable
conditions.
NUTRITION
§ It is an autotroph and prepares its food in the presence of
sunlight.
§ It also capable of fixing atmospheric nitrogen and converts it
into nitrates in order to prepare amino acids and proteins, this activity takes
place in Heterocysts.
REPRODUCTION
§ Only asexual reproduction is present which takes place by
following methods.
(1)HORMOGONIA
§ A portion of the filaments between two heterocysts is known as
Hormogonia.
§ During favorable conditions, filaments break up at the junction
of each Heterocyst.
§ The end cells of each homogonous divide to form long filaments
of Nostoc.
(2)AKINETES
§ It is the method of survival during unfavorable conditions.
§ These are non-motile spores, formed from certain vegetative
cells.
§ Each akinete contains an outer layer “exospore” and inner layer
“endospores”.
§ On the return of favorable conditions, each akinete germinates
by rupturing exospore and formed independent filaments by simple cell division.
IMPORTANCE OF CYNOBACTERIA
§ They release oxygen as a by-product during photosynthesis.
§ Many are capable of fixing atmospheric nitrogen.
§ They are first colonizers of moist soil.
§ Nostoc anabena is used as nitrogen fertilizer in agriculture due
to its nitrogen fixing ability.
MONERA
§ Discovery of bacteria A.V.Leuventoek.
§ Size of bacteria = 0.2-2 micron (breadth)
§ = 2-10 micron (length).
§ Cell wall of bacteria made up of peptidoglycan.
§ Arch bacteria do not contain peptidoglycan.
§ Bacterial replications, cell division, respiration, export of
enzymes = By means of mesosomes (invaginations of cell membrane)
§ Saprophytic bacteria form humus (important component of soil)
§ Photosynthetic bacteria = use H2S in photosynthesis instead of
water.
§ Chlorobium chlorophyll or bacterial chlorophyll discovered by
Von Nell 1930.
DIVERSITY OF LIFE
§ Father of taxonomy = Charles Linneus.
§ Genetics = final tool in classifying living organism.
§ Basic unit of Biological classification = species.
§ Five kingdom system of Robert Whittaker = 1969.
§ Discovery of Virus = Iwanosky 1892.
§ TMV Virus discover by Wendell Stanley in 1935.
§ Size of Virus = 20nm-250nm.
§ AIDS is caused by Human Immune Deficiency Virus (HIV)
§ As a result of lytic cycle of bacterio phage 100-200 daughter
phage viruses are produced.
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