AGRI Grovestudies
The major differences between prokaryotic and eukaryotic microorganisms
Prokaryotic
Cellular organization :- Cell walls made up of
peptidoglycans.
Ribosomes-70S
Flagella consist of
single protein called
flagellin.
Genetic materials and
replication : No nuclear membrane
present, DNA free in
the cytoplasm
May contain extrachromosomal DNA
called plasmids
Cell division by
binary fission
Transfer of genetic
information occurs
by conjugation,
transduction and
transformation.
Eukaryotics
Cell walls made up of
polysaccharides either
cellulose (algae) or
chitin (fungi)
Ribosomes-80S
(mitochondrial and
chloroplast ribosomes
are 70S)
Flagella have more
complex structure with
9+2 microtubular
arrangement
True Membrane bound
nucleus is present with
DNA in it.
Plasmids rarely
found .
Cell division by
mitosis
Exchange of genetic
information occurs
during sexual
reproduction.
Meiosis takes place
for the production of
haploid cells
(gametes).
Microbiology
Microbiology is the study of living organisms of microscopic size, which include bacteria, fungi, algae and protozoa and the infectious agents like viruses.
It is concerned with their form, structure, reproduction, physiology, metabolism and classification.
Role of microbiology in agriculture
Microbiology in general, has very diverse utility in
agriculture, horticulture, and forestry and hence studied
as a different branch termed as agriculture microbiology.
A big number of harmful microorganisms called
pathogens are responsible for majority of plant diseases.
So, basic knowledge of microbiology is requires to
understand the causes,
Plant Pathology: Plant pathology is basically the study
of microorganisms that cause disease in plants. The
microorganisms which cause diseases in the plants are
called as plant pathogens.
Biopesticides :-
The term
biopesticides are defined as the compounds derived from some
living organisms and used to manage insect-pests by means of
specific biological lethal effects.
Genetic Engineering
Genetic engineering is the process of using recombinant DNA (rDNA) technology to alter the genetic makeup of an organism.
Food and Fermentation technology
Microorganisms have been extensively used to aid up food
industries are- Beer and wine production by yeast, bread
making, processing of milk to dairy products by lactic acid.
Bacterial Genetics :-
Genetics is the study of heredity and variations.
Like other living organisms, bacteria also multiply and
pass on their characteristics from generation to
generation.
Bacteria reproduce by binary fission.
Bacteria can transfer genes from one strain to another by
three different mechanisms: transformation, conjugation
and transduction.
Transformation
Bacterial transformation is a process of horizontal gene transfer by which some bacteria take up foreign genetic material (naked DNA) from the environment.
DNA is integrated into the recipient genome
by homologous recombination.
DNA material can be transferred between different
strains of bacteria in a process that is called horizontal
gene transfer.
Griffith Experiment & Transforming Principle
Transformation in bacteria was first demonstrated in
1928 by the British bacteriologist Frederick Griffith.
Griffith was interested in determining whether
injections of heat-killed bacteria could be used to
vaccinate mice against pneumonia.
he discovered that a non-virulent strain
of Streptococcus pneumoniae could be made virulent
after being exposed to heat-killed virulent strains.
Fredrick Griffith (1928) found that there were two
different strains of bacteria Streptococcus pneumoniae
(also known as the pneumococcus)
a) An ‘S’ or smooth coat strain of it, usually
surrounded by a gummy capsule made of a
polysaccharide.
b) An ‘R’ or rough strain, surface of its colonies is
wrinkled and rough ("R"). With no capsule, the
bacteria also do not possess virulence i.e. the strain is
non lethal to mice.
c) Griffith observed that on injecting mice with small number of avirulent ‘R’cells together with heat killed ‘S’ cells, mice died. thus it was concluded that, there was some material in the heat killed ‘S’ strain that was responsible for transforming the ‘R’ strain into lethal form.
c) Griffith observed that on injecting mice with small number of avirulent ‘R’cells together with heat killed ‘S’ cells, mice died. thus it was concluded that, there was some material in the heat killed ‘S’ strain that was responsible for transforming the ‘R’ strain into lethal form.
Conjugation
In conjugation, DNA is transferred through a
tube between two bacteria cells.
Conjugation is the technique of transfer of genetic material from one bacteria to another placed in contact.
This method was proposed by Lederberg and Tatum. They discovered that the F-factor can move between E.coli cells and proposed the concept of conjugation.
Bacterial conjugation involves the following steps:
Pilus Formation
The donor cells (F+ cells) form a sex pilus and begin contact with an F- recipient cell.
Physical contact Between Donar and Recipient Cell
The pilus forms a conjugation tube and enables direct contact between the donor and the recipient cells.
Transfer of F-Plasmid
The F-factor opens at the origin of replication. One strand is cut at the origin of replication, and the 5’ end enters the recipient cell.
Synthesis of Complementry Strands
The donor and the recipient strand both contain a single strand of the F-plasmid .
The recipient cell now contains a copy of F plasmid and becomes a donor cell.
Bacterial Transduction
Transduction is the process of transfer of genes from the recipient to the donor through bacteriophage.
A bacteriophage is a type of virus that infects bacteria.
Transduction is of two types:
Generalized Transduction
Specialized Transduction
Generalized Transduction
Generalized transduction is the process by which any bacterial gene is transferred to another bacterium via a bacteriophage.
