MAKEUP

 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. 

 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.