Bacteria Structure

The structure, size and arrangement of bacterial cells consitute their
morphology. (Bacteria Structure)

The various morphological features are
1. They are spherical or rod like or spiral shaped.
2. The arrangement of cells in pairs, clusters, chains, trichomes and filaments
etc.
3. The appendages are visible by special staining techniques or by electron
microscopy. (Bacteria Structure)

The above three features represent the gross morphological
characteristics, which are of taxonomic importance in bacterial species
identification. In addition, the bacterial cells possess elaborate internal
structures, which constitute microbial cytology and bacterial anatomy. (Bacteria Structure)

Bacterial Culture

All bacteria need nutrients for their growth. They need a nutrient
medium for their growth and culture. A bacteriological medium is composed Bacterial transformation is a process in which cell free or naked DNA
containing the genetic information is transferred from one bacterial cell to
another. It was discovered by an English health officer, Griffith in 1928. The
transforming principle was identified as DNA by Avery Macleod and Mc
Carthy in 1944.

In transduction, a bacteriophages acts as a vector, transfering a portion
of DNA from one bacterium (donor) to another (recepient). If all fragments
of bacterial DNA have a chance to enter a transducing phage, the
process is called Generalized transduction. On the contrary if a few restricted
genes of the bacterial chromosomes are transduced by bacteriophage,
it is called specialized transduction.

Related Topics in Zoology:

Bio Zoology All Important Topics

1. Microbiology Introduction and History of Medical Microbiology
   

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2. Pasteur, Koch, Lister
   

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3. Structure of Viruses
   

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4. Viral genetics
   

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5. Virus Culture
   

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6. Viral Diseases
   

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7. Bacteria Structure Culture
   

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8. Bacterial Genetics
   

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9. Bacterial Diseases
   

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10. Protozoan microbiology
    

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11. Pathogenecity of Microorganisms
    

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12. Antimicrobial Resistance
    

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13. Antibiotics and Chemotherapy
    

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14. AIDS – HIV

Viral Diseases

A. Cancer and Viruses

Viruses have been identified as one of the causative agents for
cancer or tumour. Such tumour inducing viruses are called oncogenic
viruses. Adenoviruses, polioma virus, simian virus 40 (SV 40), Epstein-Barr
virus (EBV) ( a herpes virus) are oncogenic DNA viruses. The RNA sarcoma
viruses are oncogenic RNA viruses (eg., Rous sarcoma). Viral Diseases

B. Rabies Virus and Rabies disease

Rabies virus belongs to the rhabdovirus family. It is a parasite of
domestic and wild mammals. The transmission to humans occurs through the
bite of an infected animal. Dogs, cats, bats, are the mammalian animal sources
for the rabies virus.
In humans, the symptoms of rabies are severe headache, high fever,
alternating excitement and depression, muscular spasms in throat and chest,
hydrophobia etc. The incubation time in humans is usually about 3 to 8 weeks
but it may also vary. If untreated the mortality rate from rabies is 100 percent.
The new rabies vaccine was discovered in 1980. It is an inactivated
vaccine prepared from the virus propagated in cultures of diploid human
cells. This vaccine is both safe and highly immunogenic. Viral Diseases

C. Pox virus

Pox viruses are the largest of all viruses and are brick shaped. They
contain double stranded DNA, protein and lipid. They have a dum bell shaped
nucleoid surrounded by two membrane layers.
Variola virus is called the small pox virus. It is transmitted by droplet
infection either directly from the infected person or by handling articles
infected by the patient. Small pox is completely eradicated. The small pox
vaccine consists of vaccinia, closely related to variola. It gives protection
both by humoral and cell mediated immunity.
Other pox viruses are chicken pox and measles viruses. Viral Diseases

D. Hepatitis-B

Hepatitis B virus (HBV) is an enveloped virus with a double stranded
DNA. This causes jaundice and hepatic carcinoma. This disease is deadly
and more infective than AIDS. HBV vaccine consists of purified HBV Ag
(Australian antigen) obtained from the blood serum of apparently healthy
carriers. Viral Diseases

Related Topics in Zoology:

Bio Zoology All Important Topics

1. Microbiology Introduction and History of Medical Microbiology
   

   ---

2. Pasteur, Koch, Lister
   

   ---

3. Structure of Viruses
   

   ---

4. Viral genetics
   

   ---

5. Virus Culture
   

   ---

6. Viral Diseases
   

   ---

7. Bacteria Structure Culture
   

   ---

8. Bacterial Genetics
   

   ---

9. Bacterial Diseases
   

   ---

10. Protozoan microbiology
    

    ---

11. Pathogenecity of Microorganisms
    

    ---

12. Antimicrobial Resistance
    

    ---

13. Antibiotics and Chemotherapy
    

    ---

14. AIDS – HIV

Virus Culture

Cultivation (culture) of Animal viruses (Virus Culture)

Viruses can grow only in living cells. However the culture of viruses
is possible nowadays. The most economical and convenient method of
cultivating a wide variety of animal viruses is the ‘chicken embryo technique’.
In this technique, fertile chicken eggs incubated for 5 to 12 days are
inoculated with the virus particles through the shell, aseptically. The opening
may be sealed with paraffin wax. The eggs incubated at 36oC are ideal sources
for the growth of viruses.

Chick embryos contain several different types of cells in which
various viruses will undergo replication. The yolk sac is a general ideal
medium for the growth of viruses.
Viral cultures are of three types viz., Primary cell cultures, diploid
cell strains and continuous cell lines.

1. Primary culture: Virus Culture

Primary cell culture are derived from normal tissue of an animal such
as mouse, hamster, chicken and monkey or a human being. When cells from
these tissues are processed and cultured the first monolayer is referred to as
the primary culture. A monolayer is a confluent layer of cells covering the
surface of a culture vessel.

2. Diploid cell strain: Virus Culture

Diploid cell strains are derived by primary cell cultures from a
specific tissues like lung or kidney which is of embryonic origin. These
diploid cells are the most employed host of choice for the production of
human vaccine virus.

3. Continuous cell lines: Virus Culture

Continuous cell lines are capable of an infinite number of doublings.
Such cell lines may arise with the mutation of a cell strain or more commonly from the established cell cultures from malignant tissue. Many viruses, which
are difficult or impossible to grow have been cultured in continuous cell lines.

Related Topics in Zoology:

Bio Zoology All Important Topics

1. Microbiology Introduction and History of Medical Microbiology
   

   ---

2. Pasteur, Koch, Lister
   

   ---

3. Structure of Viruses
   

   ---

4. Viral genetics
   

   ---

5. Virus Culture
   

   ---

6. Viral Diseases
   

   ---

7. Bacteria Structure Culture
   

   ---

8. Bacterial Genetics
   

   ---

9. Bacterial Diseases
   

   ---

10. Protozoan microbiology
    

    ---

11. Pathogenecity of Microorganisms
    

    ---

12. Antimicrobial Resistance
    

    ---

13. Antibiotics and Chemotherapy
    

    ---

14. AIDS – HIV

Viral genetics

The viral genome contains all the genetic information either as DNA
or RNA. but never both. The proportion of nucleic acid in a virion varies
from 1 % as in influenza virus to about 50%, as in certain phages. Smaller
viruses like paraviruses may have 3 to 4 genes while larger viruses like
herpes and pox may have several hundred genes. Viral genetics

Virions contain only a single copy of the nucleic acid. Hence they are called haploid viruses. The only exception is the retroviruses, which are said to be diploid as they contain two identical single-stranded RNA genomes. The virions are called the infectious particles. Viral genetics

The structure of nucleic acid in the virion may be either linear or
circular. The DNA of most animal viruses in a linear molecule. In some plant
viruses the genome is a circular RNA. But the RNA in animal viruses exists
only as linear double stranded or single stranded molecule. Viral genetics

Related Topics in Zoology:

Bio Zoology All Important Topics

1. Microbiology Introduction and History of Medical Microbiology
   

   ---

2. Pasteur, Koch, Lister
   

   ---

3. Structure of Viruses
   

   ---

4. Viral genetics
   

   ---

5. Virus Culture
   

   ---

6. Viral Diseases
   

   ---

7. Bacteria Structure Culture
   

   ---

8. Bacterial Genetics
   

   ---

9. Bacterial Diseases
   

   ---

10. Protozoan microbiology
    

    ---

11. Pathogenecity of Microorganisms
    

    ---

12. Antimicrobial Resistance
    

    ---

13. Antibiotics and Chemotherapy
    

    ---

14. AIDS – HIV

Viruses

Structure of Viruses :- Viruses are infectious agents. They are much smaller than the bacteria. Their approximate size ranges from 20 to 300 nm. Viruses are
incapable of independent growth in artificial media. They can grow only in
animal or plant cells or in microorganisms. Hence they are referred to as
obligate intracellular parasites. They reproduce in these cells by replication.

Replication is a process in which many copies or replicas of the viral
component are assembled and made to represent the progeny. They lack
metabolic machinery of their own to generate energy or to synthesize
proteins. They depend on the host cells to carry out these vital functions. The
bacterial viruses are called bacteriophages. These viruses infect the
bacteria and multiply inside the bacterial body and cause the lysis of bacteria
(lytic cycle) or integrate themselves with the bacterial genome (lysogeny).

Structure of Viruses:

Animal and plant viruses are composed of a central core of nucleic
acids surrounded by a protein covering called capsid. The capsid is made up
of units called capsomeres. Viruses exhibit a characteristic symmetry,

1. Spherical viruses are isohedral, 2. Rod shaped viruses are helical in
symmetry. Certain group of viruses are complex in symmetry.

Some animal viruses, in addition to the nucleocapsid structure
contain an outer membrane like structure called the envelope. The envelope
is made up of lipoproteins. The envelope conceals the symmetry of viruses.
Virions with envelopes are sensitive to lipid solvents such as ether and
chloroform. On the other hand, the naked virions are not affected by the
lipid solvents.

Isohedral viruses such as adeno viruses, SV15, polio viruses and
blue tongued viruses are spherical in shape and their surface is a lattice with
identical triangular units.

Helical surface symmetry and structure are characteristic of tobacco
mosaic virus(TMV) and animal viruses that cause diseases such as measles,
mumps, influenza and rabies. In these, the nucleo capsid is a flexible
structure packed within a fringed lipoprotein envelope. The fringes are made
of glycoproteins. In TMV the nucleic acid core is covered by a capsid
consisting of closely packed capsomeres arranged in a helix.

Complex or uncertain symmetry is seen in Pox viruses, T-bacteriophages,.
These have different proteins and lipoproteins.

Related Topics in Zoology:

Bio Zoology All Important Topics

1. Microbiology Introduction and History of Medical Microbiology
   

   ---

2. Pasteur, Koch, Lister
   

   ---

3. Structure of Viruses
   

   ---

4. Viral genetics
   

   ---

5. Virus Culture
   

   ---

6. Viral Diseases
   

   ---

7. Bacteria Structure Culture
   

   ---

8. Bacterial Genetics
   

   ---

9. Bacterial Diseases
   

   ---

10. Protozoan microbiology
    

    ---

11. Pathogenecity of Microorganisms
    

    ---

12. Antimicrobial Resistance
    

    ---

13. Antibiotics and Chemotherapy
    

    ---

14. AIDS – HIV