Module 3

Microbial : Acellular Microbes

Virus

Virus

They obligate intracellular pathogens. They also infect humans, animals, plants, fungi, protozoa, algae, and bacterial cells.

Oncogenic Viruses/Oncoviruses

These are viruses which causes specific types of cancer

Virions

It is a complete virus particle that is very small and simple in structure. They have complete DNA or RNA. They are extremely small particles that demands an electron microscope to be viewed (10nm - 300nm).

5 Specific Properties that Distinguish Viruses from Living Cells

1. Possess DNA or RNA but not both.

2. Unable to replicate on their own.

3. Do not divide by binary fission, mitosis, or meiosis. Lytic Cycle only

4. Lacks genes and enzymes necessary for energy production.

Genetic Material

It consists of a genome of either DNA or RNA but not both that is surrounded by a capsid.

Enveloped Viruses

They have an outer envelope composed of lipids and polysaccharides and molecules of proteins.

Bacterial Viruses

They may have tail, sheath, and tail fibers.

Polyhedral/Icosahedral Virus

20 evenly shaped triangular vertices; multi-sided surfaces.

Helical Virus

Rod-shaped

Complex Virus

Composed of many shapes

Rabies Virus

Bullet-shaped

Coevolution Theory

Viruses originated from the primordial soup and coevolved with bacteria and archaea.

Retrograde Evolution Theory

Viruses are a product of invasion. They evolved from free-living prokaryotes that invaded other living organisms, and gradually lost function provided by the host cell.

Escaped Gene Theory

Viruses are from pieces/fragments of host cell RNA or DNA that have escaped from living cells and are no longer under cellular control.

Bacteriophages

These are viruses that infect bacteria

Virulent Bacteriophage

Always causes a lytic cycle, which ends with the destruction of bacteria.

Lysogenic Conversion

The bacterial cell will exhibit new properties

Transduction

It means “to carry across”. The genetic materials are carried from one bacterial cell to the other.

Animal Viruses

Viruses that infect animals including humans.

Steps in the Multiplication Process

1. Attachment/Adsorption

2. Penetration

3. Uncoating

4. Biosynthesis

5. Assembly

6. Release

A Perfect Unicorn Bake Amazing Rainbow

Attachment/Adsorption

Animal viruses can only attach to and invade cells bearing appropriate surface receptors.

Penetration

The entire virion usually enters the host cells, sometimes the host cell phagocytize the virus.

Uncoating

The viral nucleic acid escapes from the capsid. from this point on, the viral nucleic acid dictates what occurs within the host cell.

Biosynthesis

The step whereby many viral proteins are produced.

Assembly

Involves fitting the virus pieces together to produce a complete virion

Release

Viruses escape from the host cell’s cytoplasm by budding and becoming surrounded by pieces of membrane, thus becoming a complete virus.

Epstein-Barr virus

Virus that causes nasopharyngeal carcinoma

Hepatitis B and C virus

Virus that causes hepatocellular cancer

Herpesvirus 8

Virus that causes Kaposi Sarcoma; patches of abnormal tissue under the skin, mouth lining, nose, throat, lymph nodes, and other organs.

Human papillomaviruses

Virus that causes cervical carcinoma

T-lymphotropic virus type 1

Virus that causes T-cell leukemia

Human Immunodeficiency Virus

Virus that causes AIDS.

Mimivirus

Virus that mimics bacteria. They were recovered from amoeba. They have extremely large double-stranded DNA virus and contains some RNA molecules.

Steps in the Lytic Cycle Process

1. Attachment/Adsorption

2. Penetration

3. Biosynthesis

4. Assembly

5. Release

Ask Peter Barker to Assess Respiration (mnemonics)

Temperate Bacteriophage

They are also called Lysogenic phages. They do not immediately initiate lytic cycle. Rather, the phage’s DNA is integrated into bacterial cell chromosomes and remains dormant for generations.

Lysogenic Conversion

When temperate phages inject their DNA to the bacterial cell, it is integrated into the bacterial chromosome and does not cause lysis. The bacterial cell can produce gene products coded for by the prophage genes.

Lysogeny

The phage genome is present into the cell but is not causing the lytic cycle to occur. All that remains in the phage is its DNA; in this form, the phage is called prophage.

Lysogenic Cell/Lysogenic Bacterium

Bacterial cell containing the prophage. Each time the lysogenic cell undergoes binary fission, the phage DNA, since it manipulates the bacteria, is replicated.

Plant Viruses

They infect plants through vector transfer.

Viroids

They have no capsids. They usually cause plant diseases and consists of a short, naked fragment of single-stranded RNA that can interfere with the metabolism of plant cells and stunt the growth of plants, and sometimes can be fatal to plants.

Prions

These are small infectious proteins that cause fatal neurological diseases in animals.