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CHAPTER 21VIRUSES MONERA

• STRUCTURE

AND SHAPE• CLASSIFICATION• REPRODUCTION• RETROVIRUS• ORIGIN OF

VIRSUSES

• CLASSIFICATION• STRUCTURE• ECOLOGY/

ADAPTATION• REPRODUCTION• ECONOMIC

IMPORTANCE

• Bacteria Testing

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21:1 Structure and Shape of viruses

• Don’t possess life functions

• Composed of Protein coat and Genetic materials ( DNA or RNA)

• Most are spherical or other geometric form

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Shape of viruses• Many are spherical with

projections

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More Virus shapes

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Filamentous virusEbola

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Complex Virus Structures

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HIV MODEL

RNA

Enzymes

Core Protein Coat

Inner protein

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Virus slides

1- Influenza virus

2- Polio virus

3- Tobacco Mosaic virus

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Virus Sizes• With electron microscopy the level of

resolution is 5nm (1nm = 10-9 meters). To put this into some kind of perspective:

• an atom is about 0.2-0.3 nm in diameter• DNA is about 2nm in diameter. A small

virus• parvovirus has a diameter of about

25nm. A large virus (e.g.• poxviruses) have a diameter of up to

300nm.

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Classification of Viruses

• Grouped by the type of genetic material they have

– Single strand of DNA

– Double strands of DNA

– Single strand of RNA

– Double Strands of RNA

• Shape and size

11Virus Families• Poxviridae (pox viruses)• Parvoviridae• Reoviridae• Picornaviridae (Hepatitis A virus, foot-and-

mouth disease virus)• Togaviridae (Rubella virus)• Flaviviridae (Hepatitis C virus, yellow fever

virus)• Rhabdoviridae• Bunyaviridae (Hantaan virus)• Herpesviridae (Human Herpes Simplex

Viruses 1&2, VZV, Human

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Virus Families continued• Adenoviridae• Papovaviridae (Papillomaviruses)• Hepadnaviridae (Hepatitis B virus)• Caliciviridae• Arenaviridae• * Paramyxoviridae (Measles virus)• * Orthomyxoviridae (Influenza viruses

A-C)• * Filoviridae (Ebola virus)• * Retroviridae (HIV-1&2, HTLV-1)• * Astroviridae

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Viral Reproductions

• Since viruses are nonliving they must use a host for reproduction. The host provided all the material and energy to replicate itself.

• Viruses are very specific in which types of cell they require as host. This is why it is very difficult (but not impossible)to get a virus infection from an animal.

• Two types of reproductive cycles– Lytic cycle– Lysogenic cycle

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Lytic Cycle

• Attachments

• Entry ( injection / endocytosis )

• DNA or RNA replication

• Assembly New protein coat added

• Releasing new virus

– Lysis

– Budding

– Cell membrane channels

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Replication steps

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Movie clip showing ReplicationQuickTime™ and aVideo decompressor

are needed to see this picture.

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Lysogenic Cycle see page 508

• Attachment

• Entry

• Provirus formation

• Cell Division

• Trigger

• Lytic cycle

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Retrovirus

• The most complex RNA viruses

• During injection of their RNA they also inject a special enzyme that help in the reverse transcriptase

• See page 510

• HIV is such a virus

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ORIGIN OF VIRUSES

• The theory is that viruses originated from cells who DNA or RNA some how escaped a developed a way to reproduce as parasites.

• This would indicate that new viruses could be continually being made.

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Monera (Bacteria)

• Archaebacteria - ancient bacteria that live in extreme enviroments.

– Oxygen free environments

– salt water environments

– hot acidic waters

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Life on Mars

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Eubacteria- Heterotrophs

• Heterotrophs- decomposers

• Eubacteria - Chemosynthetic

• Eubacteria- Photosynthetic

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Bacteria structures

• Shapes

– coccus- round

– bacillus- rod shape

– spirallus- cork screw shape

• Arrangements

– diplo-

– staphylo-

– strepto-

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Shapes of Bacteria

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Coccus - Round shape

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Bacillus- Rod Shape

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Bacillus 2E. Coli sem x1815

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E.coli Sem x49,440

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Streptomyces sem x 5,510

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Spirallus bacteria

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Naming of Bacteria

• Names are a combinations of the shape and the cluster arrangements.

– Example

–diplococcus

–streptococcus

–staphylbaccillus

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A typical bacteria structure

• Prokaryotes- Lack a membrane bound nucleus.

• Cell wall- Different chemical composition than plants- complex polysaccharide (not found in eukaryotes)

• Plant cell walls contain cellulose.

• See Transparency # 44

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Structures continued• Capsule- slimy material that covers the cell

wall. Protects the bacteria.

EX. Capsule protects the cell from the white blood cells and antibodies produced by animal cells.

• Cell membrane- located just inside the cell wall. Prokaryotes lack organelles. All reactions take place in the folds of the cell membrane.

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Structure continued 2

• Cytoplasm- contains ribosome (synthesize proteins). If bacteria carry out photosynthesis chlorophyll is contained here.

• Hereditary material (DNA)- Lack a "true" nucleus. DNA is circular. Found in the nucleolid. Plamids are smaller segments of DNA.

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Structures continued 3• 6.Endospores- Formed within the

cytoplasm. Contain DNA and a small amount of cytoplasm. Form when conditions are unfavorable. Allows the bacteria to remain dormant. When conditions become favorable the bacteria will grow again. Developed this trait for survival

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Protection from Osmotic rupture

• Like most living things the concentration of water and other liquids is higher outside the organism then inside

• Most bacteria have a thick cell wall composed of sugar molecules linked with amino acids.

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Penicillin- Bacteria Killer?

• Penicillin kills bacteria by interfering with the amino acids that link the sugars together in the cell wall

• This rupturing of the wall allows water to rush in lysing the cell

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Ecology and Adaptations

• Obligate aerobes bacteria require oxygen

• Obligate anaerobes live in an oxygen free environment. - oxygen will kill them.

• Endospores are formed by some bacteria when conditions become harmful to them

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Reproductions

• Binary fission- asexual process - bacteria will simply undergo mitosis

• Sexual reproduction - Chromosomes are exchanged from one bacteria to another through the Pili

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Reproduction

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Rod shape bacteria with Pilus

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SEM of Pili

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Economic Importance

• Nitrogen fixation - all organism need nitrogen to construct things like protein, DNA, RNA and ATP.

• Nitrogen fixation - occurs in some bacteria that are able to get nitrogen from the air (N2) and convert it to NH3 or NO2, NO3

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Nitrogen Fixing nodules

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Economic Importance 2

• Bacteria cause organic material to decay. This allows for the recycling of nutrients.

• Some bacteria use fermentation which makes a variety of molecules with distinctive flavors and aromas- Yogurt, cheese, vinegar.

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Why to we culture bacteria?

• to study them in more detail

• to study or improve strains of bacteria.

• to identify which bacterium has infected you and therefore what treatment to begin.

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How Bacteria are cultured?

• Life forms require certain foods, water and temperatures to exist bacteria are no exception.

• Each type of bacteria prefers either sugars, starch, fats or proteins. So by providing a certain nutrient you will encourage a specific type of bacteria to grow.

• Temperature should be 20 C to 37 C

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Inoculation

• Adding bacteria to a culture dish is called inoculation

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Inoculation results

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Inoculation results 2

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Inoculation results 3

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Culture Results

• By Studying pure culture plates of a bacterial species, and observing the texture, aroma, color, growth pattern, height of the growth, and other physical characteristics of the colonies, you can learn a lot about the specimen.

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Testing Bacteria

• One way to determine how to treat a bacteria is to determine the type of cell wall it has.

– Thick wall usually indicate a Gram positive type

– Thin wall usually indicate a Gram negative type

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Gram Negative test

• It was found that thick wall bacteria will stain differently than those that have thin wall.

• The Gram negative test uses a process to stain bacteria.

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Gram Positive • They are usually Coccus and Bacillus in shape

• Most are harmless to people and are used for their fermentation process to make foods.

• Examples of common Gram-positive cells include Staphylococcus aureusand Streptococcus cremoris, a bacterium used in dairy production.

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Gram Negative

• These bacteria are more harmful then helpful

• Afflicted individuals are usually treated with streptomycin or erythromycin.