VIRUSES vs.

BACTERIA

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BACTERIA

VIRUSES: 20-1

BACTERIA: 20-2

• Vocabulary

– Virus

– Bacteriophage

– Capsid

– Lytic cycle

– Lysogenic cycle

– Retrovirus

• Key Concepts

– What is the difference

between a virus and a

bacteria?

– How do virus/bacteria

reproduce?

– Importance of

virus/bacteria

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– Retrovirus

– Binary fission

– Conjugation

– Obligate Anaerobe

– Obligate Aerobe

– Endospore

virus/bacteria

What is a virus?

• viruses are non-cellular particles made up of genetic material (DNA or

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made up of genetic material (DNA orRNA… not both) and protein that can invade living cells

Are Viruses Alive?• like living things,

viruses have genetic material and they can pass this on to future generations

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generations• BUT, unlike living

things, viruses are notmade of cells

• outside of a cell, they don't reproduce, feed, or grow

• Therefore, most biologists consider viruses nonliving

What do viruses do?

• viruses can invade the cells of plants, animals, and bacteria

• viruses cause illness like colds, flu’s, chicken pox, herpes, AIDS, polio, rabies,

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chicken pox, herpes, AIDS, polio, rabies, measles, mumps…

Chicken pox

What do viruses look like?• a virus is made of a core of genetic material surrounded by a protein coat (CAPSID)

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• viruses are SMALL!! (20-400 nanometers)

Bar = 100nm

• viruses come in a variety shapes: rod-shaped; tadpole-shaped; helical; cubelike (see pg 575)

T-4 bacteriophageHuman Influenza

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T-4 bacteriophageHuman Influenza

virus particles

How do viruses reproduce?

• viruses insert their genetic material into a host cell– The CAPSID (outside protein) “tricks” the cell into allowing it inside

• once inside, the viral genes take over

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• once inside, the viral genes take over

• The “hijacked” cell transcribes the viral genes– Uses the host cells own enzymes (ex: DNA Polymerase)

• one of the ways a virus takes over a cell is

described as the LYTIC CYCLE

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LYTIC CYCLE• The cells lyse (burst) when the concentration of new viral particles is high

• The lytic cycle has its name because the host cell lyses and allows viral particles to escape

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LYSOGENIC CYCLE

• Host cell is not immediately overtaken

• Viral nucleic acid is inserted into host • Viral nucleic acid is inserted into host cell’s DNA

• Host cell copies own DNA along with viral DNA

• Host cell multiples along with viral DNA

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• Each generation of daughter cells is infected with virus

• Prophage = bacteriophage’s DNA is • Prophage = bacteriophage’s DNA is imbedded host’s DNA

• Environmental trigger (e.g. heat, chemicals, etc…) activates prophage

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RETROVIRUSES:• contain RNA as their genetic material

• retroviruses infect a cell and produce a DNA copy of their RNA

– (retro = backward; RNA is copied in to DNA)

• this DNA is inserted into the host cell's DNA

• example of retroviruses:

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• example of retroviruses:

HIV

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How Can You Protect Yourself From Viral Infections?

• The best way: use of vaccines

– Preparation of weakened or killed virus or viral proteins

– When injected, the vaccine stimulates

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– When injected, the vaccine stimulates the immune system

– Sometimes produces permanent immunity

• Protect yourself

– Stay away from known sick people– Wash your hands often

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How are Bacteria Different?

• Bacteria are different in that they:

– Are much bigger– Have a different structure (made of cells) �

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– Have a different structure (made of cells) �therefore are considered “LIVING”

– Reproduce differently (asexual and sexual)

• Bacteria are prokaryotes (no nucleus)• Bacteria Have 2 Kingdoms: Archaebacteria and Eubacteria

Some bacteria you

probably familiar

with…

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The Size of Bacteria

• Prokaryotes typically range in size from 1-5um (micrometers)

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The Structure of Bacteria• 3 basic shapes: rod-shaped, spherical shaped, spiral-shaped

• they may form long chains, large clumps/clusters, or colonies

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• they may form long chains, large clumps/clusters, or colonies

• cell wall

• movement: propelled by flagella or cilia

“Breathing” (RESPIRATION) in Bacteria

• some are aerobic: respiration involves

oxygen

– obligate aerobes-cannot survive without oxygen

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– obligate aerobes-cannot survive without oxygen

• some are anaerobic: respiration without

oxygen

– obligate anaerobes-cannot survive with oxygen

How Do Bacteria Obtain Energy?

• some make their own food (like plants)= AUTOTROPHS

• some obtain their food (like us)=

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HETEROTROPHS

These bacteria eat the

nutrients in the agar.

Reproduction in Bacteria• most reproduce through binary fission (asexual) =

clones

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• Other bacteria exchange genetic information through CONJUGATION(a.k.a. bacteria sex)– A hollow bridge forms between the 2 bacterial cells and

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bacterial cells and genes move from 1 bacterium to the other

– ADVANTAGE: increases genetic diversity in the bacterial population

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•If food and space are not an issue, bacteria divide at astonishing rates!

•Some can divide every 20 minutes!!

•If this were to continue to happen, the bacteria would reach a mass of 4000x the mass of the

Earth in 48 hours!YUCK!!!

EXPONENTIAL GROWTH!!!EXPONENTIAL GROWTH!!!EXPONENTIAL GROWTH!!!EXPONENTIAL GROWTH!!!

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How Bacteria Can Be Controlled:

• sterilization: – heating/boiling OR use a disinfectant (alcohol, bleach� chemical)

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(alcohol, bleach� chemical)

• food processing: – boiling, frying, steaming, refrigeration, salt, vinegar

As labeled by

humans, there are

both “BAD” bacteria

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both “BAD” bacteria

and “GOOD”

bacteria.

• Bacteria that causes illness and disease (pathogenic)

• Bacterial diseases:

– diptheria, tuberculosis, typhoid fever, tetanus,

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– diptheria, tuberculosis, typhoid fever, tetanus, syphilis, cholera, bubonic plague

• How are the diseases caused?

– Bacteria damage the cells & tissues of an organism directly by breaking down the tissues for food

– Or… Bacteria release toxins (poisons) that travel through the organisms body

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WARNING: Disturbing

Picture!!

Ocean warning!

33Flesh-eating bacteria

•Bacteria that humans use and need in

their everyday lives.

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Escherichia coli (Esh-er-ish-e-ah coal-eye): one of many kinds of microbes that live in your gut. Wanted for helping you digest your food every day.

Lactobacillus acidophilus (lack-toe-bah-sill-us acid-off-ill-us): one of the bacteria gang wanted for turning milk into yogurt.

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Saccharomyces cerevisiae (sack-arrow-my-seas sair-uh-vis-ee-ay): a.k.a. baker's yeast. Wanted for making bread rise.

Pseudomonas putida(sue-doe-moan-us poo-tea-dah): one of many microbes wanted for cleaning wastes from sewage water at water treatment plants.

Arbuscular

Streptomyces(strep-toe-my-seas): soil bacteria wanted for making streptomycin, an antibiotic used to treat infections.

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Arbuscular mycorrhizas (ar-bus-que-ler my-kuh-rye-zuh): one of a soil-living fungus family. Wanted for helping crops take up nutrients from the soil.

Bacillus thuringiensis (bah-sill-us ther-in-gee-in-sis): a.k.a "Bt", a common soil bacterium. Wanted as a natural pest-killer in gardens and on crops.

Good Bacteria in Summary

1. Nitrogen Fixation• Most organisms

need nitrogen for DNA, RNA, proteins, and ATP

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DNA, RNA, proteins, and ATP

• Few organisms can convert nitrogen gas into useable nitrogen so they need help of legumes (beans, etc…)

2. Recycling of NutrientsExample: Decomposers

3. Foods and Medicines

4. ProducersExample: Prochlorococcus

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Example: Prochlorococcusaccounts for more ½ of primary production in open oceans

Antibiotics

How Do You Treat a Bacterial Infection?

• If prevention fails, take antibiotics• Antibiotics kill bacteria without harming the cells of humans or animals– They interfere with the cellular processes of

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– They interfere with the cellular processes of bacteria

• Many antibiotics are produced naturally by living organisms– Ex: penicillin

• Others are synthetic (man-made)