Chapters 19,20,21

Start @ Chapter 19

Virus and Bacteria

Microbiology

Viruses… The Living Dead?

• Living because…– Reproduce–Has DNA/RNA “Blueprint of Life”– Evolves

• Non-living because…– Require a host (Parasitic)– To reproduce, they use the host– It does not have cells

Sizes

• Most are so small they can’t be seen with normal microscopes– Require Electron microscopes

• Are smaller than Monerans (Bacteria)

Viral Shapes

• Spirals, Polygons, rods, bullets, needles

• Bacteriophages

Viral Parts• Capsid: outer protein coat– Allows the virus to enter a cell– “Tricks” the cell

• Genetic Material: DNA or RNA

• Envelope: Protective layer around the capsid.–NOT ALL VIRUSES HAVE THESE– Comes from the host cell membrane

Other facts about Viruses

• Almost all organisms have at least one virus that infects them

• They are “host-specific”– Usually only infect one species

Types of Viruses

• Bacteriophages

• DNA Viruses

• RNA Viruses

• Retroviruses

Bacteriophages

• Infect Bacteria Only

DNA Viruses

• Have DNA as their genetic material

Single-stranded DNA virus:

Canine Parvovirus

Double-stranded DNA virus:

Chicken pox (Varicella zoster)

DNA Viruses

Herpes Virus in a host cell

Human Papilloma virus: causes warts

Adenovirus: causes some colds

RNA Viruses• Has RNA as genetic

material

Rhinovirus: Common Cold

Paramyxovirus: Measles and Mumps (in a host cell)

Rabies virus

Retroviruses

• RNA as genetic material

• To replicate, they convert the RNA back into DNA and use host to make more RNA

HIV (Human immunodeficiency virus)

How Viruses Infect

• Two ways it can happen

• Lytic Infection

• Lysogenic Infection

Lytic Infection (The Outlaw)

• Simple Version: Virus enters a cell, replicates, and bursts the cell

1. Landing: Virus lands on Cell

2. Injection: Virus injects DNA into Cell

3. Replicate: Cell makes RNA out of Virus’s DNA, and shuts down Cell

4. Assemble: Cell then puts together the virus components

5. Burst: So many viruses are created that the cell lyses, or bursts.

Lysogenic Infection

• Virus DNA is made indefinitely by the cell

• Virus places its DNA into the host’s DNA so when replication happens it copies both the virus and the host

• Prophage:Viral DNA in the Host DNA

• Eventually will become Lytic

Drawing/Picture

Bacteria

• Prokaryotes: unicellular organisms that lack a nucleus– Bacteria

• Prokaryotes are now classified as Monerans (Kingdom: Monera)

• Divided into two groups: Eubacteria and Archaebacteria

Eubacteria• Larger of the two kingdoms (in both

size and variety)

• Live almost everywhere

• Surrounded by a cell wall– Cell wall contains peptidoglycan

• Other parts: Cell membrane & cytoplasm

Archaebacteria• Same structure, different chemically

• They lack peptidoglycan and have different membrane lipids

• DNA sequence is more closely related to eukaryotes than eubacteria

Archaebacteria

• Live in extreme conditions• Examples:–Methanogens: Produce methane gas• Live in stomachs and thick mud

– Salty conditions– Boiling water– Sulfur pits– Etc…

Ways to Identify a Prokaryote

• Shape

• Chemical Components of Cell Wall

• Movement

• Way they get Energy

Shapes

• Coccus: Round bacteria• Example: Staphylococcus sp.

Shapes

• Bacillus: rod bacteria– Example: Bacillus anthracis

Shapes

• Spirochetes: spiral bacteria– Example: Treponema pallidum

Cell Walls and Gram Staining

• Two different types are found in eubacteria

• We can pick them out using a method called Gram Staining – (We will do this if we get something to

grow!)

Gram Staining Steps• Two dyes: violet and red (counterstain)

• Violet: Applied first– Stains peptidoglycan in the cell wall

• Wash with alcohol– If color stays: Gram Positive– If color washes away: Gram Negative

• Red is then applied to make Gram Negative visible with pink color

Movement

• No movement

• Flagella: Whip-like structure

• Lash

• Snake

• Spiral

• Glide

Ways to Obtain Energy• Two main groups

• We have already talked about!

• Heterotrophs: Energy by consuming others/organic molecules

• Autotrophs: Make their own food

Bacterial Heterotrophs

• Chemoheterotrophs: Obtain energy solely from organic molecules–Most animals are this kind too!

• Photoheterotrophs: Photosynthetic, get energy from the sun but need others to get their carbon from

Bacterial Autotrophs

• Photoautotrophs: Carryout photosyntehsis– Require light source– Ex: Cyanobacteria: chlorophyll a

• Chemoautotrophs: Carryout Chemosynthesis– Do not require light

Getting that Release

• Obligate aerobes: Requires oxygen– Ex: Mycobacterium tuberculosis• Causes Tuberculosis

• Obligate anaerobes: Do not require oxygen– Ex: Clostridium botulinum• Soil bacteria that can work its way into food

if not properly sterilized!

Special Release• Facultative anaerobes– Facultative: Function in different ways

• Can switch between living in oxygen or not (respiration or fermentation)

• Means they could live practically everywhere

• Ex: E. coli: Large intestine to sewage

Bacterial Reproduction (3 way)

• Binary Fission: – Doubles in size, replicates DNA and

divides in half.

• Conjugation: – Exchange of DNA between bacteria– Hollow tube connects bacteria– Responsible for genetic diversity

Spore Formation

• Occurs when environment is unfavorable

• Endospore: thick internal wall that sections off the DNA with cytoplasm

• Spores can last until the conditions are acceptable to grow in

• Ex: Bacillus antracis: Anthrax

Importance of Bacteria

• Producers that produce energy

• Decomposers:– If materials did not cycle in the

environment, life would not exist

– Sewage treatment: Turns trash into purified water, carbon dioxide, nitrogen, and fertilizers

Nitrogen fixers

• We’ve discussed this with the nitrogen cycle but lets see what we remember

• What do we need nitrogen for?• What is the process takes it from air?

• Symbiotic: Rhizobium and legumes

Human Uses

• Bacteria is in food and beverages– Ex: Yogurt, Dairy products, Vinegar, Sausage,

Pickles, anything that ferments (usually)

• Oil spills: Certain ones digest petroleum

• Our Digestion: E. coli: Makes a number of vitamins that we cannot produce

The Medical World

• Genetic Engineering

• Bacillus thuringiensis–Main ingredient in Bt-Corn– Genetically engineered from soil

bacteria to be placed into corn DNA– Kills insects by releases a toxin that

affects insects and causes their stomachs to burst.

Only a few bad eggs…

• Most bacteria and viruses don’t harm

• The ones that do are called PATHOGENS– Disease-causing agents

• Disease: result of pathogen infecting the host

What do microorganisms need?

• Each species has an OPTIMUM– Temperature– pH– Air– Osmotic Pressure–Water– Nutrients

How can we prevent them from getting these requirements?

• Heat (sterilize)• Change pH• Add salt or sugar • Remove oxygen (canning)• Remove water by

Dehydrating foods

How do we spread diseases and how do we stop them?

• Five methods for spreading disease.– AIR– FOOD–WATER– PERSON to PERSON– VECTORS- insects

How does an infection makes us sick?

• What they do: Grow and Reproduce– Destroys cells– Release toxins– Block passages

• What we do: – Crummy Article

Germ Theory of Disease 1857

Louis Pasteur• Eliminates theory of spontaneous

generation• Saves the wine Industry in France• Proposes that there is a relationship

between a microorganism (pathogen) and a disease

• Develops– Pasteurization– Vaccines for anthrax and rabies

Koch’s Postulates 1876

Find suspect organism

Isolate suspect and grow in pure culture

Inject pure culture into healthy subject and get the same disease symptoms

Re-isolate the same suspect organism and grow it in pure culture

Vaccines:

• Treatment for viruses

• Taken as a preventative method

• Cannot help you once you have the disease

• Viruses can become resistant to these, but it is not usually a fast process

• Human production

Antibiotics:

• Treatment for bacterial infections

• Taken once you have the disease

• Cannot be used as a preventative

• Bacteria can easily become resistant to these

• Bacteria and some fungi produce these

Vaccines

• Involves your immune system being stimulated

• Dead or weakened antigen (foreign particle)• Engulfing cells and antibody producing cells

destroy the antigen• Memory cells prepare for another infection– Response to virus is faster and stronger the

second time

• Adds to the health of the community

Antibiotics

• Work ONLY on bacteria– Bacteria are prokaryotic, we are eukaryotic– Bacteria have a cell wall, we do not.

• These help, but our immune system still has to “clean-up”

• Examples:– Penicillin – stops cell wall

formation– Tetracycline – stops protein synthesis– Ciprofloxacin – stops DNA replication

Proper use of antibioticsPrevents Resistance

Only taking them for bacterial infections

Taking pills on time

Taking all your prescription

Concentration of Bacteria at which you feel better =====

Time in DaysShot of Penicillin- Pill taking intervals – missed interval

Concentration of antibiotic -

Effective concentration of antibiotic ---

Concentration of bacteria ……C

on

cen

trati

on

Antibiotic Resistance

• Development of Resistance– Alter the antibiotic– Alter the target or structure– Pump out the antibiotic

• Developing new anti-resistance antibiotics– Target the mechanism that confers resistance

• Stop alteration of antibiotic• Stop alteration of target• Stop the molecular pumping mechanism

Stop the Spread of antibiotic resistance

Do not demand antibiotics

Take them exactly as prescribed

Wash fruits and vegetables(no such thing) thoroughly; avoid raw eggs and undercooked meat, especially in ground form

Use soaps and other products with antibacterial chemicals only when protecting a sick person whose defenses are weakened

Viroids

• Single-stranded RNA molecules that have no capsids

• Infect host, produces more viroids

• Disrupts metabolism, resulting in smaller growth of plant

Prions

• Tiny virus-like particles like contain only proteins usually found in the brain

• Scrapie• Kuru• Mad cow disease

The BIG picture

• Diet• Rest• Exercise both aerobic and resistance

• Personal Cleanliness e.g. wash your hands

• Proper Preparation and storage of food– It Must Have Been Something You Ate

• Environmental Cleanliness pollution, filth

• Annual Physical

Big Picture cont…

• Report symptoms promptly to a responsible person

• Follow physicians instructions– antibiotics

• Vaccinations: Vital– The Vaccine Conundrum