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Chapter 16Chapter 16Bacteria and VirusesBacteria and Viruses
ProkaryotesProkaryotes
Or 100 Trillion Friends ThatOr 100 Trillion Friends That You Didn’t Know You HadYou Didn’t Know You Had
Bacteria
• Were once included in Kingdom Monera (which doesn’t exist anymore)
• Now 2 separate groups:
–Archeabacteria
–Eubacteria
Archaebacteria—cell wall lacks peptidoglycan--contains membrane lipids (fats) not found in any other living things.
--Live in extremely harsh environments Ex.-Oxygen-free locations (thick mud, digestive tract of animals, Great Salt Lake, hot springs, etc)
Biologists refer to Archeaebacteria as “extremophiles” (Lovers of the extremes)
Thermophiles: Heat lovers; live in hot springs of Yellowstone National Park or deep sea ocean vents
Halophiles: Salt lovers; thrive in areas like Great Salt Lake
Methanogens: Oxygen free environments; such as mud at bottom of lakes and swamps where they produce “swamp gas” (methane)
Eubacteria—usually surrounded by a cellwall (made of peptidoglycan—a carbohydrate)that protects the cell from injury and determines its shape
--As a result (of the protective cell wall), these bacteria can live almost anywhere. (fresh water, salt water, on land, on or in human body, etc)
E. coli, a Typical Eubacterium
DNA
PiliFlagellum
Bacilli: rod-shaped prok’s
Cocci: Spherical prok’s
Spirilla: Spiral and corkscrew-shaped prok’s
Prokaryotes are identified by:
1. SHAPE
2.Cell Walls
TwoTwo different kinds in Eubacteria.•Completely composed of peptidoglycan (thick) •Less peptidoglycan and an additional outer membrane (thin)
How can you tell the difference??Gram Staining: Test with violet and pink dyes.
Under a microscope, if the bacteria is purplepurple they are Gram-Positive;Gram-Positive; This is because of extra thick cell wall (lots of peptidoglycan) If bacteria is pinkpink it is Gram-negativeGram-negative.. (not a lot of peptidoglycan)
Gram Staining Procedure
How is Gram Staining Useful?
• Doctors use Gram staining to identify bacteria in order to prescribe the correct antibiotics. Some antibiotics only work against Gram-Gram-positive bacteriapositive bacteria.
3. Movement
Some move, some don’t (non-motile)
If they do move, how do they move?
-flagella (might be scattered all over the cell, or in one area)-pili (short projections that help bacteria stick to each other and to surfaces)-“spiral” or “snake” forward-glide a slime like material they secrete
Metabolic DiversityWays bacteria obtain energy!
(modes of nutrition) Chemoheterotrophs-must take in organic molecules for both energy and supply of carbon
Photoheterotroph-perform photosynthesis forenergy, but must take in organic compoundsas a carbon source
Photoautotrophs-use light energy to convertCO2 and H2O to carbon compounds and O2
Chemoautotrophs-make organic carbon molecules from CO2 (don’t require light)
Growth and Reproduction- Bacteria will divide very quickly if their environment is favorable
- Binary Fission: Asexual reproductionAsexual reproduction
- offspring are genetically identical to parent - no new genetic combinations - under ideal conditions can occur every 20 min
- creates large numbers of bacteria in a short time
http://www.youtube.com/watch?v=5Xi2Nc1UicQJeff Simmonds - The Multiplication Song
• Each spot represents Each spot represents
a single bacteriala single bacterial
cell that reproduced cell that reproduced
by binary fission toby binary fission to
produce millions ofproduce millions of
genetically identicalgenetically identical
cells.cells.
• Genetically identical,Genetically identical,
good or bad?good or bad?
Exchanging Genetic InformationExchanging Genetic Information• Bacterial cells need to be able to exchange genetic Bacterial cells need to be able to exchange genetic
information information
- creates new genetic combinations which increases the ability - creates new genetic combinations which increases the ability of the bacteria to surviveof the bacteria to survive
• Bacteria have 3 methods for exchanging DNABacteria have 3 methods for exchanging DNA
-Transduction-Transduction – viruses carry DNA from one bacterial – viruses carry DNA from one bacterial cell cell to anotherto another
-Transformation-Transformation – bacteria can absorb – bacteria can absorb ““nakednaked”” DNA DNA released by dead bacteria from released by dead bacteria from the the environmentenvironment
- - ConjugationConjugation – two bacteria join at a conjugation – two bacteria join at a conjugation bridge, bridge, one bacteria passes on a one bacteria passes on a copy of its plasmid or copy of its plasmid or
chromosomechromosome
Exchanging Genetic InformationExchanging Genetic Information
TransductionTransduction – – DNA is carried from one DNA is carried from one bacteria to another by a virusbacteria to another by a virus
Transformation: Bacteria absorb Transformation: Bacteria absorb ““nakednaked”” DNA from the DNA from the
environmentenvironment
ConjugationConjugation
Conjugation- Conjugation- one cell passes a copy of one cell passes a copy of its plasmid or chromosome to anotherits plasmid or chromosome to another
Donor CellRecipient Cell
A special pilus formsa connection calleda conjugation bridgebetween 2 bacterialcells
Plasmid Conjugation bridge
The donor cell copies its plasmidor chromosome andpasses the copy through the conjugation bridge
Cells separate
Why are Bacteria important?
–Bacteria are vital to the living world. • Some are producers that capture energy by photosynthesis.
• Others are decomposers that break down the nutrients in dead matter.
• Still other bacteria have human uses.
Human Uses of Bacteria
–foods and beverages–removal of waste and poisons from water
–mining minerals from the ground–synthesis of drugs and chemicals via genetic engineering
–production of vitamins in human intestines
Viruses (Cell Pirates)• Virus: a piece of hereditary material
covered by protein that infects and reproduces only inside a living organism
• doesn’t grow, respond, or eat
• some can be made into crystals and be dormant for years
Virus Structures
RNA
Lytic Cycle
Viral Infection
2.Lysogenic Infection: virus integrates its DNA into the DNA of host & viral genetic info replicates along with host cell’s DNA
- Can remain inactive for long time
Prophage: viral DNA that is embedded in host’s DNA
-eventually, viral DNA will be activated & new viruses will be made
Lysogenic Cycle
• Simply put, both types of viruses follow the same path in different time frames:
1. The virus attaches to the cell
2. The virus invades the cell
3. The virus makes copies of its DNA
4. Then the new viruses are released
Section 19-3Diseases caused by Bacteria
and Viruses
• Pathogens: disease causing agents.
Bacteria produce disease in one of two ways:
1. Damage the cells and tissues of the infected organism directly by breaking down the cells for food.
2. Release toxins (poisons) that travel throughout the body interfering with the normal activity of the host.
Bacterial Disease in Humans
Lyme Disease Strep Throat
Bullseye mark around bite
How do we stop thesetypes of infections?
Antibiotics – Compounds that block the growth and reproduction of bacteria; not effective against viruses.
There are various methods used to control bacterial growth, including:
• Sterilization – Destroys all bacteria by subjecting them to great heat for a period of time. (Autoclave)
• Disinfectants – Chemical solutions that kill pathogenic bacteria. (household cleaners)
•Food Storage and Processing • Refrigerate food because the bacteria will take longer to multiply.
• Boiling, frying, or steaming can sterilize certain foods.
Viral Disease in Humans–Viruses can attack and destroy certain
cells in the body, causing symptoms of the disease.
PREVENTION
Vaccine – Is a preparation of weakened or killed pathogens. It works by prompting the body to produce immunity to the disease.
Most vaccines work only if used before an infection begins.
Viral Diseases in Humans
• Chicken pox
Chickenpox Smallpox
