Bacteria and Viruses Chapter 19. Bacteria & Viruses.

Bacteria and Viruses

Chapter 19

Bacteria & Viruses

19.1 Bacteria

Come in many shapes and sizes

Most common microorganisms are prokaryotes

Average size of 1-5 micrometers– Compared to eukaryotic cells that are 10-100

micrometers in diameter

2 Branches of Bacteria (Domains)

Archebacteria (similar to early Earth)– Confined to extreme environments – Methanogens - reduce CO2 to CH4

– Extreme halophiles - salt loving– Thermoacidophiles– Similar to early earth– More closely related to eukaryotes than to

modern bacteria Eubacteria (most modern)

– very diverse

Bacterial Classification

Prokaryotic Phylogeny

Prokaryotic & Eukaryotic Cells

Classifying Prokaryotes

Eubacteria– Largest prokaryote Domain– Lack nuclei– Cell wall of a carbohydrate- Peptidoglycan– Cell membrane around cytoplasm– Some have an extra cell wall on the outside to resist

damage

Classifying Prokaryotes

Archaebacteria– Lack nuclei– Have cell walls without

peptidoglycan– Are chemically different

from Eubacteria– Many live in extremely

harsh environments

Bacteria Shapes

Identifying Prokaryotes

Shapes– Bacilli- Rod shaped– Cocci- Spherical shaped– Sprilla- spiral shaped

Colorized SEM 9,000 Colorized SEM 12,000

Identifying Prokaryotes

Cell walls– Gram staining used to tell them apart

– Gram+ bacteria look purple

– Gram- bacteria look pink

The Bacterial Cell Wall

Instead of cellulose, contain peptidoglycan– A polymer of modified sugars cross-linked

with amino acids The gram stain distinguishes many

disease causing bacteria based on the type of cell wall

Many antibiotics work by attacking the bacterial cell wall

Gram (+) Purple– accept gram stain– have simpler cell walls with large amounts of

peptidoglycan Gram (-) Pink

– do not stain– have more complex cell walls with less

peptidoglycan– cell walls contain lipopolysaccharides– are more likely to be pathogenic (cause disease)– more resistant to antibiotics

The Gram Stain

Cell Wall & Gram Stain

Gram (+) & Gram (-)

Gram (+)Purple & Gram (-)Pink

Identifying Prokaryotes

Movement– Flagella

– Lash, snake or spiral forward

– They do not move at all

About half are capable of directional movement.

3 mechanisms:– flagella - different from eukaryotes– spiral shaped bacteria (spirochetes) have a

filament that spirals around the cell under the outer sheath

– some bacteria secrete slimy chemicals & glide Taxis

– movement toward or away from a stimulus– many bacteria exhibit this form of movement

Motility (movement)

Structures of Movement

Structure of Prokaryotic Flagella

Metabolic Diversity

Heterotrophs– Chemoheterotrophs: must take in organic molecules

for energy and carbon

– Photoheterotrophs: Use sunlight for energy but need organic compounds for a carbon source

Metabolic Diversity

Autotrophs– Chemoautotrophs: perform chemosynthesis to

make carbon from carbon dioxide. Does not require sunlight

– Photoautotrophs: use light to convert carbon dioxide and water into carbon compounds and oxygen gas.

Getting Energy

Bacteria need a constant supply of energy

Obligate aerobes- require constant supply of oxygen

Obligate anaerobes- need no oxygen, for some oxygen will kill it

Facultative anaerobes- survive with or with out oxygen

Growth and Reproduction

Binary fission (to split)

Conjugation

Spore formation

Binary Fission

Bacterial Conjugation

Some bacteria form resistant cells called endospores (11,000 year old spores found)

Resist extremes of temperature, pH, etc.

Endospores (example: Anthrax)

Importance of Bacteria

Only a minority cause disease Many are essential to life on earth Decomposers

– Break down dead matter Nitrogen Fixers

– Converts nitrogen into a form plants can use Humans use Bacteria Often live in symbiotic relationships with other

organisms

19.2 Viruses

What is a virus?– Particles of nucleic acid and proteins

– Core made up of DNA or RNA surrounded by a capsid

– Need to infect a

living host to reproduce

Head

Tail

Tail fiber

DNA

300,

000

Viral Structure

Bacteriophage

Are Viruses Alive?

Viruses contain nucleic acids & proteins Viruses, by themselves, cannot make or use

food, grow or reproduce Some scientists believe viruses were never

independently living organisms Others believe viruses evolved from simple

bacteria like mycoplasmas & rickettsiae Another hypothesis: viruses are genes that have

escaped from the genomes of living cells Not much evidence to support any one of these

Viral Infection

Lytic Cycle– Virus attaches to host cell– Injects its DNA– Host makes RNA from viral DNA– Cell begins to make copies of virus– New viruses form– Host cell bursts

Lytic Cycle of the T4 Phage

Viral Infection

Lysogenic Cycle– Virus attaches to host cell– Injects DNA– Viral DNA incorporates itself into the host DNA– Viral DNA can be dormant– Once it becomes active, it follows the 4 processes in

the lytic cycle

Lytic and Lysogenic Cycle (video)

http://www.youtube.com/watch?v=gU8XeqI7yts&feature=related

Phage Lytic and Lysogenic Cycles

Viral Infection

Retrovirus: Genetic information is RNA

– Produces DNA copy and creates a prophage

– Example:

HIV/AIDS

Envelope

Glycoprotein

Protein coat

RNA (two identical strands)

Reverse transcriptase

19.3 Diseases Caused by Bacteria and Viruses

Pathogens- disease causing agents

Bacterial Disease

Viral Diseases

Diseases Caused By Bacteria

How does bacteria produce disease?

– Damage the cells and tissues by breaking down the cells for food

– Releasing toxins (poisons into the body)

Preventing Diseases

Vaccines

Immunity

Antibiotics

Controlling Bacteria

Sterilization

Disinfectants

Proper food storage

Diseases Caused by Viruses

Viruses disrupt the body’s normal equilibrium

Cannot be treated with antibiotics

Viruses can infect humans and plants

Virus-like Particles (Viroids)

Viroids- single stranded RNA molecule with no capsid– They cause diseases in plants

– Infect cell and produce more viroids by disrupting the plant metabolism

Virus-like Particles (Prions)

Prions- contain only protein; no DNA or RNA– They cause diseases in animals and humans

– Prions clump and cause normal protein to clump with it- creating new prions

Prion Action

Chapter 19Viruses and Bacteria

Multiple Choice Practice Questions

19–1

–Which characteristic distinguishes eubacteria from archaebacteria? Eubacteria lack peptidoglycan in their cell walls. Eubacteria contain peptidoglycan in their cell walls. Eubacteria lack a nucleus. Eubacteria do not possess mitochondria.

19–1

–Which characteristic distinguishes eubacteria from archaebacteria? Eubacteria lack peptidoglycan in their cell walls. Eubacteria contain peptidoglycan in their cell walls. Eubacteria lack a nucleus. Eubacteria do not possess mitochondria.

19–1

– Rod-shaped prokaryotes are called bacilli. cocci. spirilla. streptococci.

19–1

– Rod-shaped prokaryotes are called bacilli. cocci. spirilla. streptococci.

19–1

– Bacteria that must live without oxygen are called obligate aerobes. facultative anaerobes. obligate anaerobes. facultative aerobes.

19–1

– Bacteria that must live without oxygen are called obligate aerobes. facultative anaerobes. obligate anaerobes. facultative aerobes.

19–1

– Prokaryotes that make their own food molecules from carbon dioxide and water but live where there is no light are called

photoautotrophs. photoheterotrophs. chemoautotrophs. chemoheterotrophs.

19–1

– Prokaryotes that make their own food molecules from carbon dioxide and water but live where there is no light are called

photoautotrophs. photoheterotrophs. chemoautotrophs. chemoheterotrophs.

19–1

– Bacteria that attack and digest the tissue of dead organisms are called

decomposers. nitrogen fixers. chemoautotrophs. archaebacteria.

19–1

– Bacteria that attack and digest the tissue of dead organisms are called

decomposers. nitrogen fixers. chemoautotrophs. archaebacteria.

19–2

– Viruses that contain RNA as their genetic information are known as

prions. oncoviruses. retroviruses. bacteriophage.

19–2

– Viruses that contain RNA as their genetic information are known as

prions. oncoviruses. retroviruses. bacteriophage.

19–2

– The first type of virus to be studied was the bacteriophage. tobacco mosaic virus. influenza virus. AIDS virus.

19–2

– The first type of virus to be studied was the bacteriophage. tobacco mosaic virus. influenza virus. AIDS virus.

19–2–Which of the following statements about viruses is true? Viruses appear similar to bacteria when studied with a light

microscope. Viruses display the essential characteristics of living things.

Viruses can reproduce independently if they contain DNA.

Viruses cannot reproduce unless they infect a living cell.

19–2–Which of the following statements about viruses is true? Viruses appear similar to bacteria when studied with a light

microscope. Viruses display the essential characteristics of living things.

Viruses can reproduce independently if they contain DNA.

Viruses cannot reproduce unless they infect a living cell.

19–2

– A virus integrates its DNA into the DNA of the host cell but remains inactive for a while in

a lytic infection. a lysogenic infection. neither a lytic nor a lysogenic infection. retroviral infection.

19–2

– A virus integrates its DNA into the DNA of the host cell but remains inactive for a while in

a lytic infection. a lysogenic infection. neither a lytic nor a lysogenic infection. retroviral infection.

19–2

– Retroviruses are considered unique because they have RNA in their capsid and not DNA. they have DNA in their capsid and not RNA. after infection of a host cell, their RNA makes DNA. after infection of a host cell, their DNA makes RNA.

19–2

– Retroviruses are considered unique because they have RNA in their capsid and not DNA. they have DNA in their capsid and not RNA. after infection of a host cell, their RNA makes DNA. after infection of a host cell, their DNA makes RNA.

19–3–Biologists know that bacteria can cause human disease by

entering cells and using the cell to make new bacteria. producing toxic substances that interfere with normal cell functi decomposing the remains of dead organisms. changing atmospheric nitrogen into nitrogen compounds.

19–3–Biologists know that bacteria can cause human disease by

entering cells and using the cell to make new bacteria. producing toxic substances that interfere with normal cell functio decomposing the remains of dead organisms. changing atmospheric nitrogen into nitrogen compounds.

19–3

– A process that destroys bacteria by subjecting them to great heat is known as

refrigeration. sterilization. pickling. boiling.

19–3

– A process that destroys bacteria by subjecting them to great heat is known as

refrigeration. sterilization. pickling. boiling.

19–3

– Which of the following diseases is transmitted by a mosquito bite?

influenza measles West Nile virus chickenpox

19–3

– Which of the following diseases is transmitted by a mosquito bite?

influenza measles West Nile virus chickenpox

19–3

– Which of the following diseases is thought to be caused by prions?

diphtheria mad cow disease tuberculosis smallpox

19–3

– Which of the following diseases is thought to be caused by prions?

diphtheria mad cow disease tuberculosis smallpox

19–3

– The best way to combat viral diseases is to use antibiotics. to treat individual symptoms. to use preventive vaccines. to let the disease “cure itself.”

19–3

– The best way to combat viral diseases is to use antibiotics. to treat individual symptoms. to use preventive vaccines. to let the disease “cure itself.”