Bacteria and Viruses

Chapter 19

Bacteria

• Bacterial cells do not have nuclei so they are Prokaryotic.

• Bacteria used to be collectively grouped into the Kingdom Monera but now it is separated into 2 Kingdoms: Eubacteria and Archaebacteria.

Eubacteria

• Common bacteria, wide variety of organisms that live almost everywhere

• Some can cause disease

• Eubacteria have a cell wall that contains a carbohydrate called peptidoglycan.

Archaebacteria• Ancient bacteria that live in very

harsh environments. • Have cell walls that lack

peptidoglycan.  • In fact their DNA is more like that

of a eukaryote than a eubacteria’s.  This is why many people believe that archaebacteria are the early ancestors of eukaryotes.

Structure

• Bacteria do not have a nucleus. • Bacteria tend to be smaller than

eukaryotic cells. • Bacteria are single-celled

organisms but sometimes they stick together and live in colonies.

Structure

• Bacteria have a single circular strand of DNA.

• Bacteria reproduce by binary fission, which is basically when the cell pinches in half.

• Some bacteria have flagella that help to propel them.

Shape

• Bacilli –rod shaped

• Cocci—spherical shaped • Spirilla—spiral shaped

Cocci Bacteria

• Cocci bacteria can group together to form:– Chains—streptococci – Clusters—staphylococcus

Obtaining Energy• Bacteria can be either autotrophs or

heterotrophs.

Obtaining Energy• Bacteria can be either autotrophs or

heterotrophs.

–Autotrophs—make their own energy• photoautotroph –perform photosynthesis like plants (cyanobacteria)

• Chemoautotroph-obtain energy from inorganic materials like sulfur and ammonia

–Heterotrophs—must obtain energy from another source 

Releasing Energy• Bacteria can release energy through

cellular respiration (requires Oxygen) or fermentation (does not require Oxygen)–Obligate Aerobes—require Oxygen–Obligate Anaerobes—require Oxygen-

free conditions –Facultative Anaerobes—do not require

Oxygen but can survive in its presence

Reproduction

• Bacteria can reproduce at an incredible rate. Some will divide in as little as 20 minutes. If there were unlimited resources, bacteria could reproduce to equal 4000 times the mass of the Earth in 48 hours.

• Binary fission (assexual)

Endospore

• Some bacteria like anthrax form spores that allow them to remain dormant for months, years, even centuries. 

• This allows them to survive through extreme heat or

total lack of nutrients.

Bacteria in Nature

• Bacteria can be useful.  Many help to capture energy from the sun others breakdown dead or decaying material so that the nutrients and materials can be recycled into a form that other organisms can use.

Human Uses

• Food processing

• Digest oil spills • Synthesize drugs and

chemicals

Bacteria and Disease• Bacteria cause disease in 2

ways:

–Destroy the hosts tissues (Tb)

–Release toxins that poison the host (C. botulism)

• See chart p. 486/489

Antibiotics• Antibiotics are used to block

the growth and reproduction of bacteria.

• Why are some bacteria drug resistant?

Controlling Bacteria

• Sterilization—is the process of destroying the bacteria on a nonliving surface by extreme heat or chemicals.

• What is the difference between an antiseptic and a disinfectant?

STOP

Viruses

• Viruses are particles of nucleic acid (either DNA or RNA) surrounded by a protein coat (called a capsid). 

• Viruses vary in size and structure.

• Viruses can only replicate by entering a host cell and using that cell’s materials to copy itself.

Viral Infection• When a virus enters a cell it will

begin one of 2 cycles: p 481– Lytic Cycle—virus enters a cell,

copies itself, and bursts the cell – Lysogenic Cycle—virus enters a

cell, embeds its DNA into the cell’s DNA so that it is replicated along with the host cell, eventually this virus will wake up and begin destroying the cells. 

HIV

• Human Immunodeficiency Virus—The virus that causes AIDS

• HIV attaches to and enters macrophages ( a type of white blood cell). It then uses an enzyme called reverse transcriptase to change its RNA into DNA.  This process causes many mistakes (mutations).  This is why HIV mutates or changes so easily.  This new DNA is embedded in the host cell’s DNA.  When the virus replicates it does not burst the cell, instead the new viruses are released by budding.  A person with HIV usually shows no symptoms of the disease for at least 8-10 years. 

HIV

• Eventually the HIV virus begins to invade T cells.  When the virus replicates in the T cells it burst and destroys them.  It is the low number of T cells that leave the body unable to protect itself against infection thus the onset of AIDS. 

http://learn.genetics.utah.edu/content/begin/cells/scale/

Emerging Viruses

• 1.      West Nile

• 2.      Avian Flu

• 3.      Hanta Virus

Prions

• Prions are disease-causing proteins with no nucleic acid.

• These proteins are folded into shapes that prevent them from working.

• Contact with a prion will cause a protein in your body to become folded incorrectly and not function.

• Mad Cow disease or Creutzfeldt-Jakob Disease is caused by prions. 

• Prions cannot be destroyed by cooking

Bacteria…

Single Cell Organism

This type of infection is treated with antibiotics

Can be harmful or beneficial to humans

Capable of multiplying by themselves

Meningitis

Pneumonia

Strep Throat

Staph Infection

All of these photos are of different types of bacteria. Many bacteria have cilia and/or flagellum for locomotion. These are single celled organisms

Rigid Cell Wall

Viruses…Viruses are not considered living organisms because they do not have the ability to reproduce on their own. They must have a host cell to reproduce. Viruses are very simple and contain either DNA or RNA.

Non-living

Has a protein

coat

Must have a host to

reproduceHIV

Flu

Chicken Pox

Common Cold

Viruses differ from bacteria in that all viruses — A cause insect-borne diseasesB can be destroyed by antibioticsC have rigid cell wallsD must be reproduced in living cells

D

Which of the following is found in both cells and viruses? A SilicaB Genetic materialC Digestive cavityD Flagella

B

Some antibiotics cause patients to exhibit digestive side effects. These side effects are most often the result of — A bacteria being killed in the digestive tractB the antibiotics being converted into stomach acidsC too much water being drawn into the digestive tractD the stomach wall being torn

A

Which of the following explains why antibiotics can treat flu-like symptoms caused by bacteria but are ineffective against flu? A Flu is a response to an antigen.B Antibiotics require time to work.C Antibiotics strengthen antibodies.D Flu is caused by a virus.

D

Lactose is a naturally occurring sugar found in milk. Some dairy products, such as yogurt, may contain live bacteria. These products are useful to people who lack the ability to digest lactose. What does this information demonstrate?

A Bacteria raise the acidity of processed foods.B Some bacteria interfere with digestion.C Bacteria can prevent insulin production.D Some bacteria are beneficial to human health.

D