Bacteria and Viruses

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Chapter 19

• Bacteria and Viruses

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Prokaryotes single-celled organisms that lack a
nucleus

• Eubacteria
• walls contain peptidoglycan (a carbohydrate found
  in cell walls of eubacteria)
• Archaebacteria includes methanogens, halophiles
  and thermophiles
• Lack peptidoglycan
• DNA sequences of key archaebacteria genes are
  more like eukaryotes than eubacteria.

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Classifying prokaryotes

• Done by shape
• Reaction to Gram stain (due to nature of cell
  wall)
• Arrangement
• Diplo 2 Staphylo cluster Strepto chain
• Movement
• Some non-motile
• Some undulate like a snake
• Others use flagella or secretions to move

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• Identifying Prokaryotes
• 1. Shapes
• a. Bacilli (rod shaped)
• b. Cocci (spherical)
• c. Spirilla (spiral)

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• Reaction to Gram stain is due to nature of cell
  walls
• a. Gram-positive
• (cell walls contain w/peptidoglycan)
  appear purple
• b. Gram-negative
• (cell walls lack
• peptidoglycan
• appear red

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Obtaining Energy

• 1. Autotrophs
• a. Photoautotrophs obtain energy from
  photosynthesis
• b. Chemoautotrophs obtain energy from
  inorganic molecules
• 2. Heterotrophs
• a. Can cause food poisoning
• b. Photoheterotrophs
• photosynthetic,
• but also need organic compounds for
  nutrition

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Releasing Energy

• 1. Obligate aerobes require oxygen
• 2. Obligate anaerobes cannot live in
  presence of oxygen
• 3. Facultative anaerobes do not need
  oxygen, but can live in the presence of it

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Growth and Reproduction

• 1. Binary fission cell divides, asexual
• 2. Conjugation transfer of genetic
  information from one cell to another, sexual
• 3. In unfavorable conditions, many
  bacteria can form endospores can remain
  dormant for months or years

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Exponential Growth Curve
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• Uses of Bacteria
• Food cheese, yogurt, buttermilk, sour cream,
  pickles, sauerkraut
• Industry cleaning up oil spills, mining
  minerals, synthesizing drugs (such as insulin and
  human growth hormone)

• Assist in digestion symbiotic relationship in
  our digestive tract.

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Bacteria in Nature

• Decomposers
• 1. Help recycle nutrients break down dead
  organisms
• 2. Used in sewage treatment

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Bacteria are important as decomposers

• Recycles important nutrients.

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Bacteria in the Nitrogen Cycle

• Nitrification fixing N2
• 1. Nitrogen fixation converting nitrogen gas
  into nitrate or ammonia
• 2. Example Rhizoacter which grow on roots of
  soybeans and other legumes. Reduces need for
  application of fertilizer.
• Bacteria also release nitrogen
• back into the environment.

Called (denitrification)
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• Controlling Bacteria
• 1. Sterilization destroy bacteria by
  subjecting them to great heat or chemicals
• a. Boiling, frying, steaming can all
  kill bacteria
• b. Disinfectant chemical solutions can
  be used in homes and hospitals
• 2. Refrigeration bacteria grow slowly at
  low temperatures

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Bacteria and Disease

• 1. Pathogen disease-causing agents
• 2. 2 ways bacteria cause disease
• a. Break down tissues for food
• b. Release toxins
• 3. Many can be prevented with vaccines,
  can be treated with antibiotics

Cross-linkages holding cell wall and cell
membrane together do not form properly.
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Antibiotics

• First discovered accidentally, Alexander Fleming
• Work by interfering with cell wall production so
  bacterial cant reproduce.
• Cross linkages cannot form so cell wall develops
  holes and bacterium ruptures.
• Some bacteria have antibiotic properties ex
  Streptomyces
• Only bacteria not viruses can be killed with
  antibiotic treatment.

Bacterium elongates preparing to divide.
Then ruptures when cell wall fails.
PENICILLIN KILLING E. coli
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Bacteria in Biotechnology

• Transformation Bacterial cells pick up DNA from
  other sources (including dead bacteria) and
  incorporate it into their own genome. Increases
  genetic variety and opportunities for resistance.
• Transduction Process of using a virus to
  transfer DNA from one bacterial cell to another.
• PCR insert gene into bacterial plasmid for
  rapid replication of sample

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Bacterial DiseasesNecrotizing fasciitis

• Caused by a mutated Streptococcus
• Reproduces rapidly
• Tissue must be removed to stop spread
• Patient is put into a pressure chamber (forcing
  O2 into tissue to assist healing) to reduce the
  spread.

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Anthrax

• Direct contact
• Many different strains
• Found in lower vertebrates goats, sheep, cattle
• Three types
• Cutaneous skin death rare if treated
• Inhalation Cold-like fatal
• Gastrointestinal 25-60

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Bubonic Plague or Black Death

• Caused by pathogenic bacteria spread from China
  on trade ships (13
• Symptoms include swollen lymph nodes (buboes,
  hence the name), high fever, and delirium.
• 90 death rate
• Killed 1/3 of the population of Europe within a 5
  year period 1347-1352 (including Shakespeares
  siblings)

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Lyme Disease

• Transmitted by Deer tick.

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Lyme Disease Symptoms
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Botulism E. Coli

• Botulism
• Muscle-paralyzing disease.
• Food-borne
• Anaerobic
• E. Coli
• 1,000 of strains
• Undercooked meat
• Sewage water
• Lives in intestines without causing a problem

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VIRUSES

• Non-living particles consisting of nucleic acid
  (RNA or DNA) surrounded by a protein coat
• No organelles, no nucleus, etc.
• Parasitic
• Rely on a host for replication
• Bacteriophage virus that
• infects bacteria

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III. Viruses

• Viruses particles of nucleic acid and protein
• 1. Nucleic acid DNA or RNA that
  contains instructions for making new copies of
  the virus
• 2. Capsid outer protein coat

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Bacteriophage virus that infect bacteria

• Mechanism
• Fibers attach
• Contractile sheath squeezes down
• Nucleic acid (DNA or RNA) in head (capsid) is
  injected into bacterial host

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In a viral infection, do people get sick from the
protein coat or the DNA core?
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Viral Infection Cycles

• 2 types of viral infections
• a. Lytic infection virus enters cell, make
  copies of itself and causes the cell to burst
• b. Lysogenic infection virus embeds its
  DNA into DNA of host and is replicated
  with host cells DNA

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Virus ReproductionThe Lysogenic Cycle
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Virus ReproductionThe Lytic Cycle
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Viral Diseases

• 1. Common human diseases caused by a virus
• common cold (rhinovirus), chickenpox, measles,
  mumps, polio, rabies, hepatitis
• Many viruses can be prevented through the use of
  vaccines (polio, measles, influenza)
• 2. Oncogenic viruses cause cancer
• 3. Retroviruses contain RNA
• 4. Prions contain no DNA or RNA, only protein

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Human Viral Diseases Ebola

• Found in Primates
• Animal-Borne Virus
• RNA virus
• Incubation 2-21 days
• Fever, headache, joint muscle pain rash red
  eyes
• Extensive bleeding from all orifices.

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SARSSevere Acute Respiratory Syndrome
Hot Zone- China, Toronto Symptoms Flu like-
fever, headache, dry cough Transmission- Person
to person contact, respiratory secretion Military
action has been taken to keep virus controlled.
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Small Pox

• Humans are the natural host.
• Spread by face to face contact. Also body
  fluids.
• Most Contagious during Early Rash continues till
  the last scab falls off.

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HIVHuman Immune Deficiency Virus

• Fastest Spreading disease in Africa
• Effects white blood cells. T-Cells
• AIDS diagnosed when T-cell count falls below 200

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West Nile Virus

• Host Birds
• Spread through mosquitoes
• Fever, headache, and body aches, occasionally
  with skin rash and swollen lymph nodes.
• Rare encephalitis
• 1 of mosquitos carry the virus, 1 of those
  infected will die.

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Viroids and prions

• Viroids tiny, naked circular RNA that infect
  plants do not code for proteins, but use
  cellular enzymes to reproduce stunt plant growth
• Prions infectious proteins mad cow
  disease trigger chain reaction conversions a
  transmissible protein