Viruses and Bacteria

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Viruses and Bacteria

• Chapter 18

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Remember the requirements of living things

• Made of Cells
• Reproduce
• Use energy, Grow and Develop
• Homeostasis
• Heredity/Pass of Traits
• Adapt to Environment/Evolve
• Interdependence

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Not Alive?

• Not made of cells
• Segment of nucleic acid in a protein coat
• No respiration, growth and development

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• Viruses Latin for poison
• Very small
• Cause disease pathogens
• Infect cell and use it to reproduce
• Discovered in 1835

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• Variety of shapes

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Naming Viruses

• 1. After disease they cause
• Rabies viruses
• Poliovirus
• 2. After organ or tissue they infect
• Adenovirus adenoids
• 3. Most now have genus ending in virus
• 4. Code numbers for similar viruses
• Escherichia coli has T1 to T7 (T type)
• 5. If infects bacteria bacteriophage or phage

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Structure

• Protein coat (capsid) may contain RNA or DNA but
  not both
• RNA AIDS, Flu, Rabies
• DNA Warts, Chickenpox, Mononucleosis
• May have a membrane (envelope) surrounding capsid
  to help it enter cells

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Attachment is Specific

• Virus must attach before it can infect
• Protein coat of virus attaches to protein on host
  cells surface
• Attachment protein for each virus is very
  specific
• Polio virus only infects intestine and nerve
  cells
• Smallpox only infects humans

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Viral Reproduction

• Have to use host cells for replication
• May enter plant cells through points of injury
  and animals by endocytosis

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Lytic Cycle

• Viral infection, replication and cell destruction

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Lysogenic Cycle

• No new viruses made
• Provirus viral gene inserted in host chromosome
  with copies made when cell divides
• Change in environment may cause lytic cycle to
  start

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Symptoms of Proviruses

• Because lysogenic in reproduction it can remain
  in cells until a flare up
• Herpes simplex I coldsores
• Herpes Simplex II genital herpes
• Hepatitis B hepatitis B
• Chicken Pox virus can later cause shingles
  (painful infection of some nerve cells)

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Retroviruses

• Only have RNA, no DNA
• Makes DNA from RNA using reverse transcriptase it
  carries
• DNA placed into host DNA and becomes provirus
• If person has reverse transcriptase in them it
  means they have been infected with a retrovirus
• HIV

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How HIV Infects Cells

• Attachment
• Virus surface studded with glycoproteins
• Fits human cell receptor CD4
• Humans have CD4 on immune system cells called
  lymphocytes and macrophages

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• Entry into Macrophages
• Matches both the CD4 and CCR5 so can enter
• Lymphocytes do not have CCR5 so cant enter until
  later

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• Replication
• Inside the capsid comes apart and releases RNA
• Reverse transcriptase in virus makes a DNA
  version of the RNA (lots of mistakes so lots of
  mutations)
• Viral DNA inserts into host DNA and makes copies
  of itself
• New viruses bud out without killing cell

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• AIDS
• Continues to replicate and mutate for years
• Eventually recognize glycoprotein on lymphocyte
  called T cells
• T cells are destroyed
• T cells are important in immune system, without
  them you cant fight off other diseases
• Spread through semen or vaginal fluid not casual
  contact

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Other Viral Diseases

• Influenza Flu Virus
• Upper respiratory infection
• 1918 1919 22 million Americans and Europeans
  die
• 36,000 per year estimate now

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• Cancer
• Hepatitis B liver cancer
• Epstein-Barr Burkitts lymphoma
• Human Papilloma Virus cervical cancer

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• Smallpox
• variola virus
• Humans only natural host
• Prolonged face-to-face contact, bodily fluids,
  air in enclosed spaces, contaminated objects
• Fever, red spots on tongue, rash to bumps that
  have a belly button look to feeling like BB
  pellets under skin
• 30 die survivors may go blind and have scars
• Vaccines led to eradication
• Last natural case 1977
• Lab acquired case 1978

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Emerging Diseases

• 1999 West Nile Virus
• Spread by mosquito
• mild flu-like symptoms
• In elderly possible inflammation of brain

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• Hanta Virus
• Southwest United States
• 38 death rate

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Prions and Viroids

• Prion
• Folded proteins but no nucleic acids
• Mad Cow Disease
• Creutzfeldt-Jakob Disease
• Viroids
• Single strand of RNA with no capsid
• Hepatitis D

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18.2 Archaebacteria and Eubacteria

• Prokaryotes
• No Internal Compartmentalization no nucleus or
  organelles
• Cell size generally smaller
• All are single celled
• Single circular strand of DNA
• Reproduce by binary fission
• Simpler flagella than eukaryotes
• More metabolic diversity can survive without
  oxygen

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Structure Reproduction of Bacteria

• Cell wall keeps it from bursting
• May Reproduce by Binary Fission
• Simple asexual reproduction by dividing in two
• May happen every 20 minutes
• May Reproduce by Conjugation
• Form of sexual reproduction where 1 bacterium
  transfers all or some of its genetic material to
  another
• New genetic combination

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Bacterial Cell Shapes

• Bacillus - rod
• Coccus - round
• Spirillum - spiral

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• Strepto form strands
• Staphylo - clusters

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• Strep Throat
• group A streptococcus
• Initial symptoms
• Fever, stomach pain, and red, swollen tonsils
• Other symptoms after 3 days
• Red and white patches in throat, difficulty
  swallowing, headache
• Rapid test
• If positive 10-days antibiotics
• If untreated more sever sickness may occur

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• Gram-staining dye reacts with cell wall
• Gram positive or Gram negative

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• Antibiotics interfere with life processes of
  bacteria

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Chapter 19 Protists

• Protist
• Uni- or multicellular
• Microscopic or very large
• Heterotrophic or autotrophic
• All Eukaryotes have membrane bound organelles
• Can cause diseases like malaria or sleeping
  sickness

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Protozoa 19.1

• Animal-like so heterotrophs
• All unicellular

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Protozoa Amoebas

• Use pseudopodia for movement and feeding
• No cell wall
• Asexual Reproduction

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Protozoa Flagellates

• Have one or more flagella
• Harmful and beneficial
• African sleeping sickness
• Termite symbiosis

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Protozoa Ciliates

• Use cilia to move
• Asexual or like conjugation
• Paramecium

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Protozoa Sporozoans

• Most reproduce using spores
• Reproductive cells develop without fertilization
• All are parasites
• Malaria

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Algae 19.2

• Plant-like autotrophs using photosynthesis
• No roots, stems, or leaves
• Unicellular (a.k.a. phytoplankton) or
  multicellular

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Fungus-like Protists 19.3

• Decompose organisms
• Can move and contain no chitin in cell wall