Viruses and Monerans

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Viruses and Monerans

• What are viruses?
• Very small particles made of nucleic acid and
  protein
• contain either DNA or RNA but not both
• nucleic acid is found inside a capsid

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• capsid is a protein shell
• nucleic acid capsid nucleocapsid
• some viruses have an envelope of lipid and
  protein surrounding nucleocapsid
• host cell - cell in which a virus or an organism
  lives

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• Viruses are all intracellular parasites
• Parasites harm hosts
• for parasite, - for host
• Parasite benefits, host is harmed

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• like a building block
• capsomere - single protein subunit of a capsid
  stacked together they form capsid

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Ebola zaire
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Classification of Viruses

• 1. Is it an RNA or DNA virus?
• 2. What is the shape of the capsid?
• 3. What is the size of the virus?
• 1 nanometer 1 billionth of a meter
• range from several nm to 300 nm

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• 4. Does the virus infect plants, animals,
  bacteria, or certain tissues in certain
  organisms?
• 5. Does the virus have an envelope?
• 6. How many capsomeres does it have?

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Bacteriophages
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Bacteriophages

• Infect bacteria
• Experiments with phages could be done fairly
  quickly and provided a lot of information about
  viruses
• viral replication - takes place inside a host
  cell
• raw materials - amino acids and nucleotides (the
  units that make up a DNA molecule)

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• Tools - ribosomes and tRNA
• Energy - provided by ATP

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Viral Replication

• Bacteriophage used as an example
• 1. Sticks to host cell - by adsorption -
  molecules on viral tail closely fit host
  molecules
• 2. Injection of viral nucleic acid
• 3. Using host material, the viral nucleic acid
  makes copies of itself and the capsid

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• 4. Assemble new viral particles
• 5. Lysis - the host cell bursts when many viral
  particles have been assembled - new particles
  infect other cells

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• this entire process is the lytic cycle - each
  cycle can yield several hundred new phages
• virulent phages - phages that cause lysis of host
  cell

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• Temperate phage - can stay inside host cells for
  a long time without causing lysis
• viral DNA incorporates itself into the host DNA
• prophage - viral DNA attached to bacterial
  chromosome
• Bacteria prophage Lysogenic bacteria

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Retroviruses

• RNA viruses
• Use RNA to make DNA (instead of using DNA to make
  RNA)
• they do it backwards - hence the name retro
  meaning backward
• HIV is a retrovirus
• responsible for certain types of cancers in
  animals and humans

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Viral transduction

• Transfer of host DNA to another organism by a
  virus
• results from temperate phage becoming virulent
• they carry sections of the host DNA to other cells

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Viroids

• infective strand of RNA
• lack capsid
• only replicate within a living cell
• infect plants

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Prions

• Infective proteins
• cause Mad Cow Disease - Bovine Spongiform
  Encephalopathy
• cause Scrapie in sheep
• causes Kuru - similar to Mad Cow

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Characteristics of Prokaryotes

• Kingdoms Archaebacteria and Eubacteria old
  kingdom Monera
• Lack a nucleus and most organelles
• have cell membrane, cell wall, ribosomes,one main
  chromosome, may have DNA plasmid(s)
• some are autotrophs, some are heterotrophs

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Kingdom Archaebacteria

• Prokaryotes
• Ancient bacteria
• Live in extreme environments
• ex hyperthermophiles - very hot temperatures
• methanogens - produce methane
• halophiles - like it salty

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Kingdom Eubacteria

• Prokaryotes
• Bacteria that are found in most environments
• Include
• beneficial bacteria
• Decomposers (saprophytes)
• nitrogen-fixing bacteria
• bacteria used in food
• oxygen producing bacteria

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Anabaena Bacillus subtilis
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E. coli Clostridium botulinum
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Shapes of bacteria

• Coccus (s) Cocci (pl) - spherical
• Bacillus (s) Bacilli(pl) - rod-shaped,
  capsule-shaped
• Spirillum (s) Spirilla (pl) - spiral, cork-screw

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Other shapes

• Coccobacilli short rods
• Square bacteria from salty pools
• Bacteria with extensions prosthecae
• Vibrio gently curved rods
• Pleomorphism- pleomorphic- variations in shape

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• Spirochetes - another group of spiral-shaped
  bacteria - one type causes syphilis

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Size of bacteria

• coccus - .5 - 1 micron
• bacillus - .5 - 20 microns
• spirillum - several microns - 500 microns

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Gleocapsa
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Cyanobacteria - blue-green bacteria

• Autotrophic
• no nucleus, few organelles
• 2 pigments
• phycocyanin - blue
• chlorophyll - green

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• May have other pigments - red, orange
• cell wall - provides support, made of amino acids
  and sugars
• binary fission - asexual reproduction copy of
  DNA made and separated cell pinches into two
  cells

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• important for food for aquatic organisms
• convert nitrogen gas to ammonia some convert
  ammonia to nitrates
• release oxygen
• sewage promotes growth

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• Oscillatoria - high count reflects polluted water
  since sewage acts as a fertilizer promoting its
  growth

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Bacteria

• Most are heterotrophic
• in every environment
• most bacteria are beneficial
• have a cell wall
• may have a capsule - outer layer which is usually
  made from sticky material so bacteria can stick
  to surfaces

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2 special groups of bacteria

• 1. Mycoplasmas - smaller than most bacteria
• dont have cell walls
• can cause lung infections

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• 2. Rickettsias - .45 microns - bacteria-like
• cant live outside of host
• can cause serious disease
• ticks and lice are vectors
• ex Lyme disease, Rocky Mountain Spotted Fever

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Nostoc
Oscillatoria - high count reflects how polluted
water since since sewage acts as a fertilizer
promoting its growth
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Oscillatoria
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Bacterial arrangements

• Diplo - in pairs - ex diplococcus
• Strepto - in chains - ex streptococcus,
  streptobacilli
• Staphylo - in clusters - ex staphylococcus

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Large spirilla
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Image Yersinia pestis Fluorescence antibody
positivity is seen as bright, intense green
staining around the bacterial cell.
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Yersinia pestis
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The Black DeathNecrosis (gangrene) of the tissue
cause by pneumonic Plague
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Bubo formed in groinInflamed lymph nodes where
the bacteria ultimately migrate
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