Bacteria and Viruses

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Bacteria and Viruses

• Biology
• Chapter 19
• Pgs. 470 - 495

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19-1 Bacteria
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Bacteria

• Prokaryotes
• Smallest and most common microorganism
• Lack a nucleus

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Classifying Prokaryotes

• Until recently all prokaryotes wer placed in the
  kingdom Monera
• 2 different groups
• Eubacteria
• Archaebacteria

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Eubacteria

• Some are heterotrophs
• Live anywhere except the extreme environments
• Some are parasites and get nutrients from living
  organisms
• Some are saprophytes and feed on dead organisms
  (saprobe)
• Some are autotrophs and are photosynthetic
• Cyanobacteria, or blue-green algae
• Some are chemosynthetic autotrophs
• Break down and release energy from inorganic
  compounds containing sulfur and nitrogen

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Archaebacteria

• Live in extremely harsh environments
• 3 major types based on where they live
• Methanogens
• Lives in oxygen-free environments and produce
  methane gas
• Found in digestive tract of cows, and in sewage
  plants
• Thermacidophiles
• Lives in areas of hot acidic water with sulfur
• Found in cracks deep in the ocean at volcanic
  vents
• Extreme Halophiles
• Lives only in water with high concentrations of
  salt
• Found in the Great Salt Lake and Dead Sea

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Identifying Prokaryotes

• Prokaryotes are identified by characteristics
  such as shape, the chemical nature of their cell
  walls, the way they move, and the way they obtain
  energy

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Structure of bacteria

• Prokaryotic cells that have small ribosomes
• Genes are located on a single circular chromosome
• Contain a cell wall

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Identification Prokaryotes

• Shape of bacteria
• Circular, rod-shaped, spiral shaped
• Gram staining
• A chemical that stains certain cell walls based
  on its chemical composition
• Bacteria that are gram positive will stain purple
  and gram negative are pink
• Helps scientist know which antibiotic to use to
  destroy the cell wall
• Patterns of growth
• (diplo-) paired, (staphylo-) resemble grapes, and
  (strepto-) chain

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Shapes of Bacteria
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Patterns of Growth
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Metabolic Diversity

• Heterotrophs
• Autotrophs
• Photoautotrophs use light energy to convert
  carbon dioxide and water into food
• Chemoautotrophs use energy from chemical
  reactions to convert carbon dioxide and water
  into food

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Adaptations in bacteria

• Obligate aerobes
• Bacteria that require oxygen
• Example Mycobacterium tuberculosis
  (tuberculosis)
• Obligate anaerobes
• Bacteria that are killed by oxygen
• Example Clostridium botulinum (botulism)
• Facultative anaerobes
• Do not require oxygen but are not killed in the
  presence of oxygen
• Example E. coli

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Reproduction of bacteria

• Binary fission
• The bacteria copy its DNA and grow and split into
  two cells
• Some can reproduce every 20 minutes
• Conjugation
• Is when one bacterium transfers all or part of
  its chromosome into another cell through or on a
  structure called a pili
• the receiving cell can now do binary fission and
  make new cells

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• Endospores
• Produced by bacteria when conditions are
  unfavorable
• Carries the DNA and a little cytoplasm in a tough
  outer covering
• Do not reproduce
• When conditions improve the endospore germinates
  and produces a bacterial cell

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Important of Bacteria

• Bacteria help fertilize fields and return
  nutrients to the soil
• Nitrogen fixing
• The process in which bacteria convert N2 to
  ammonia
• Other bacteria convert ammonia into nitrite and
  nitrate, which plants use
• Some nitrogen fixing bacteria live symbiotically
  with the roots of trees and legumes in a swollen
  area called nodules

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Important bacteria

• Decompose organic materials and returning these
  materials to the environment
• Used to make some foods
• yogurt, Swiss cheese, and pickles
• Some produce antibiotics that we use medically to
  fight off other types of infectious bacteria

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19-2 Viruses
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What is a virus?

• Virus is from the Latin word poison
• A non-living infectious particle
• Do not exhibit all the criteria for life
• Do not respirate, grow, or develop
• A typical virus is composed of a core of DNA or
  RNA surrounded by a protein coat.

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• Host cell - the cell that a virus infects and
  uses to replicate
• Viruses infect only certain types of cells
• Capsid an outer coat of protein
• Enable a virus to enter a host cell
• Bacteriophages viruses that infect bacteria

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Viral Structure

• Core of the virus contains the DNA or RNA
• Specific proteins on the coat determine the type
  of cells a virus can infect
• To infect a cell the virus must be able to bind
  to the outside of the cell
• Contain a specific attachment protein

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Viral Infection

• 2 major types
• Lytic infection
• In a lytic infection, a virus enters a cell, make
  copies of itself, and causes the cell to burst.
• Lysogenic infection
• In a lysogenic infection, a virus integrates its
  DNA into the DNA of the host cell, and the viral
  genetic information replicates along with the
  host cells DNA.

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• Lytic Cycle (steps)
• Attachment of virus to the cell membrane
• Injection of viral DNA or RNA into the cell
• Virus forces the cell machinery to make new viral
  DNA and viral proteins
• The new viruses are assembled and fill the cell
• The cell becomes so full it ruptures, releasing
  new viruses
• http//student.ccbcmd.edu/immt/PLP/lyticCycle/

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• Lysogenic cycle (steps)
• Attachment of the virus to the cell membrane
• Injection of the viral DNA or RNA into the cell
• Viral DNA becomes integrated into the host cells
  chromosomes (now call prophage)
• Each time the cell replicates, it also passes
  along a copy of the provirus
• At some point there is a signal to enter the
  lytic cycle
• The provirus leaves the host chromosome and
  starts the lytic cycle
• Virus that cause herpes simplex I and II,
  hepatitis B, chicken pox virus, and HIV all use
  the lysogenic cycle

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Retroviruses

• Retrovirus
• Has RNA at its core
• It injects the RNA along with an enzyme (reverse
  transcriptase) into the host cell
• The enzyme reads the RNA and makes complementary
  DNA
• The double stranded DNA that is formed becomes a
  provirus and integrates into the host DNA

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Viruses and Living Cells

• Viruses must infect a living cell in order to
  grow and reproduce
• Viruses are considered a parasite

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193 Diseases Caused by Bacteria and Viruses
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Bacterial Disease in Humans

• Pathogens a disease-causing agent
• About half of human diseases are caused by
  bacteria
• Bacteria produce disease in one of two general
  ways.
• Some bacteria damage the cells and tissues of the
  infected organism directly by breaking down the
  cells for food.
• Other bacteria release toxins that travel
  throughout the body interfering with the normal
  activity of the host.

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Preventing Bacterial Diseases

• Vaccine
• A preparation of weakened or killed pathogens
• Stimulates the bodys immune system to produce an
  immunity to the disease
• Immunity the bodys ability to destroy new
  pathogens
• Antibiotics
• Compounds that block the growth and reproduction
  of bacteria
• Penicillin interfere with the bacterias ability
  to build cell walls

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Controlling Bacteria

• There are various methods used to control
  bacterial growth, including sterilization,
  disinfectants, and food processing.

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Viral Disease in Humans

• Like bacteria, viruses produce disease by
  disrupting the bodys normal equilibrium.
• Named after the disease they cause, or the
  organism they infect
• Adenovirus infects the adenoids
• (common cold)

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Types of viruses

• Tumor virus
• Convert or transform normal cells into cancer
  cells
• Examples are
• papillomavirus (causes warts)
• hepatitis B
• Plant viruses
• Can change the color of the flowers of plants
  such as tulips, gladioli and pansies
• First virus identified was the tobacco mosaic
  virus