Bacteria & Viruses

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					Bacteria & Viruses
 Chapter 7 & Chapter 2, Section 3
 1.  coccus              12.   virus
 2. bacillus
 3. spirilium
                         13.   capsid
 4. obligate aerobes     14.   bacteriophage
 5. obligate anaerobes   15.   lytic infection
 6. facultative          16.   lysogenic
     anaerobes                 infection
 7. binary fission       17.   prophage
 8. conjugation          18.   retrovirus
 9. plasmid              19.   vaccine
 10. pathogen            20.   viroid
 11. antibiotic          21.   prion
I. Bacteria
 A.        General characteristics
      1.     Unicellular and lack a nucleus
      2.     Earliest known life forms
      3.     Size: 1-5 micrometers
B. Bacterial Structure
       DRAW Figure 2 in Chapter 7
  1.    All bacteria have an outer cell wall.
  2.   Some have a sticky slime layer around cell
       wall called a capsule.
  3.    Very simple internal organization
       Bacterial Structure
                              Cell          Ribosome
                Cell Wall   Membrane

                Flagellum       DNA
C. Classifying Bacteria
  1. Two Kingdoms
     a. Eubacteria = largest group, cell walls
        contain peptidoglycan (a carbohydrate)
     b. Archaebacteria = lack peptidoglycan, live
        in extreme environments, & their DNA
        sequences are more like eukaryotes
            c. Classification of Bacteria graphic organizer


                           are classified into the kingdoms of

       Eubacteria                                           Archaebacteria

    include a variety of                                        live in harsh
     lifestyles such as                                    environments such as

                    Infecting                             Animal
Living in                                Thick                            Salty     Hot
                      large                              digestive
   soil            organisms             mud               tracts         lakes   springs
2. Identifying Prokaryotes
  a. Shape & Arrangement
     1) Coccus (i) = spherical
        Ex: streptococci

     2) Bacillus (i) = rod shaped
        Ex: diplobacilli

     3) Spirillum (a) = spiral
D.        Optimal Growth Requirements
     1.     Warmth; 25-37 °C
     2.     Dark
     3.     Moisture
     4.     Food
     Where can we normally find these conditions?
E.        Movement
     1.     Many forms have flagella (whip-like structures) for
     2.     Some bacteria have pili which allow them to attach
            to other things.
F.        Feeding & Digestion
     1.  Autotrophic
       a. photosynthetic, ex:
       b. chemosynthetic, ex:
           deep sea thermal
     2. Heterotrophic
       a. Extracellular digestion
          1) Secrete enzymes
          2) Digest their food
          3) Absorb food back
             into their cells by
G. Circulation, Excretion and Respiration
  1. By diffusion
  2. Obligate aerobes = require a constant
     supply of oxygen in order to live
  3. Obligate anaerobes = must live in the
     absence of oxygen
  4. Facultative anaerobes = survive with or
     without oxygen
H.        Reproduction
     1.        Asexual
          a.  Binary fission - splitting into two equal cells
          b. Spore formation – for harsh conditions
             1) form spore (thick internal wall to enclose DNA)
             2) allows spore to remain dormant until
                 conditions are better for growth
2.    Sexual
     a.    Conjugation - exchange genetic information
          1) plasmids are independent circular pieces
             of DNA in bacteria
I.        Beneficial Effects
     1.    Decomposition of organic
     2.    Nitrogen fixation in some plants
           (legumes) see figure 19-7
     3.    Symbiotic relationships, ex:
           E.coli in our intestines
     4.    Used to make antibiotics
     5.    Food production: ex: yogurt,
           cheese, vinegar
     6.    Used as a tool in genetic
     7.    Bioleaching - extracting
           minerals from ore deposits
J.        Harmful Effects
     1.        Pathogenic (causes
          a.     Directly damaging cells as
                 they digest cells for food
          b.     Indirectly damaging cells
                 by releasing toxins which
                 damage hosts
          c.     Trigger body's immune
                 response, ex: fever or
          d.     Examples: botulism,
                 tuberculosis, gonorrhea,
                 typhoid fever, bubonic
                 plague, diphtheria,
                 cholera, tetanus, etc.
2.    Other problems caused by bacteria
     a.   Food spoilage (many species)
     b.   Food poisoning, ex: Salmonella
     c.   Disorders like boils, pimples, pneumonia, and
          some forms of arthritis
3. Controlling Bacteria
  a. Antibiotics
     1) Compounds that block the growth and
        reproduction of bacteria
     2) Ex: penicillin, streptomycin, tetracycline,
     3) Problems with Antibiotics
        a) Bacteria develops resistance
        b) Kills off good bacteria as well as bad
        c) Inhibits body's natural immunity
b.    Disinfectants
     1) Using chemical solutions to kill pathogens
        helps stop the spread of disease
c.    Food Storage & Processing
     1) Lowering temperature slows growth of
        bacteria, ex: refrigerator
     2) Chemical treatments such as salt or
     3) Properly canned food
          Diseases Caused By Bacteria

Disease               Pathogen                 Prevention
Tooth decay       Streptococcus mutans         Regular dental hygiene
Lyme disease      Borrelia burgdorferi         Protection from tick bites
Tetanus           Clostridium tetani           Current tetanus vaccination
Tuberculosis      Mycobacterium tuberculosis   Vaccination
Salmonella food   Salmonella enteritidis       Proper food-handling
    poisoning                                      practices
Pneumonia         Streptococcus pneumoniae     Maintaining good health
Cholera           Vibrio cholerae              Clean water supplies
II. Viruses
A. Discovery of Viruses
B. What is a Virus?
   Fig. 19-9, pg 479 with labels
C. Viral Infection
   1. Lytic Infection
   2. Lysogenic Cycle
   Fig. 19-10, pg 481 with labels
D. Retroviruses
E. Viruses vs. Living Cells
   Figure 19-11, pg 483 with labels
F. Viral Diseases
   1.   Humans
   2.   Animals
   3.   Plants
   4.   Viroids & Prions
II. Viruses
        General Characteristics
          Virus considered acellular or nonliving
          Virus lacks cytoplasm and organelles
          Virus has only a few enzymes
          Virus has only 1 type of nucleic acid (DNA or
           RNA), cells have both
          Virus never grows or carries on metabolism
          Virus does not come directly from another virus
       Viral Characteristics
           All viruses are small, only visible through
            electron microscope
           Consist of two parts:
                Nucleic acid core - can be either DNA or RNA,
                 but never both
                Outer protein coat called a “capsid”
                  Protein coat determines the shape of the virus
                  Some viruses (animal) have membraneous outer
                   envelope instead of/or on top of a protein coat
                Three basic shapes:
                  Geometric shape- e.g. Influenza or HIV
                  Spiral (helical) shaped - e.g. tobacco mosaic virus
                  Bacteriophage

                   DRAW 19-9, pg 479
                                      Tobacco Mosaic
         T4 Bacteriophage                  Virus
                            DNA                         RNA                    Virus
                                                       Capsid     Capsid


                                                                  proteins           Membrane
       Viral Infection
           Lytic Cycle
                Attachment -virus attaches itself to the receptor site of host
                   Viruses are very specific
                   In some cases, the virus is engulfed by the host cell.
                Injection -virus use enzymes to enter the cell wall of host
                 and its nucleic acid is injected into the host cell
                Replication - host’s DNA disintegrates and viral DNA or RNA
                 takes over the host cell.
                   Host cell replicates viral nucleic acids, coat proteins, and viral
                   RNA viruses (retroviruses) have special reverse transcriptase
                    enzyme to change its RNA into DNA
                Assembly - viral parts are put together to form new
                 complete viral units
                Release or lysis - new viruses release enzymes to break
                 down host’s cell wall (killing the host cell) and they are
                 released to invade other host cells
       Lysogenic Cycle (Temperate)
        Attachment - Same as lytic cycle
        Injection- Same as lytic cycle
        Splicing - the viral DNA is spliced into the
         DNA of the host
        Cellular Duplication - During normal cell
         division the viral DNA is also duplicated and
         passed on with the cell’s own DNA.
        Activation - An environmental stress
         stimulates the activation of the viral DNA
         and stages 3-5 of the lytic cycle begin.
How many of you have cold sores?
DRAW Figure 19-10, pg 481
       Harmful Effects of viruses
        Cause disease - rabies, mumps, measles,
         AIDS, chicken pox, influenza, polio,
         common cold & many more
       Beneficial Effects of viruses
        Can be used to insert desirable genetic
         information into cells
Type of Virus       Nucleic Acid   Disease
Oncogenic viruses   DNA            Cancer
Retrovirus          RNA            Cancer, AIDS
Adenoviruses        DNA            Respiratory infections
Herpesviruses       DNA            Chickenpox
Poxviruses          DNA            Smallpox

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