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Name _______________________________________________________________________ Test Date _Fri, 3/30___
UNIT 11 - MICROBIOLOGY
I. VIRUSES (pg 478-483)
 Living or non-living?
o Lack a _cell membrane______
o Do not contain _enzymes____ for _metabolism_
o Lack _ribosomes____ for protein synthesis
o Do contain _genetic material_____
o _Reproduce_____, although they require a _host____ cell
 Typically referred to as a _particle____ or _virion__.
A. Structure of Viruses
The following structures are found in all viruses:
 Genetic Material – The genome of a virus may be either _DNA___ or _RNA___, but never both. It can be _singlestranded____ or _double-stranded__, _circular___ or _linear__.
 Protein Coat – The DNA or RNA is surrounded by a protein coat called a capsid. The proteins making up the capsid are
known as _capsomeres_____ and play an important role in the _pathogenicity________ of the virus. In addition, the capsid
has _carbohydrate___ ID tags known as _glycoproteins____ which can _mutate____ to enable the virus to escape
detection by a host cell’s immune system.
The following additional structures may be present:
 Viral Envelope – Many viruses have an outer membrane known as an envelope. A viral particle “steals” the components for
its envelope from the host cell membrane, so a viral envelope is primarily composed of _phospholipids___. It aids in the
attachment of the virus to the host cell, but a virus enclosed by an envelope is also more sensitive to _drying___.
Examples of viruses with envelopes are _HIV, flu virus, cold virus_________.
 Tail Fibers – Viruses that infect _bacteria_____ are known as _bacteriophages____. They have “tail fibers” to aid in
attachment.
B. Host Range
The host range of a virus is the range of host cells that it can infect. It is based on a complementary fit between viral
_glycoproteins____ and receptor _proteins___ on the host cell membrane.
 Some viruses have broad host ranges which can include several species; for example, swine flu and rabies
 Some viruses have narrow host ranges where they infect only a single species; for example, the
_bacteriophage___________________ that attacks E. coli.
 Some viruses only infect a particular type of tissue or cell within a single species; for example the human cold virus infects only
cells of the _upper respiratory tract______; HIV binds to receptors on certain _white blood cells_____.
C. Viral Replication
A virus can infect a host cell and use it for reproduction in two ways:
 Lytic Infection – _Symptomatic____ cycle in which virus _destroys_____ host cell DNA. Examples are _cold, flu, rabies,
measles, etc … most viruses!_______
 Lysogenic Infection – _Asymptomatic________ cycle in which viral DNA is incorporated into _host cell DNA_______.
Examples are _HIV, chicken pox virus_____.
There are two initial steps that are common to all types of viral infections:
1) Virus attaches to _cell membrane_____ of _host ____ cell.
2) Virus releases _genetic material__________ into cell, either by _entering cell, typically through endocytosis____
cell or _injecting___ genetic material into it.
_Lytic__ Cycle
…………………………………………………………………………………………………………………………………………………
_Lysogenic____ Cycle
D. Viruses and Disease (485-490, 503, 504, 539, 688, 690-692)
All viruses are _parasites_____, meaning they require a living host and they cause harm to that host.
1. Herpesvirus – Group of viruses that are _ubiquitous__ and have many forms. Results in lifelong infections, although
virus can move back and forth from _lytic___ to _lysogenic__ cycle. Group includes viruses that cause cold sores,
chicken pox, genital warts, shingles, and mononucleosis.
2. HIV - _Human Immunodeficiency Virus____ – Affects _white__ blood cells and immune system. The HIV virus is a
_retrovirus_____. Retroviruses contain _RNA__ and the enzyme, _reverse transcriptase__ which allows the viral RNA to be
_reverse-transcribed____ into _DNA___. Initial symptoms are flu-like, then virus enters _lysogenic____ cycle and replicates
in lymph nodes, sometimes for years. When the HIV virus becomes active, it causes _AIDS____ - Acquired ImmunoDeficiency
Syndrome. Death of the patient results from _secondary infections; breakdown of immune system_______.
3. Human Papilloma Virus – Diverse group of DNA viruses; common cause of skin warts. Danger comes from group of sexuallytransmitted HPV which can cause genital warts, but more seriously, _cervical cancer_____. Controversial
_vaccine_____ has been produced; effective against most types of sexually-transmitted HPV.
4. Other viral diseases – hepatitis, influenza, smallpox, measles, common cold, rabies, Ebola
II. BACTERIA
(pp. 471 - 477)
Bacteria make up two kingdoms, the _Archaebacteria___ and _Eubacteria___. In this unit, we will focus on the
kingdom that has the greater impact on our lives, the _Eubacteria____.
 _Prokaryotic________
 _Unicellular______
 Cell Structures
o Cell wall composed of _peptidoglycan___.
 _Eubacteria only_____
o _DNA ______
 _Single, circular chromosome__________
 Found in region known as _nucleoid______
o _Cell membrane_________
o _Ribosomes_____________
o _Cytosol________________
o Most bacteria are motile and have one or more _flagella_____.
o May have hair-like appendages called _pili__ that allow bacteria to _adhere_ to surfaces or other _bacteria_____.
o Some bacteria have an outer _capsule_______; helps bacterial cells attach to a substrate or deter the
host’s infection-fighting cells.
A. Classification
1. Gram Stain Reaction - Eubacteria are organized into two groups based on differences in the amount of _peptidoglycan____
in their cell walls. This difference can be seen by performing a _Gram stain_______. Gram-positive bacteria have a
_greater__ concentration of peptidoglycan and appear _purple______ under the microscope. Gram-negative
bacteria have more complex cell walls with _less___ peptidoglycan – they appear _reddish__________.
Gram-_negative____ bacteria are generally more resistant to _antibiotics____.
2. Shape – Bacteria are also grouped according to their shape. There are three major shapes:
_________________ _________________
________________
B. Reproduction & Adaptations
1. Binary Fission - _Asexual_____ reproduction in which the bacteria doubles its DNA, grows 2X its size, and then
splits in half. Produces _two identical__ bacterial cells.
2. Adaptations for Genetic Variation
 Conjugation – a form of “sexual reproduction”. Involves direct transfer of a _plasmid___ from one bacteria to another
via _pili____. A plasmid is a small, self-replicating piece of DNA separate from the main chromosome.
 Transformation – Direct uptake of DNA from surroundings
 Transduction – Use of viral _vector_______ to incorporate new genetic information into bacterial genome. Often used
in biotechnology as a means of having bacteria produce human proteins.
3. Adaptations for Survival
 Endospores - Some bacteria are able to produce _endospores__________ to survive adverse conditions. A hard,
protective wall forms around the DNA of the bacteria; can survive for centuries. When favorable conditions return, the
spores revive and germinate. Examples include Bacillus anthracis; Clostridium botulinum
 Toxin Production – Some _pathogenic_____ bacteria are able to secrete a poison known as a _toxin______. For
example, Clostridium botulinum produces a neurotoxin that causes a very serious type of food poisoning known as
_botulism______ characterized by a spreading _paralysis______. This powerful toxin has important uses in medicine
and is also used in _cosmetic surgery____ procedures.
C. Bacterial Diseases – tuberculosis, Lyme’s disease, scarlet fever, rheumatic fever, whooping cough, tetanus, gangrene, leprosy,
Syphilis, diphtheria, anthrax, Bubonic plague, cholera
D. Benefits of Bacteria
1. _Decomposers___ - recycle nutrients
2. _Nitrogen Fixation_____ – All organisms require nitrogen for making _proteins___ and _nucleic acids____
but they cannot use N2 gas from atmosphere. Bacteria convert nitrogen to a form plants can absorb.
3. Food Processing – Most bacteria can carry out _fermentation____ in _anaerobic____ conditions. This is
used to produce _cheeses, yogurt, pickles, etc____________________________________________
4. _Mutualistic__ Inhabitants of our Digestive Tract – They help us with _digestion_____ and
produce _vitamins___.
III. OTHER IMPORTANT MICROORGANISMS
 Protists
o Giardia
o Plasmodium
 Fungi
o Ringworm/Athlete’s Foot
 Animals

o Hookworm, tapeworm, Ascaris
Prions