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Transcript
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