Bio11 Notes Virus PDF

What is a Virus?  Definition of a Virus non-cellular, infectious particles approximately 20 to 400 nm in size made of nucleic acids, proteins, and in some cases, lipids  Viruses vs. Cells Characteristics Virus...

What is a Virus?  Definition of a Virus non-cellular, infectious particles approximately 20 to 400 nm in size made of nucleic acids, proteins, and in some cases, lipids  Viruses vs. Cells Characteristics Virus -DNA or RNA core, plus Cell Structure cytoplasm, nucleus, capsid Reproduction -only within host cell -sexually or asexually Genetic code -DNA or RNA -DNA Growth & development -no -yes Obtain and use energy -no -yes Respond to environment -no -yes Change (evolve) over time -yes -yes  Viral Structure – Animal Nucleic acid core – made of either DNA or RNA Capsid – a protective protein coat surrounding the core Antigens – proteins that identify and bind to receptors of the host cell’s membrane Envelope membrane – an outer layer that fuses with the host cell’s membrane during infection  Viral Structure – Bacteriophage Bacteriophages (“bacteria eaters”) are viruses that infect bacteria and destroy them. They have 2 regions: Tail tail sheath tail fibres Head capsid DNA core  Viral Structure – Plant e.g. Tobacco Mosaic Virus (TMV) causes tobacco leaves to develop a pattern of spots called a mosaic Simple structure: RNA core Capsid proteins Immunization Types of Immunization  Active Immunization (artificial) Active immunization is the injection of a vaccine – a weakened form of a pathogen the immune system creates antibodies against the pathogen and develops a “memory” e.g. measles vaccine  Passive Immunization (artificial) Passive immunization is the injection of antibodies (Immunoglobulins) so that the body does not need to produce them itself lasts for only a short period of time because they are eventually broken down e.g. rabies antibodies (Ig) after an animal bite  Herd Immunization Herd immunization occurs Herd Immunity Thresholds when enough individuals (HITs): Measles 92-95% have been vaccinated so Pertussis 92-94% that the non-vaccinated Diphtheria and Rubella 83- 86% individuals are also Smallpox and Polio 80-86% protected Mumps 75-86% SARS 50-80% Ebola 33-60% Influenza 33-44% When None of the Population Gets Immunized When Only Some of the Population Gets Immunized When a Large Percentage of the Population Gets Immunized Immune System  Immune System Defences 1st Line of Defence: 3rd Line of Defence: skin barrier B cells mucous membranes plasma cells mucus/saliva/tears memory B cells sweat antibodies 2nd Line of Defence: helper T cells inflammatory response killer T cells phagocytic white blood cells fever interferon Viral Infection  HIV Infection Stages: 1) Attachment 2) Entry 3) Replication 4) Biosynthesis 5) Assembly 6) Release Lytic and Lysogenic Life Cycles of Bacteriophages  Lytic Infection Lytic infection – destroys (lyses) infected cell Stages: 1) Attachment and Injection 2) Circularization of viral DNA 3) Biosynthesis and Assembly 4) Lyses of host cell  Lysogenic Infection Lysogenic infection – viral DNA integrates within host DNA Stages: *1-2) Lytic stages 3) Integration of viral DNA 4) Reproduction of host cell 5) Exit of viral DNA Viral Transmission  Viral Transmission Viral transmission – The passing of viruses from one individual to another: 1) Direct physical contact 2) Indirect physical contact 3) Droplet contact 4) Airborne transmission 5) Fecal-oral transmission 6) Vector transmission  Direct Physical Contact touching an infected individual, including sexual contact e.g. HIV (Human Immunodeficiency Virus)  Indirect Physical Contact usually by touching a contaminated surface (fomite) e.g. Norwalk virus  Droplet Contact coughing or sneezing on another individual e.g. SARS (Severe Acute Respiratory Syndrome)  Airborne Transmission the virus can remain in the air for long periods e.g. Influenza (flu)  Fecal-Oral Transmission usually from unwashed hands, contaminated food or water sources due to lack of sanitation and hygiene e.g. Hepatitis A  Vector Transmission animal that carries and transmits a virus to another animal e.g. West Nile Virus Pandemics  Definition of Pandemic Pandemics are outbreaks of infectious disease that spread across a large region and sometimes even the entire world. 20ᵗʰ Century Flu Pandemics Spanish Flu Pandemic (1918-1919) H1N1 Pandemic (2009)  Introduction to Kingdom Monera  Kingdom Monera Kingdom Monera – all members are single-celled and lack a nucleus (prokaryote) collectively known as the “bacteria”  Characteristics of Monerans Characteristics Description Kingdom -Monera Domains -two: Eubacteria & Archaebacteria Size -1 to 10 µm Cell organization -unicellular Nucleus -absent Genetic material -nucleoid + plasmid Organelles -none (but has many ribosomes) Cell Wall -present (Gram + or Gram -) Structures of a Typical Moneran Cell  Classification of Bacteria In the three domain system of classification, there are two separate groups of bacteria: 1) Eubacteria 2) Archaebacteria  Eubacteria vs. Archaebacteria Eubacteria Archaebacteria known as “true bacteria” known as “ancient live in most environments bacteria” or discovered before “extremophiles” archaebacteria live in harsh environments cell wall made of discovered in 1977 by Carl peptidoglycan Woese cell wall made without peptidoglycan  Eubacteria Types 1. Proteobacteria 2) Gram-positives 3) Cyanobacteria 4) Spirochetes 5) Chlamydia  1) Proteobacteria Proteobacteria – a major group of Gram-negatives including several pathogens E. coli  2) Gram-positives Gram-positives – a diverse group of bacteria that are more receptive to antibiotics than gram- negatives due to the absence of an outer membrane Clostridium tetani (tetanus)  3) Cyanobacteria Cyanobacteria – obtain their energy through photosynthesis blue-green colour can cause harmful “algal blooms” Nostoc  4) Spirochetes Spirochetes – long, corkscrew-shaped bacteria cause diseases such as Lyme Disease from ticks and Syphilis (an STD) Treponema pallidum (Syphilis)  5) Chlamydia Chlamydia – disease causing bacteria that are obligate intracellular parasites causes the STD “Chlamydia” Chlamydia trachomatis  Archaebacteria Types 1) Methanogens 2) Halophiles 3) Thermophiles  1) Methanogens Methanogens – live in oxygen-free environments, producing methane gas as a by- product e.g. in thick mud, digestive system of animals, etc.  2) Halophiles Halophiles – live in extremely salty environments e.g. in the Dead Sea  3) Thermophiles Thermophiles – live in extremely high temperature environments e.g. in hot springs Identification of Bacteria  Identification of Cells Bacteria can be identified in several ways: 1) Cell shape 2) Cell organization 3) Cell wall 4) Motility 5) Nutrition and energy requirement 6) Oxygen requirement 7) Reproduction 8) Colony morphology  1) Cell Shape Bacteria cells come in three basic shapes: 1) Bacilli – rod shaped 2) Cocci – spherical shaped 3) Spirilla – spiral shaped 2a) Cell Organization – Cocci 2b) Cell Organization – Bacilli 2c) Cell Organization – Spirilla, etc.  3a) Cell Wall – “Gram-positive” “Gram-positive” – cell wall made of a thick peptidoglycan layer  3b) Cell Wall – “Gram-negative” “Gram-negative” – cell wall made of a thin peptidoglycan layer and a second outer membrane  4) Motility Motility – movement in bacteria can be achieved by several methods: swarming swimming twitching gliding sliding  5) Nutrition and Energy Requirement Mode of Nutrition Energy Source Carbon Source Autotroph Photoautotroph Light CO₂ Chemoautotroph Inorganic chemicals CO₂ Heterotroph Photoheterotroph Light Organic compounds Chemoheterotroph Organic compounds Organic compounds  6) Oxygen Requirement Obligate aerobes – requires a constant supply of O₂ (e.g. Mycobacterium tuberculosis) Obligate anaerobes – must live in the absence of O₂ (e.g. Clostridium botulinum) Facultative anaerobes – can live with or without O₂ (e.g. E. coli) Aerotolerant anaerobes – tolerates O₂ but doesn’t require it (e.g. Lactobacillus)  7a) Reproduction – Binary Fission Binary fission – a form of asexual reproduction in which a bacterium divides equally to produce two identical daughter cells  7b) Reproduction – Conjugation Conjugation – the transfer of genetic material between two bacteria through a sex pilus 7c) Reproduction – Endospore Formation Endospore – a type of dormant spore that develops during unfavourable growing conditions  8) Colony Morphology Colony morphology – the characteristics of a bacterial colony grown on agar in a Petri dish (e.g. shape, edge, surface, elevation) Diversity of Bacteria Ecological Roles and Human Uses of Bacteria Ecological Roles 1) Saprophytic bacteria 2) Sewage treatment 3) Nitrogen fixation 4) Symbiotic bacteria of the digestive tract Human Uses 1) Food production 2) Biodegradation 3) Genetic Engineering 4) Bioleaching Ecological Role #1: “Saprophytic Bacteria” Saprophytic bacteria – recycle nutrients in the environment by decomposing dead organic material Ecological Role #2: “Sewage Treatment” Sewage treatment – bacteria added to waste water breaks down complex compounds in human waste, discarded food and waste chemicals  Ecological Role #3: “Nitrogen Fixation” Nitrogen fixation – symbiotic Rhizobium bacteria living in the root nodules of some plants fix atmospheric nitrogen gas (N₂) into ammonia (NH₃) Ecological Role #4: “Symbiotic Bacteria of the Digestive Tract” Symbiotic bacteria of the digestive tract – help with digestion in the intestines of animals by making nutrients available  Human Uses #1: “Food Production” Food production – fermenting bacteria such as Lactobacillus are used in the production of cheese and yoghurt  Human Uses #2: “Biodegradation” Biodegradation – bacteria are used to eliminate a wide range of pollutants and waste from the environment (e.g. hydrocarbons, PCB`s, radioisotopes, plastics, and metals)  Human Uses #3: “Genetic Engineering” Genetic engineering – compounds such as insulin can be synthesized by inserting the human insulin gene into bacterial DNA  Human Uses #4: “Bioleaching” Bioleaching – the extraction of metal (e.g. copper) from their ores through the use of bacteria Bacterial Diseases  How Bacteria Cause Disease 1) Damage to cells and tissue 2) Release of toxins e.g. Mycobacterium tuberculosis e.g. Streptococcus (can release (destroys lung tissue) toxins into the bloodstream)  Controlling Bacteria 1. Physical removal by hand washing 2. Antiseptics 3) Disinfectants 4) Food storage 5) Food processing 6) Sterilization by heat Preventing and Treating Bacterial Diseases Prevention: Vaccination Treatment: Antibiotics  Human Bacterial Diseases Anthrax Listeriosis Salmonellosis Botulism Lyme Disease Scarlet Fever Bubonic Plague Meningitis Strep Throat Cholera MRSA Syphilis Diphtheria Necrotizing Tetanus Gonorrhea Fasciitis Tuberculosis Legionnaires Pneumonia Whooping Disease Rocky Mountain Cough Spotted Fever Kingdom Protista  Kingdom Protista Kingdom Protista – all members are single- celled, eukaryotic organisms collectively known as the “protozoans”  Animal-like Protists 1) Phylum Zoomastigina 2) Phylum Sarcodina 3) Phylum Ciliophora 4) Phylum Sporozoa  1) Phylum Zoomastigina Phylum Zoomastigina – members are animal-like protists that swim by using whip-like projections called flagella feed by absorbing food through their cell membranes Trypanosoma (causes African collectively known as the Sleeping Sickness; vector is “zooflagellates” the Tsetse fly)  2) Phylum Sarcodina Phylum Sarcodina – members are animal-like protists that use pseudopods for movement and feeding pseudopods (“false foot”) are temporary cytoplasmic projections Amoeba collectively known as the “sarcodines”  3) Phylum Ciliophora Phylum Ciliophora – members are animal-like protists that use short, hair-like projections called cilia for movement and feeding collectively known as the “ciliates” Paramecium  4) Phylum Sporozoa Phylum Sporozoa – members are animal-like protists that have no cilia nor flagella and are all parasites collectively known as the “sporozoans” Plasmodium (causes Malaria; vector is the mosquito)  Plant-like Protists 1) Phylum Euglenophyta 2) Phylum Chrysophyta 3) Phylum Pyrrophyta  1) Phylum Euglenophyta Phylum Euglenophyta – members are plant-like protists that have chloroplasts, two flagella, and sometimes a red eyespot collectively known as the “euglenophytes” Euglena  2) Phylum Chrysophyta Phylum Chrysophyta – members are plant-like protists such as the diatoms which produce thin cell walls rich in silicon (i.e. glass) collectively known as the “chrysophytes” Diatoms  3) Phylum Pyrrophyta Phylum Pyrrophyta – members are plant-like protists that usually have two flagella wrapped around two thick plates some are bioluminescent, others cause “PSP” collectively known as the Gonyaulax (causes “PSP”) “dinoflagellates”  Fungus-like Protists 1) Phylum Acrasiomycota 2) Phylum Myxomycota  1) Phylum Acrasiomycota Phylum Acrasiomycota – members are fungus-like protists they form a large mass with cells that have distinct boundaries collectively known as the “cellular slime moulds” Cellular slime mould  2) Phylum Myxomycota Phylum Myxomycota – members are fungus-like protists they form a large multinucleate mass with no distinct boundaries between cells collectively known as the Acellular slime mould “acellular slime moulds”