Unit 7 Microbiology
Viruses
• Viruses exhibit some but not all of the characteristics of living things.
• Viruses reproduce themselves but only in a • Host cell.
• Size of Viruses .01 micrometers to over 0.3 micrometers (Over 500 of them can fit on the tip of a pin!)
Structure and Shape of Viruses• Consist of two parts
• 1. Inner Core of nucleic acid• 2. Protective outer coat of protein
• The Outer protein coat is called the• capsid (95% of virus)
• Shapes vary – polyhedral, rod, etc.
• Viruses that attack bacteria =
• Bacteriophages
• Reproductive Cycles of the virus
• Lytic Cycle
• 1. Adsorption-Viral DNA Plasmid enters the Host
• 2. Entry- Viral DNA attaches to host DNA and changes the Genetic Code
• 3. Replication- Host’s changed DNA begins to make new Viral DNA
• 4. Assembly Viruses begin to replicate
• 5. Release-The cells bursts and small Viruses are released
Lysogenic cycle• Some remain inactive for many generations
• Suddenly become active – Temperate phases
• Example = Lyme’s Disease• 1. Attachment-Virus attaches to the host cell
• 2. Replication-Viral DNA is replicated in cell, but can stay inactive for extended periods of time
• 3. Activation-At a period of time, the virus will go from inactive to active and begin replication
• Transduction – when host genes are passed with the viral DNA
• Through transduction a virus can alter the hereditary code of a cell.
• Cystic Fibrosis treatment
• Retroviruses – Contain RNA instead of DNA
Prions
• Prions are Mutated Infectious proteins that cause transmissible spongiform encephalopathies (Spongy Brain) including:
• Humans: Creutzfeldt-Jakob Disease• Deer and Elk = Chronic Wasting Disease
(CWD)
Viruses and Disease
• Viruses that cause disease are called Pathogens• • Tobacco mosaic virus – fluid from diseased plant• • Range from minor cold to cancer.• • The ability of a virus to cause disease is called• Virulence
Your Defenses
The body provides its own best defense against viral disease• Natural resistance is called
Immunity • First line of defense• Skin, Mucus, Hair
Antibodies
• The foreign virus protein is called• antigens• The antigen triggers the production of• antibodies• Virus are either destroyed or marked for
the phagocytes.
• Immunity to a disease resulting from the production of antibodies.
• active immunity
• A vaccine is a solution of dead virus
• When a person gets antibodies from another it is
• Passive Immunity• (babies right after birth)
• Interferon – interferes with viral replication and recognition.
Structure of a Bacteriophage
•
The Kingdom Monera
• Microbes – Where do they live?• Almost Everywhere!• All are Prokaryotes and all have nucleic acid.
• Classification:• These have actually become two Kingdoms (domains)
• 1. Archaebacteria
• 2. Eubacteria
• a. Phylum Schizophyta
• b. Phylum Cyanophyta (Cyanobacteria)• (photosynthetic)
• c. Phylum Prochlorophyta• (different pigment)
• Monera – used to be grouped by size, shape and movement but are now grouped according to
• Biochemical processes (what they eat and what they produce
• Bacteria• Size and Shape
• Three basic Shapes
• 1. Cocci – Sphere shaped
• Diplococci-2 cocci bacteria stuck together
• Staphylococci- clusters of cocci bacteria
• Streptococci-long line of bacteria
• 2. Bacilli – Rod Shaped• Look Like small pills
• 3. Spirilla – • corkscrew shaped• Salmonella is a common spirilla• Found on raw meat (particularly poultry)
Structure• Some have rigid and others flexible cell walls.
• Large Amounts of peptidoglycan= Bacteria stain dark purple in Gram Staining• Small amounts of peptidoglycan=Bacteria appear light pink during Gram staining process
• A slime layer that surround the outer surface – protective coat is called a
• Capsule.
• Cytoplasm contains: Ribosomes, Chromosomes, and usually some separate DNA
• Some DNA exists as plasmids (circular segments of DNA)
• These are circular and self reproducing – one bacteria can have 12 different ones.
• Flagella - are thin extensions
• Pili - are shorter and more numerous
• Low levels of Peptidoglycan
High Levels of Peptidoglycan
Movement• Not all are capable of movement
• Motile - those that move
• Nonmotile - those that don’t move
• Gliding over a slime layer• Twisting and turning• Flagella
Nutrition
• Some are autrotrophic (like plants) (produce their own food)
• Derive energy from The Sun or
• Derive energy from breakdown of inorganic molecules (Chemosynthesis)
• Others are Heterotrophic (depend on autotrophs)
• Enzymes allow them to digest certain food (cellulose etc)
Heterotrophic Bacteria
• Feed on Dead organisms
• Called• Saprophytes: recycle nutrients
• (live in soil, rotting food and intestines of animals)
Photosynthetic Bacteria• Different pigments than plants – purple sulfur bacteria (carotenes)
• Do not use water and do not produce oxygen as a byproduct.
• Sulfur bacteria use• Carbon Dioxide and Hydrogen Sulfide and produce Carbohydrates
using sunlight•
• Equation :• CO2 + 2H2S (CH20) + H2O + 2S
Purple Sulfur Bacteria
Chemosynthetic Bacteria
• Use different energy sources – includes nitrogen and sulfur compounds
•Methanogens (mud at bottom of swamps)
Heterotrophic and Photosynthetic bacteria
Respiration• Require oxygen
• Obligate aerobes: live where there is oxygen
• Example: Mycobacterium tuberculosis
•
• No oxygen:
• Obligate anaerobes: little to no oxygenExample: Clostridium botulism
•
• With or without Oxygen• Facultative anaerobes
• Example: Escherichia coli
Growth
• Usually refers to an increase in the number of bacteria
• Colony = a large group of bacteria
• grow on nutrient plate•All members are descendants of a single bacterium (clone)
• All bacteria need food and water – maybe oxygen, Temperature, sunlight and chemicals.
• Special Spores Called Endospores –
• formed to survive in harsh environments. Cell membrane and coat forms around 1 strand of DNA.
• Freeze Dried
Endospores in blue
Slide #1
Slide #2
• GroupBacillusName:Staphlo-Bacillus
Slide #3
• Group:• Spirilla• Name• Salmonella