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