Chapter 19Viruses & Bacteria

A. Viral Life Functions (?)

1. Viruses require NO food or water– DO NOT require or release

energy– DO NOT excrete any wastes– DO NOT secrete any

hormones, enzymes, or juice– DO NOT exchange any gases

2. ARE THEY ALIVE? _____

B. Comparison of Viruses with Cells

• Viruses lack cytoplasm, cell membrane, & ribosomes like cells have

• Viruses DO NOT grow or carry out metabolic reactions like cells do

• Viruses have only one kind of nucleic acid (either DNA or RNA); cells contain both

• Viruses have few or no enzymes; cells have many• Viruses can be crystallized and reactivated later; cells

cannot• Viruses DO NOT develop directly from an existing virus;

cells come only from other living cells

C. Search for Viral Structure (along with disease protection)

• Early Chinese would use dried scads of smallpox to “dust” their young in hopes that they would not suffer severe smallpox infections- process was called “variolation” in England (1717)

• Edward Jenner began “vaccination” (1780) by using pus from cowpox infection to furnish protection against smallpox

• Louis Pasteur prepared live weakened rabies virus vaccine (1885)

• Wendell Stanley prepared tobacco mosaic virus (TMV) in a pure crystalline form; then added water- could still infect tobacco plants (How could a non-living chemical cause infectious disease?)

D. Viral Classification/Taxonomy

• A variety of classification systems are used (none listed in text) size, shape, kind of nucleic acid

• Envelope present

• Type of host

• Type of tissue infected

• How it is transmitted

E. Basic Viral Structure/Composition1. Made up of 2 basic molecules- outer

coat (protein) & inner core (nucleic acid)2. Other structural details• Capsid protein sheath surrounding

nucleic acid (either DNA or RNA) single stranded

• Envelope membrane surrounding capsid (proteins, lipids, glycoproteins)

• Glycoproteins (carbohydrates + proteins) & GP 160 (recognize special CD 4 protein found on some white blood cells & helper T-cells)

• HIV contains enzymes (reverse transcriptase) for viral replication

E. Cont. Basic Viral Structure/ Composition

3. Viral shapes and geometric symmetry• Three basic shapes: (from simple to complex)

1. Helical (TMV) coil of nucleic acids + coat2. Cubic (Adenovirus) polyhedrons- faces + corners (icosahedrons- 20 faces & 12 corners)3. Complex (T2 bacteriophage)- complex head with tail

F. Viral Reproduction (can ONLY reproduce inside a living host cell)

• Viruses are very specific as to host or target they infect- only certain organisms or kind of tissue

• Ex: Bacteriophage (bacteria); Polio (nerve tissue); Rhinovirus (respiratory membrane)

• Viral infection may be lytic or lysogenic (Hershey & Chase Exp)

• Viral genetic material must be replicated and translated in host- normal flow of information “central dogma” (from DNA RNA PROTEIN) in most viruses just like prokaryotic & eukaryotic cells = but there are a few viruses

Cont. F. Viral Reproduction (can ONLY reproduce inside a living host cell)

• Retroviruses where information flows differently (from RNA DNA RNA PROTEIN)

• The HIV is an RNA virus and contains an enzyme reverse transcriptase (RNA DNA)

G. Protection from Viral Infection (Prevention/treatment mainly)

• Immunity (acquired- vaccination or previous occurrences; natural- genetic)

• Interferon & protease inhibitors- viral “cocktails” for HIV

• Antibiotics are NOT effective (NO METABOLIC PROCESSES)- not many cures available, if any

• Drug store is full of chemicals providing temporary symptomatic relief- analgesics (pain), antipyretics (fever), antihistamines (fluids), antitussives (coughs)

H. Economic Importance of Viruses

• Viral disease plague humans from conception to death- they also affect many other plants & animals that humans value or need

• Viruses can be used as “vectors” to move genetic material between species (Hershey/Chase Transduction EXP) or moving human genes for making growth hormone or insulin into bacteria or yeast cells

• Development of vaccines- studying and growing viruses in viruses living cells (ex: tissue culture, chick embryos, monkeys, mice)

Viral Diseases

Measles Yellow Fever Chicken Pox Influenza

Small Pox Common Cold Fever Blisters Sinusitis

Cold Sores Distemper (Dogs)

Encephalitis HIV (AIDS)

Meningitis Hepatitis Poliomyelitis (Polio)

Some Leukemia

Hydrophobia (Rabies)

Ebola Mumps Hanta Virus

Mononucleosis Warts

Measles

Smallpox

Measles

Polio

Deformed leg due to Polio

Women suffering from liver cancer caused by Hepatitis B.

Ebola Virus

A. Origin of Present Day Bacteria & Eukaryotic from Early Cells

1. The first cells Prokaryotes included 2 types of bacteria

• Archaebacteria & Eubacteria: some Eubacteria (cyanobacteria) were photosynthetic and probably gave rise to chloroplasts,

• while other Eubacteria might have formed mitochondria- both of which could have developed inside Eukaryotic cells

2. Archaebacteria, Cyanobacteria, other kinds of Eubacteria, and Eukaryotes all survive today

3. Characteristics of Archeabacteria• Unicellular prokaryotes• Cell walls lack peptidoglycan (polysaccharides

+ short amino acid chains)• Genes have introns (will allow for mRNA

processing)• May be autotrophic or heterotrophic• 3 groups that live in extreme environments

(similar to early Earth)– Methanogens obligate anaerobes

(poisoned by O2)/ marshes, sewers, intestines

– Extreme halophiles high salt concentration (10X sea H2O)/ Dead Sea, Salt Lake

– Thermoachidophiles Low pH (2-4), hot (60-80oC)/ hot springs, Yellowstone Park

4. Characteristics of Eubacteria

• Unicellular prokaryotes

• Cell walls have peptidoglycan

• Maybe be autotrophic or heterotrophic

• Genes lack introns (no mRNA processing)

• Cell membrane might contain lipoplysaccharides (polysaccharides + lipids)

B. Three Basic Shapes (individual cells)

• Coccus (round), Bacillus (rod), Spirillum (spiral or spirochete)

• Sometimes grouping may occur– Staphylococcus (clumps of 4-

8 cocci)

– Streptococcus (chain of 10 or more cocci)

Prokaryotic Shapes

Prokaryotic Growth and Reproduction• Binary Fission asexual

reproduction in which the DNA is duplicated and the cell divides in half, producing two identical “daughter” cells

• Conjugation sexual reproduction in which genetic material is exchanged between two cells via a hollow bridge

C. Conditions Needed for Growth for most Eubacteria

• Temperature, moisture, simple nutrients, darkness

D. Ways of Preserving Food to Prevent Bacterial Contamination

• Canning, freezing, salting, drying, radiation, chemicals, pH (acids)

E. Bacteria Nutrition (how they obtain energy)

• Autotrophs (chemoautotrophic, photosynthetic) producers

• Heterotrophs (decomposers- saprophytes; parasites) MOSTLY consumers

F. Kinds of Bacterial Respiration (ATP Synthesis)

1. Aerobic need O2/ Diphtheria, tuberculosis

2. Anaerobic no O2/ tetanus, botulism

G. Some Bacteria Have a Gelatinous Outer Covering (capsule) that Introduces Variation

• Others might form endospores a structure that gives high resistance to extremely high temperatures (especially in clostridium bacteria- those that cause tetanus (lockjaw) and botulism (severe food infection)

A stained preparation of Bacillus subtilis showing endospores as green and the vegetative cell as red

H. Special Instruments Used in Hospitals and Labs to Sterilize Equipment

• Autoclave uses heat, pressure, + timed and then reheated

H. Special Instruments Used in Hospitals and Labs to Sterilize Equipment

• Autoclave uses heat, pressure, + timed and then reheated

I. Economic Importance of Bacteria• Can make or spoil food- cheese, yogurt, sauerkraut, and

pickles/ or can cause food decay (making it unfit for consumption)

• Can be used to cause or cure disease (pathogens, antibiotics)

• Can chemically enrich (decomposers) or pollute the environment

• Genetic research- biotechnology/ vaccine/ hormone production

• Many other industrial/manufacturing applications- sewage treatment, breaking down grease & oil, alcoholic fermentation, agriculture (nitrogen fixers), mining, etc.

• Bacteria Differ in Cell Wall Structure (See #3 & #4)- GRAM STAINING– If cell walls have thick layers of peptidoglycan then a

gram stain dye (violet) will be absorbed and cells will appear purple bacteria are GRAM POSITIVE

– If cell wall has very thin layer of peptidoglycan (thick lipopolysaccharide in outer membrane) then a gram stain dye (red) will be absorbed and cell will appear red bacteria are GRAM NEGATIVE

Cont. Gram-Staining• Gram staining identifies bacteria- those bacteria that

those are gram negative are resistant to many antibiotics and those that are gram positive are susceptible to many antibiotics- antibiotics influence cell wall synthesis (products if fungi) and do NOT affect Gram Negative bacteria

• Staphylococcus on the left is Gram positive and has been stained purple.  • E. coli on the left however has not been stained purple as it is a Gram negative bacteria

• Both Gram positive and negative bacteria contain peptidoglycan in the cell wall, but in the Gram negative, various other layers protect it and so the stain cannot reach it to cause the coloration.

Bacterial Diseases

Bubonic Plague

Whooping Cough

Acne Botulism

Rheumatic Fever

Tetanus (Lockjaw)

Gonorrhea Gangrene

Typhoid Fever

Dysentery Pneumonia Strep Throat

Diphtheria Tonsillitis Pinkeye TuberculosisTooth Decay Scarlet Fever Salmonella Ulcers

Syphilis Cholera Anthrax Boils

Acne Propionibacterium acnes (pores)

Lyme Disease

• Certain ticks, found on deer, harbor the bacterium in their stomachs. Lyme disease is spread by these ticks when they bite the skin, which permits the bacterium to infect the body. Lyme disease is not contagious from an infected person to someone else. Lyme disease can cause abnormalities in the skin, joints, heart, and nervous system.

Tuberculosis (TB) Mycobacterium tuberculosis

Tetanus caused be C. tetani

• Child experiencing severe muscle contractions

Scarlet fever (Streptococcus pyogenes)

Diphtheria(Corynebacterium diphtheria)

• Sore throat, low fever, fatigue

• Later stage: characteristic swollen neck, sometimes referred to as “bull neck”

Bubonic Plague (Yersinia pestis)

Anthrax (Bacillus anthrax)