Antimicrobial agentsAntimicrobial agents

• DisinfectantsDisinfectants– 1 – Bleach– 2 – Ammonia– 3 – 409– 4 – Sterile water

• AntisepticsAntiseptics– 1 – Hand gel– 2 – Iodine– 3 – Alcohol– 4 – Sterile water

• AntibioticsAntibiotics– 1 – Streptomycin– 2 – Erythromycin– 3 – Tetracycline– 4 – Sterile water

• BacteriaBacteria– Bacillus cereus– E. coli– Serratia marcsens

Antiseptic CC Disinfectant CC Antibiotic CC

E. coli E. coliE. coli

1

42

3

111

222

33 3

4 4 4

Bacteria Objectives

• What are some common ways to identify bacteria?

• Describe the structure of bacteria.

• What are some ways in which bacteria reproduce?

• How are bacteria important to us?

How are bacteria classified?• Domain Archaea

– Kingdom – Archaebacteria

• Lack Peptidoglycan (protein & carbohydrate) in cell wall

• Extremophiles - – Halophiles (love salt), – Methanogens (convert H2 & CO2 into

methane gas), – Thermoacidophiles (love acidic & hot

environments)

• First organisms to colonize primitive earth

Mouth of a geyser

Domain – BacteriaKingdom – Eubacteria

• Eu = True

• 3 basic shapes 1. Bacilli – rod shaped. E. coli, Bacillus

anthracis

2. Cocci – spherical shaped. Staphylococcus aureus, Streptococcus pyogenes

3. Spirilla – spiral shaped. Spirochette, Syphilis

Staining properties • Groups Eubacteria in two groups

– Gram Staining• Gram Positive – Gram stain purple with

Crystal violet due to thick layer of peptidoglycan. Easier to kill with antibiotics

• Gram Negative – Gram stain pink with Safarin. Hard to kill with antibiotics due to thin layer of peptidoglycan

Gram Positive Gram Negative

Basic Structure

• Cell Wall,

• Plasma membrane

• Ribosomes

• Circular DNA

• Pili (hairs) for adherence to host cells

• Flagella (protein) for movement, capsule (made of polysaccharides) for attachment.

Endospores

• Produced by Gram + (usually Bacillus & Clostridium)

• Dormant structure to survive adverse conditions (heat, cold, dryness). Vegetative cell (2N), not reproductive

Bacillus anthracis

Methods of Respiration 1. Obligate aerobic bacteria must have

oxygen; (tuberculosis bacteria) 2. Obligate anaerobes die if oxygen is

present; (tetanus bacteria that causes lockjaw)

3. Facultative anaerobes do not need oxygen, but don’t die if oxygen is present; (E. coli)

4. Anaerobes carry on fermentation, while aerobes carry on cellular respiration 

Nutrition

• Heterotrophic or autotrophic • Saprophytes – feed off dead, decaying

material• Autotrophs – capable of making their own

food, photoautotroph photosynthesize, or chemoautotrophs oxidize inorganic compounds to produce energy (ammonia (NH3) to form nitrite (NO2) to get energy

Reproduction1. Asexually by binary fission

• Conjugation - Sexual reproductive method . Two bacteria form a conjugation bridge or tube between them

– Pili hold the bacteria together – DNA is transferred from

one bacteria to the other 

Transformation • Bacteria pick up pieces of DNA from

other dead bacterial cells

• New bacterium is genetically different from original

Bacteria and Humans

• Pathogens – disease causing agents (Pathology – science of studying diseases)

• Can produce poisonous toxins (poisons) • Endotoxins are made of lipids &

carbohydrates by Gram - bacteria & released after the bacteria die (cause high fever, circulatory vessel damage…) E. coli  

• Exotoxins are made of protein by Gram + bacteria . Secreted into environment. Clostridium tetani

To fight them:

• Antibiotics interfere with cellular functions (Penicillin interferes with synthesis of the cell wall; tetracycline interferes with protein synthesis)

• Some antibiotics are made by Actinomycetes bacteria or fungi

• Broad-spectrum antibiotics affect a wide variety of organisms

• Bacteria can mutate and become antibiotic resistant (often results from overuse of antibiotics)

Helpful Bacteria:

1. Bacteria of decay2. Nitrogen fixing bacteria (Legumes)

Rhizobium3. Fermentation of milk products – sour

cream, yogurt, buttermilk4. Production of cheese5. Fermentation to produce wine,

sauerkraut, pickles6. Mining and oil spill cleanup

Bioremediation

7. Biotechnology

Diseases caused by bacteria

• Anthrax• Botulism• Cholera• Cavities• Gonorrhea• Syphilis• Tetanus• Staph Infection (MRSA)• Food Poisoning• Lyme Disease• Diphtheria• Tuberculosis• Escherichia coli O157: H7• Leprosy• Meningitis• Strep throat• Whooping cough (Pertussis)

Food poisoningFood poisoning • Results from decay of foods and

production of toxins

• 33 million people/yr get “stomach flu”

• Seafood accounts for 20 – 25% of cases

• 33% of all raw poultry tests + for Staphylococcus

• 1 in every 200 eggs has Salmonella

4 C’s of Food Safety

Chill your foods

Cook your food to the proper

temperature

Clean food and cooking surfaces

Combat Cross Contamination

Antibacterial AgentsAntibacterial Agents

• Antibiotics – organic substance that inhibits growth in/on living material. Penicillin

• Disinfectants – inhibits growth on a non-living surface – bleach, ammonia

• Antiseptics– inhibits growth on a living surface – alcohol, hydrogen peroxide

• Sterilization – high heat or chemicals that kills bacteria

Chapter 24: Viruses

Virus Objectives

• What is a virus?

• Describe the typical structure of viruses.

• Compare/contrast lytic and lysogenic viral cycles.

• How are viruses important to us?

• Name some viruses and their action.

Stanley (1935)

• Crystallized tobacco mosaic virus.

• Living cells don’t form crystals

• Named them virus meaning Poison

Living or non-living?

• Neither! • It’s a non-

living pathogenic particle made of a protein coat & a nucleic acid

Characteristic of life

Virus Bacteria

Growth No Yes

Homeostasis No Yes

Metabolism No Yes

Mutation Yes Yes

Nucleic acid DNA or RNA DNA (and RNA)

ReproductionOnly within a host

cellIndependently by cell

division

StructureNucleic acid w/I

capsidprokaryotic cell

• A virion = a single virus particle• - Small - 20 nm (polio virus) - 350 nm (small

pox virus) - Single type of nucleic acid (RNA or DNA but

never both) - Protein coat – capsid- Some have envelopes (made of lipids) outside of capsid- Surface projections made up of glycoproteins for attachment onto host cells - Are specific to their host

Virus Structure

• Icosahedral –– 20 triangular faces – Polio, herpes,

chicken pox, cancer, AIDs, hepatitis, Respiratory infections (the cold)

– Brick shaped – small pox, cowpox– Helical – TMV, measles, rabies, influenza

• Viruses are classified by their shape and structure

• If it contains DNA:– Host cell may produce RNA to make more viral

proteins in host cell– Join with host’s DNA to direct the production of

virions (viral particles)• If it contains RNA:

– RetrovirusesRetroviruses – such as HIV. Viral RNA uses host’s ribosomes for viral protein synthesis

– Reverse transcriptase – viral enzyme that uses RNA as template to make DNA. Then DNA integrates into host DNA and then when triggered, normal transcription occurs with the production of RNA and translation to produce new viruses. RNA to DNA to RNA to protein.

– Normal is DNA to RNA to protein.

Human Immunodeficiency Virus (HIV)

A BacteriophageA Bacteriophage  • Host is E. coli

Head

Tail w/ Tail Fibers

The Lytic Cycle • Get in, replicate and get out to invade other host cells –

Virulent (Disease causing)• The cold, rubella (German measles), mumps

ReleaseAttachment at Receptor site

Entry

Replication

Assembly

The Lytic Cycle of Virus infection

Attaches onto host cell Injects DNA into host cell Replication of Viral parts

Reassembly of virons Lysis – bursting out

Viruses that reproduce only b y the lytic cycle are called Virulent

Lysogenic Cycle• Infect cell but do not cause disease immediately. Instead, they

incorporate their nucleic acid into host’s for extended periods of time (sometimes years).

• May turn lytic or stay incorporated depending on conditions. • Temperate viruses - AIDS, cold sores, chicken pox, hepatitis

Prophage

Attachment Integration Cell multiplication& Injection of nucleic acid Prophage remains unnoticed and not transcribed. Occurs in bacterial DNA

Lytic and Lysogenic Cycles

So are we going to just sit back and let them cause diseases in us?

Prevention:• Antiviral drugs – not a lot since viruses aren’t living.

Basically change the receptor sites• Vaccines – either inactivated (dead viral particles) or

attenuated (weakened or altered viral particles) are injected into organism. Body starts the production of antibodies and memory cells to combat viral invaders when needed.

Diseases caused by viruses• AIDS• The Cold• Measles• Mumps• Rubella• Chicken pox/Shingles• Small Pox• Hepatitis• SARS• The Flu• Ebola• HPV• Bird Flu• Polio• Swine flu

Polio and the Iron Lung

• Viroids – another disease causing agent but no capsid, only the RNA. Found only in plants

• Prion – viral proteins that are able to cause diseases by clumping together within cell. 250 amino acids but no nucleic acid. – Scrapie in sheep degrades nervous system. – Mad Cow disease (Bovine spongiform

encephalopathy) in cows – puts holes into brain.– In humans, its Creutzfeld-Jakob disease.