Microbiology Exam 1- Lecture Material

Leeuwenhoek

-Described “animalcules” in specimen of lakewater

-Suggested maggots arose from eggs in decaying material, not from material itself

Redi

Found that if flies were prevented from landing on decaying material, no maggots were produced

Needham

Boiled media briefly, covered with gauze → bacterial growth

Spallanzani

Boiled media and left flasks open and closed— found no growth in closed flasks

Pasteur

-Filtered air through cotton, placed the cotton into sterile broth, found microbial growth

-Ran experiments in swan-neck flasks: upright = no growth, tipped flask = microbes in neck reached liquid and growth

-Disproved spontaneous generation

-Supported germ theory of disease

-Fermentation and pasteurization

-Anthrax and rabies vaccines

Pouchet

-Conducted similar experimentation to Pasteur’s swan-neck experiments but with boiled hay as media, always had microbial growth

Tyndall

-Figured out that spores from Pouchet’s hay samples likely escaped into his lab and contaminated equipment

-Series of boiling and cooling steps could completely prevent growth in contaminated flasks

Jenner

Determined disease (smallpox) could be prevented through vaccination w/similar but milder disease-causing agent (cowpox)

Was Jenner the first to discover vaccination?

No— Chinese had been practicing variolation for years

Semmelweis

-Practice of anatomic pathology in morgues coincided with increase in maternal deaths by childbed fever

-Started mandatory hand washing, deaths from childbed fever plummeted

John Snow

Determined cause of cholera transmission in London was a single water source through case tracking

Lister

Developed practice of chemical disinfection of external living surfaces (antisepsis)

Test of Pasteur’s Anthrax Vaccine

-Used 10 control sheep, 25 inoculated with anthrax vaccine, 25 uninoculated

-All 50 sheep injected with anthrax, those that weren’t inoculated died within 2 days

-Inoculated group suffered no ill effects!

Koch’s Postulate 1

Same microorganisms are present in every case of disease

Koch’s Postulate 2

Organism must be able to be grown in pure culture from diseased host

Koch’s Postulate 3

Same disease must be produced when pure culture is used to infect new host

Koch’s Postulate 4

Same organism must be recovered from newly infected host

Purpose of Koch’s Postulates

Formalized standards to link specific organisms with infectious diseases

Limitations of Koch’s Postulates

-If microorganism of interest can’t be cultured in lab

-If no suitable animal model exists for testing

-If infected individuals don’t always show symptoms

-If disease is polymicrobial

Ivanowsky and Beijerinck

Early observations of filterable viruses (showed liquid filtrate caused tobacco mosaic virus)

Reed

Found filterable virus to be cause of yellow fever in humans

Winogradsky

Recognized beneficial roles of nitrogen-fixing bacteria

What are the prokaryotic domains?

Bacteria and Archaea

Are viruses microbes and/or cells?

NO!

Protista

Single-celled protozoa and algae

Criteria for living

-Composed of one or more cells

-Able to reproduce

-Derive energy from metabolism

-Capable of maintaining homeostasis

-Undergo evolution over time

Do bacteria have cell wall?

Yes, almost all

Are bacteria capable of photosynthesis?

Some

Do archaea have cell wall?

Some

Are archaea capable of photosynthesis?

Some

Are protozoa prokaryotic or eukaryotic?

Eukaryotic

Do protozoa have cell walls?

In some life cycle stages

Are protozoa capable of photosynthesis?

No

Are fungi prokaryotic or eukaryotic?

Eukaryotic

Do fungi have cell walls?

Yes

Are fungi capable of photosynthesis?

No

Are algae prokaryotic or eukaryotic?

Eukaryotic

Do algae have cell walls?

Yes

Are algae capable of photosynthesis?

Yes

Are viruses prokaryotic or eukaryotic?

Neither— acellular

Do viruses have cell walls?

No

Are viruses capable of photosynthesis?

No

Are prions prokaryotic or eukaryotic?

Neither— acellular

Do prions have cell walls?

No

Are prions capable of photosynthesis?

No

Viroids

Infectious RNA particles that replicate when inoculated into plants, no protein capsid

Hypothesis of viroid origination

-Introns?

-Interacts with host cell RNA?

Prions

Infectious proteins

TSEs

Transmissible Spongiform Encephalopathies

What are TSEs?

Neurological degenerative diseases that can be transmitted within or between species

Prusiner

Discovered prions

Protein-only Hypothesis

Suggests prions are only composed of proteins and contain no nucleic acids

How do prions kill their hosts?

Abnormal prions form insoluble aggregates in the brain which leads to sponge-like holes in brain tissue —> nerve cell death

Luria and Dulbruck

Discovered bacteria can mutate spontaneously to generate resistance to viral infection, NOT in response to environment

Beadle and Tatum

Demonstrated that one gene codes for one enzyme

Erlich

Developed Salvarsan (chemical that cured syphilis)

Challenges to microbiology

-Global travel increases disease transmission

-Emerging and reemerging infectious disease

-Pathogens cause more than one disease

-Increased antibiotic resistance

Emerging Disease

Diseases recognized in human hosts for first time

Reemerging Disease

Diseases that existed in the past but are now showing resurgences in resistant forms and expansion in range

Zoonotic Disease

Diseases carried by animals crossed into humans

Bioterrorism

Intentional use of biological agents to cause fear or death

Examples of how microbes are beneficial

• Provide nutrients we can’t make ourselves

• Useful in food and fermentation

• Degrade organic molecules for reuse

• Genetic engineering —> recombinant hormones like insulin

• Bioremediation

• Antibiotic production

  • Gene therapy for certain diseases

Common features of life

• DNA is hereditary material that controls structure and function

• Biochemical reactions used for growth and energy conversion

• Respond to stimuli

• Reproduce

• Adapt between generations

• Interact with other organisms and environment

Homeostasis

Maintenance of stable internal environment

Similarities between prokaryotes and eukaryotes

• Genetic organization w/DNA in chromosomes

• Compartmentation with cell membranes

• Metabolic organization in cytoplasm

  • Protein synthesis with ribosomes

Structural distinctions between prokaryotes and eukaryotes

• Eukaryotes have membrane-bound organelles

• Eukaryotes have mitochondria for respiration

  • Prokaryotes use cytoplasm and cell membrane

Eukaryotic Flagella

Made of microtubules, beat in wave-like motion

Prokaryotic Flagella

Structurally different, provide rotational propeller-like force

Eukaryotic Cillia

Shorter microtubules, more numerous than flagella

Roles of cell walls

• Help maintain water balance

• Provide support

• Give cell shape

• Help resist lysis

Endosymbiosis Theory

Eukaryotic organelles (i.e. chloroplasts and mitochondria) evolved by endosymbiosis from prokaryotic cells that were engulfed by proto-eukaryotes

Supporting evidence for endosymbiosis theory

• Mitochondria and chloroplasts have own genome

• Circular genome

• Mitochondria and chloroplasts divide by binary fission

• Mitochondria and chloroplasts are similar in size to bacteria

• Mitochondria and chromosomes express prokaryotic ribosomes

• M + C lack nuclear envelope

Evidence critical of endosymbiosis theory

Genomes of mitochondria and chloroplasts are more similar to bacterial genome than organism in question (keep their own genome)

Haeckel

Coined term “protist” for all microorganisms

Whittaker

Developed five-kingdom system:

1. Plantae

2. Animalia

3. Protista

4. Fungi

5. Bacteria

Woese

Used 16S rRNA to identify unique Archaea, replaced five kingdoms with three domains:

1. Bacteria

2. Archaea

3. Eukarya

Taxonomy

Science of classification, used to arrange related organisms into categories

Linnaeus

Established uniform binomial nomenclature for organisms

E. coli O157:H7

Particular strain capable of causing severe diarrhea and kidney damage, different O and H antigens

EHEC and example

Enterohemmorhagic E. coli (O157:H7)

Reservoir of EHEC

Cattle

Shiga Toxins

A-B toxins that bind to 28S rRNA and disrupt protein synthesis

Magnification

How large you can make an image

Resolution

How clearly you can see an image

Purpose of oil immersion

Oil bends light rays into lens, increasing resolution

Resolving Power

wavelength / (2X NA)

Restriction of resolving power

Range only from 400-700 nm of light (visible)

Empty Magnification

Increasing magnification only causes image to become more magnified, with no increase in resolution detail

Simple Stain

Use of basic dye to distinguish microorganisms from background

Differential Stain

Distinguishes groups of microorganisms from one another

Special Stain

Reveals special structures in or outside cell

Negative Stain

Uses acid dye (repelled by cell walls) which leaves clear cells on dark background

Gram Stain Technique

1. Stain cells with crystal violet

2. Stain cells with Gram’s iodine

3. Wash cells with decolorizer

4. Counterstain cells with safranin

Gram Stain Results

Violet = Gm+

Pink = Gm-

Endospore Staining

Used to identify endospores of Gm+ bacteria

Phase Contrast Microscopy

Special condenser and objective lenses allow observers to view living, unstained organisms

Dark-Field Microscopy

Shows specimen against dark background

Fluorescent Microscopy

Specimens coated with fluorescent dye and illuminated with UV light

Electron Microscopy

Electrons are absorbed, deflected, or transmitted based on density of specimen structures

Hyphae

Branching filaments that make up fungal mycelium