Lecture #2: Evolution & History of Microbiology

Question 1

Study of Disease

Answer 1

Spread, containment, treatment, evolution, recognition. Historically, linked to disease—generally human disease. Keen interest in keeping people alive and well, and easing their suffering. Target of funding.

Techniques
- Identification of microbes and of their capabilities. - Culture.
- Safe handling of organisms that are invisible to the naked eye, and, often, highly contagious and downright dangerous. Containment.
Use of microbes to benefit mankind.

Question 2

Protists

Answer 2

Mostly unicellular eukaryotic organisms that lack cellular differentiation into tissues. Cell differentiation is limited to cells involved in sexual reproduction, alternate vegetative morphology, or resting states such as cysts; includes organisms often referred to as algae and protozoa.

Question 3

Protozoa

Answer 3

They are unicellular, animal-like protists that are usually motile. Many free living protozoa function as the principal hunters and grazers of the microbial world.

They obtain nutrients by ingesting organic matter and other microbes.

They can be found in many different environments, and some are normal inhabitants of the intestinal tracts or animals, where they aid in digestion of complex materials such as cellulose.

A few cause disease in humans and other animals.

Question 4

Fungi

Answer 4

A diverse group of eukaryotic microorganisms that range from unicellular forms (yeasts) to multicellular molds and mushrooms.

Molds and mushrooms are multicellular fungi that form thin, threadlike structures called hyphae.

They absorb nutrients from their environment, including the organic material molecules that they use as sources of carbon and energy.

Because of their metabolic capabilities, many fungi play beneficial roles, including making bread rise, producing antibiotics, and decomposing dead organisms.

Some fungi associate with plant roots to form mycorrhizae. Mycorrhizal fungi transfer nutrients to roots, improving growth of plants, especially in poor soils.

Other fungi cause plant diseases (rests, powdery, mildews, and smuts) and diseases in humans and other animals.

Fungi Infectious as Spores or One to Few Celled Units are Microbes

Question 5

Valley Fever

Answer 5

Valley Fever is caused by soil fungi. Spores are inhaled and lead to a dangerous respiratory disease.

Question 6

Ringworm

Answer 6

Ringworm, Athlete’s Foot, caused by fungi that attack skin.

Question 7

Worms

Answer 7

Animal microbes. Hookworms, pinworms, filarial worms including heartworm.

Question 8

Biological Safety Levels

Answer 8

There are 4, increasingly restrictive. Used nationwide (American Biological Safety Association).

Key considerations are the potential for causing disease, severity of the disease, likelihood of infection through aerosol transmission, difficulty of containment/ease of spread of the disease, whether or not there is a cure or treatment.

Labs must be equipped relative to BSL.

Question 9

BSL 1

Answer 9

Microbe does not cause disease in a typical, healthy adult. No aerosol transmission. Little hazard.

Open lab bench, normal traffic, standard protection & washing/disinfection.

Bacteriophages (viruses that attack bacteria, Escherichia coli.

Question 10

BSL 2

Answer 10

BSL 2 – Microbe causes mild disease in a typical, healthy adult. Limited aerosol transmission. Moderate hazard.

Access restricted to trained personnel when microbes present, aerosol generating work in safe areas (Hoods), attention to contaminated materials with thorough disinfection/routed NOT through regular trash.
MRSA, Lyme spirochaete (Borrelia), Influenza A (common cold).

Question 11

BSL 3

Answer 11

Microbe may cause serious disease or be potentially lethal if inhaled by a typical, healthy adult but for which treatment is available. Serious hazard.

Personnel specifically trained and supervised by scientists whose primary work is with the specific pathogen or disease, restricted and filtered airflow in the room and all work within Safety Cabinets.

TB, various Encephalitis pathogens, SARS.

Question 12

BSL 4

Answer 12

Microbe causes serious disease or is lethal if inhaled by a typical, healthy adult and for which no treatment is available. Extreme hazard.

Multiple airlocks, mandatory use of a Hazmat Suit and Oxygen Pack. UV Light Treatment, and Specific Showers prior to exit. Complete isolation.

Ebola, Hemorrhagic Fevers.

Question 13

Scientific Names

Answer 13

Linnaeus and the binomial system.

A species is 2 words. First word is the genus and is capitalized. Second is the specific epithet and is NOT capitalized. Both are either underlined or italicized.

Question 14

Microbial Evolution

Answer 14

Great Oxygenation Event (G.O.E.) imposed selection that favored eukaryotes.

First prokaryotes, metabolic experimenters, diversity of forms adapted to distinct environmental niches.

Question 15

Stromatolites and Cyanobacteria

Answer 15

Photosynthetic bacterial fossils and early Archaean forms deep in these formations, date back to at least 2.5 billion years ago. Shallow waters with abundant light.

Question 16

Cyanobacteria

Answer 16

Once called blue-green algae. It produces significant amounts of oxygen through oxygenic photosynthesis.

Question 17

Antony von Leeuwenhoek

Answer 17

(1632-1723) From Deft, the Netherlands. He earned his living as a draper and haberdasher (a dealer in men’s clothing and accessories) but spent much of his spare time constructing simple microscopes composed of double convex glass lenses held between two silver plates. His microscopes could magnify 50 to 300 times, and he may have illuminated his liquid specimens by placing them between 2 pieces of glass and shining light on them at a 45 degree angle to the specimen plane. This provided a form of dark-field illumination in which the organisms were bright colors against a dark background.

Beginning 1673, Leeuwenhoek sent detailed letters describing his discoveries to the Royal Society of London.

first living cells in a drop of pond water described, drawn and presented to the Royal Society of London. 1676, ‘animalcules.’ Lens grinding superior to others.

Question 18

The Electron Microscope

Answer 18

Developed in mid-1900’s.

Light Microscope resolves well to about 0.2 microns, and bacteria are about 0.1 micron in diameter (10 microns long). See shape, outside features.

Viruses are 1-10 nanometers in size. They could not be visualized until resolution improved. EM led to understanding of diversity of viruses.

Question 19

Spontaneous Generation

Answer 19

An early belief, now discredited, that living organisms could develop from nonliving matter.

Evidence:
Hay, dirty shirts or old meat gives rise to maggots, flies, worms or mold.
Life appears magically each spring in ponds dead over the winter, so mud and water gives rise to life. (Pond weeds, algae, frogs…)

Question 20

Koch’s Postulates

Answer 20

Microbe present in diseased individuals.

Microbe can be isolated in pure culture.

Same disease results when microbe introduced into healthy individual.

Same microbe can then be isolated from the newly diseased individual.

Question 21

Koch’s Postulates Can Be Difficult to Impossible to Realize

Answer 21

Many microbes will not grow outside the target organism. Can’t get them in pure culture.

Some have specific triggers for virulence or go into remission.

Some behave differently in alternate hosts.

Some are obligate human pathogens and so deadly that to test them on a human is certain death.