micro lecture 1

what is microbiology

study of microorganisms (organisms too small to be seen with the naked eye)

size range of microorganisms

atoms/molecules, viruses, bacteria, eukaryotic cells, multicellular organisms

1um

10^-6m

1nm

10^-9m

1 A

10^-10m

what are the two main groups of microorganisms

cellular (prokaryotes and eukaryotes) and acellular(viruses, viroids, and prions aka non-living infectious agents)

prokaryotes

archaea and bacteria

eukaryotes

fungi, protozoa, algae, helminths

viruses composition

DNA or RNA; protein coat; obligate intracellular parasites

viroids composition

RNA only; no protein coat; infect plants

prions composition

only misfolded proteins; cause spongiform encephalopathies; highly resistant to sterilization

how to distinguish a viroid from a virus

look for a protein coat

anton van leeuwenhoek

first to observe microbes; Father of Microbiology, Protozoology, and Bacteriology

who disproved spontaneous generation with swan-neck flask experiment

john pasteur

who discovered heat-resistant microbes and developed tyndallization

john tyndall

who discovered bacterial endospores

ferdinand cohn

who first proposed that invisible organisms cause disease

Girolamo Fracastoro

who proved anthraz is caused by bacillus anthraxis

Robert Koch

who proved TB is caused by mycobacterium tuberculosis

robert koch

spontaneous generation

belief that life arises from non-living matter

3 scientists that believed in spontaneous generation

van helmont, aristotle, john needham

scientists who opposed spontaneous generation

john tyndall, spallanzani, Redi, Pasteur

what did redi’s experiment show

Maggots only appear on meat when flies lay eggs; disproved spontaneous generation for larger organisms

what did needham’s experiment show

Boiled broth became cloudy with microbes ; falsely supported spontaneous generation (contamination occurred)

what did spallanzani’s experiment show

Boiled and sealed broth stayed clear;no spontaneous generation

what did Pasteur’s swan-neck experiment show

Broth remained sterile unless exposed to airborne dust;disproved spontaneous generation

why did some experiments still show growth even after boiling

because of endospores; discovered by ferdinand cohn

what is the germ theory of disease

idea that infectious diseases are caused by microorganisms

who proposed the germ theory

Louis Pasteur

what did robert koch contribute to germ theory

Proved specific microbes cause specific diseases; developed Koch’s Postulates

Koch’s postulates

1. Pathogen present in all diseased cases, absent in healthy.

2. Must be isolated in pure culture.

3. Pure culture causes disease in healthy host.

4. Same pathogen re-isolated from host

beneficial roles of microbes

Nitrogen fixation, oxygen production, nutrient cycling, decomposition, normal microbiota, food production, biodegradation, commercial products, research models

harmful roles of microbes

Cause food spoilage and disease (infectious and prion-related)

putrefaction

Protein breakdown in foods by proteolytic microbes; then produces amino acids, amines, ammonia, H₂S

fermentation

Carbohydrate breakdown in foods by fermenting microbes; then produces acids, alcohols, gases

rancidity

Fat breakdown in foods by lipolytic microbes; then produces fatty acids, glycerol, aldehydes, ketones

 Which microbial activity causes foul odor in spoiled meat

Putrefaction (due to ammonia and H₂S release)

Which type of spoilage is linked to souring and gas production

fermentation of carbohydrates

Which type of spoilage is responsible for the “off” smell and taste of spoiled butter or oils

rancidity from lipolytic microbes

If Pasteur’s broth contained endospores, what would his results have been? Why

Growth would have occurred despite boiling, because endospores are heat-resistant

A microbiologist has two samples: one virus and one viroid. What molecule should they look for to tell them apart

protein coat

why are prions difficult to eliminate

They are resistant to autoclaving and most sterilization methods; require proteolytic enzymes