Chapter 1: Humans & The Microbial World

Microorganism

a microscopic organism, especially a bacterium, virus, or fungus

Microbes

a microorganism, especially a bacterium, causing disease or fermentation

Biogenesis

Theory that life comes from previous life

Endospores

a heat-resistant asexual spore that develops inside some bacterial cells

Germ Theory of Disease

The principle that microorganisms cause diseases

Spontaneous Generation

The discredited belief that organisms can arise from non-living matter

Francesco Redi

Wanted to prove that worms found on rotten meat originated from fly eggs, not spontaneous generation.

Experiment: Put meat in a jar with one jar open, one jar sealed with gauze, and one jar sealed with a lid.

Conclusion: He disproved spontaneous generation, but it was not accepted till 200+ yrs.

John Needham

Experiment: Broths in a flask that was sealed to see if organisms would not grow if boiled (at that time, boiling was used to sterilize).

Conclusion: That boiling would sterilize all the microorganisms, proving spontaneous generation

Lazzaro Spallanzani

Experiment: Similar to Needham’s experiment, but differs by boiling the broth for a longer period of time, and he sealed the glass by melting the glass neck closed.

Conclusion: The flasks remained sterile free of microorganisms, but if the glass broke, then the microorganisms would enter. Leading to air affecting the growth of microorganisms.

Louis Pasteur

Experiment: Used swan-neck flasks and boiled the broth to demonstrate the effect air has on microorganisms, and filtered the air through a cotton plug.

Conclusion: If the flask was right side up, the air was able to escape, and there would be no microorganism growth, but when the flask was tilted so that air could reach the microorganisms, they grew.

John Tyndall

Proved that Pasteur’s theory was correct. That broth from some hay can contain living microorganisms after boiling, and these hay contained heat-resistant forms

Conclusion: Microorganisms exist in 2 forms

1. A cell is easily killed by boiling

2. A heat-resistant cell

Ferdinand Cohn

Discovered a heat-resistant form of bacteria called endospores

Normal Microbiota

The human body’s enormous population of microorganisms

Microbiome

total genetic content of the microbial community

Biodegration

degrade environmental pollutants

food production

deration of toxic pollutants

used bacteria to synthesize commercially valuable products

What are some examples of commercial benefits of microorganisms?

Bioremediation

Use of microorganisms to hasten the decay of pollutants

Pathogens

Disease-causing microbe

Emerging Infectious Disease (EID)

an infectious disease that has become more widespread in the last several decades

Prokaryotic Cell

cell type with a lack of membrane-bound nucleus

Eukaryotic Cell

cell type with a membrane-bound nucleus

Eukaryote

An organism composed of 1 or more eukaryotic cells

Prokaryote

single-cell organism no nucleus

Domain

Highest level in the biological classification

Genus

taxonomic category of related organisms, usually containing several species

Species

a group of closely related strains; basic unit of taxonomy

Strain

pure culture isolate; genetic variant within a species

Coccus

Sphere shaped bacteria

Bacillus

Rod shaped bacteria

Vibrio

Short curved, rod shaped bacteria

Spirillum

curved rod long enough to form spirals shaped bacteria

Spirochete

long spiral with flexible, shaped wall bacteria

Diplococci

Cocci that remains as pairs

Strepto

twisted chains of cocci

Cubical Packets

Cocci that divide in perpendicular planes

Grape-Like Clusters

Cocci that divide randomly in several planes may form

Staphylo

“Bunch of Grapes”

Bacteria

single celled prokaryotes

Archaea

Eukarya

unicellular of multicellular Eukaryotes

Fungi

Diverse group ranging from single-cell yeast to multicellular filamentous molds

Conidia

filamentous mold that spreads by the invisible mat called mycelium

Algae

Diverse group of photosynthetic Eukaryotes

Protozoa

Diverse group of single-celled Eukaryotes

Helminths

Parasitic worms

Viroid

an infectious agent of plants that consists only of RNA

Virus

an acellular infectious agent consisting of nucleic acid surrounded by a protein coat

Prions

an infectious protein that causes a neurodegenerative disease