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Lecture 1

BIOL241 Lecture Notes - Lecture 1: Protozoa, Archaea, Central Dogma Of Molecular Biology

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Laura A Sauder

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Topic 1: Introduction to Microbiology
Microbiology is the science of microorganisms (very small, mostly unicellular
oThe discipline is just over a century old therefore it is a young,
vigorous and modern science
oHas given rise to molecular biology and biotechnology
oHas influenced almost every sector of human interest: health,
agriculture, food, and environment
oMicrobiology had an upheaval 20 years ago with the advent of
molecular techniques (i.e. the ability to sequence DNA and discover
new organisms) over the last century, we have just scratched the
Microorganisms vs. Macroorganisms
Traditionally, Prokaryotic = before a nucleus and Eukaryotic= possessing a
true nucleus (but some scientists dislike these terms)
Microorganisms are everywhere
oProduce greenhouse gases
oIn rice patty fields
oForests, hotsprings, etc.
oStromatolites are layers of microorganisms in biofilms that evolved
when the earth had no oxygen. They are photosynthesizers, so
they produce oxygen they grew in biofilms to protect them from
their oxygen—they give us oxygen
oOur microbes correlate to our health and almost all are beneficial
More microbial cells on Earth (1031) than there are starts in universe
Sextillion cells in the universe, nonillion bacterial cells on earth.
Microbial cells are far more abundant and interesting than starts

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Human cells= 10% human, 90% microbial
While one of the most important drivers for the development of the science of
microbiology was the recognition that many diseases are caused by
microorganisms, in reality, only a very small fraction of microorganisms cause
For most of the time that microorganisms have existed on earth, there were
no multicellular organisms to infect.
Physiological activities of microorganisms resulted in formation of a
“biosphere”, which allowed some of them to evolve into multicellular
Today, microorganisms comprise of over 50% of the Earth’s biomass and
most of these microorganisms are friendly to humans
Microorganisms have been very important model systems in the study of
biochemistry and genetics. Most of the fundamental biochemical and genetic
principles of life were developed through the study of microorganisms.
microbial cells can be cultured to high densities in the laboratory, facilitating
biochemical analysis, and they are easy to manipulate genetically
oContain DNA as the main informational macromolecule
oPossess a plasma membrane
oUtilize a similar genetic code
oContain ribosomes for protein synthesis
Although microbial cells do not differentiate into distinct tissues, as
multicellular organisms do, they do associate with other similar cells as:
oPopulations (single species)
oCommunities (multiple species)
Populations associate with other populations in communities
Interactions within microbial communities occur at several
levels, with waste products of some organisms provided as
nutrients for other organisms
In the process, the properties of a given ecosystem are often
Topic 1: The Microbial World
oThe study of microbes (things that are too small to see)
oExamines how microbes interact with humans, with food, and how
they can be used by humans
oInvolves the study of bacteria, archaea, and eukaryal
microorganisms (fungi, protozoa, algae) and viruses
oThe metabolic properties of microbes are related to their habitats
oStudies of microbes have provided insight into evolution of life and
oMicrobes remain important causes of disease throughout the world

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oMicrobe: everything microscopic (viruses, bacteria, archaea, micro
eukaryotes, etc.)
Not necessarily alive so viruses are included
Viruses are not living, but they use biological molecules and
borrow cellular machinery from their host to replicate and
can cause infectious diseases like some microorganisms
oMicroorganism: microbial life (bacteria, archaea, and eukaryotes)
Must be alive so viruses are excluded
Microscopic forms of life too small to see with the unaided
Usually consist of a single cell and include bacteria, archaea,
fungi, protozoa, and algae
Historical Roots of Microbiology
1. Robert Hooke (1635-1703)
Early microscopes allowed first description of microbes: fruiting
structures of moulds
He was interested in how things putrefy or mould
He looked at a mouldy piece of leather and saw fruiting bodies and
spores he hypothesized this correctly; however, he was never able to
see the spores or microbes because they were too small for his
He saw cells first
He saw fruiting bodies—not spores, archaea, bacteria, etc.
2. Antonie van Leeuwenhoek (1632-1723)
He is considered the father of microbiology
He built a much more powerful microscope than Hook and was able to
see bacteria swimming around
Microscope= metal plate with hole in the middle; he took a sphere of
glass and put in a hole and screw with a hip that you put a drop of
liquid in and hold it up to a bright light source
He called bacteria “animalcules” and estimated that there were more of
these in a drop of liquid than the number of men in his kingdom
“I then most always saw, with great wonder, that in the said matter
there were many very little animalcules, very prettily a-moving” –
Antonie van Leeuwenhoek
He scraped plaque off of old men who had never brushed their teeth,
then he looked at bodily fluid and saw sperm and red blood cells
Importance of Microbiology
Studies of microbes have provided insight into the evolution of life and
We can use light microscopes, epifluorescence microscopy and electron
microscopy (can see fine detail in cells)
Microbes can:
oCause disease
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