Millimeter (mm)
10^-3 m (1000 mm in a m)
Micrometer (µm)
10^-6 m (1000 µm in a mm)
Previous
Play
Next
Rewind 10 seconds
Move forward 10 seconds
Unmute
0:03
/
0:15
Full screen
Brainpower
Read More
Nanometer (nm)
10^-9 m (1000 nm in a µm)
Microbes
Organisms and ace...
Millimeter (mm)
10^-3 m (1000 mm in a m)
Micrometer (µm)
10^-6 m (1000 µm in a mm)
Previous
Play
Next
Rewind 10 seconds
Move forward 10 seconds
Unmute
0:00
/
0:15
Full screen
Brainpower
Read More
Nanometer (nm)
10^-9 m (1000 nm in a µm)
Microbes
Organisms and acellular agents too small to be seen by the unaided eye
~100-200 µm
What is the limit of detection for the unaided eye?
10,000 µm
What is the width of a fingernail?
2 µm
What is the length of Escherichia coli (E. coli)?
0.2 µm
What is the length of T4 phage (virus that infects bacteria)?
There are 1000 nm in 1 µm so 2 µm is equivalent to 2000 nm. Both cells are the same
sisze.
You have an E. coli bacterial cell that is 2 µm and a Salmonella bacterial cell that is
2000 nm. Which cell is larger?
, Microbial size contradictions
1. Supersize microbial cells: outliers we can sometimes see (ex: Thiomargarita
namibiensis is 0.7 mm or larger, some giant amoebas can be seen by unaided eye)
2. Microbial communities: in some cases we can see (ex: mushrooms easily seen
with unaided eye)
3. Viruses: considered acellular agents, not living; microorganisms but not cells...just
nucleic acid surrounded by protein coat
Robert Hooke (1635-1703)
-Built the first compound microscope
-Used it to observe mold, fleas, cork: looking at world in new way, could see details of
animals, plants, soil
-Published Micrographia: intricate drawings of what he saw, believe now may have
been fungus
-Coined the term "cell"
-First scientist credited with describing microorganism at cellular level
Antonie von Leeuwenhoek (1632-1723)
-Built single-lens magnifiers
-First to observe single-celled microbes: "discovered" bacteria (published drawings and
descriptions)
-He called them "small animals": "animolecules" (had no point of reference)
Spontaneous generation
The controversial theory of living organisms from non-living matter (life will
spontaneously arise from non-living) debated by many historical scientists
-Decaying meat "produced" maggots
-Sand "produced" oysters and clams
-Used as evidence for microorganisms but many disagreed
Francesco Redi (1626-1697)
Showed that maggots on decaying meat came from fly eggs deposited on the meat, not
from the meat itself
-Published that this refuted spontaneous generation
-Life (maggots) came from other life (flies), further analysis showed microscopic life
associated with decaying meat but couldn't be explained at the time
Lazzaro Spallanzani (1729-1799)
Showed that nutrient broth sealed in flasks and then boiled had no growth of
microorganisms
-Disproved spontaneous generation; microbial life must be coming from outside
container, not non-living broth
-Conclusions: cellular fission of microbes in broth...showed microbes do have "parents"
Louis Pasteur (1822-1895)
Showed that nutrient broth heated in swan neck flasks had no growth of
microorganisms, but broken necked flasks did
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller tuition. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.99. You're not tied to anything after your purchase.
