Unit 1

Who was Frederick Griffith, and what did he do and discover?

He was a British army doctor in WWI who studied the bacteria, Streptococcus pneumoniae, to figure out how bacteria caused diseases.

He discovered that the bacteria had two strains: S strain (smooth) and R strain (rough)

The smooth strain contained a polysaccharide capsule and was virulent. The rough strain did not contain a capsule and was avirulent. The capsule allows the virus to evade the host’s immune system

What happens when a smooth strain of Streptococcus pneumoniae is heat-killed?

It becomes avirulent.

What happens when a R strain of Streptococcus pneumoniae is mixed with a heat-killed S strain?

The R strain becomes virulent S strain.

Explain transformation (the “transforming principle”)

The ability for bacteria to acquire new traits by taking in new DNA from material in their environment.

What is a type of virus that infects E. coli?

Bacteriophage T2

Which bacteria is the most important model organism in biology and why?

E. coli

It has a small genome, rapid growth, and easily manipulated

Helps us study genes, evolution, recombinant DNA, and host-pathogen interactions

What discovery came out of Avery, MacLeod, and McCarty’s work?

They discovered that “nuclein” (DNA) was what allowed transformation to happen, not proteins, RNA, or polysaccharides.

What did the Hershey-Chase experiment prove, and how did they prove it?

By experimenting with bacteriophages, they observed that only the bacteriophage’s DNA entered the bacteria, and therefore must be the material that carries genetic information

Describe what a microbe is and how it relates to microbiology.

A microbe is a small living organism that cannot be seen by the naked eye. So, microbiology is the study of small living organisms.

What are the 5 classifications of microbes?

Bacteria, archaea, eukaryotic microbes, fungi, and viruses

What are three reasons why the definition for a microbe doesn’t quite fit all of the time?

1.) Supersized microbes exist (ex: Thiomargarita namibiensis)

2.) Are they all living organisms? Each microbe contains a genome and is able to reproduce

3.) There are microscopic non-microbes like worms and arthropods

What is the range in size of microbes?

0.2 micrometers to a few millimeters

How do the size of viruses compare to cells?

They are orders of magnitude smaller than even the smallest of cells

What is the viewing range for the human eye?

50 micrometers to 1 mm

What is the viewing range for light microscopy?

0.2 micrometers to 1mm

What is the viewing range for scanning electron microscopy?

All samples

What is the viewing range for transmission electron microscopy?

0.2 nm - 20 micrometers

How many micrometers in a nanometer

1000nm = 1 micrometer

Explain how Brightfield microscopy works and when to use it.

Visible light passes through the sample (staining is often needed) ; good for viewing whole cells/bacteria and larger microbes (0.2 micrometers and up)

Explain how Fluorescence microscopy works and when to use it.

Scientists use fluorescent dyes or proteins to make specific structures glow. Best for viewing particular cells, molecules, or dynamic processes (movement)

Good for viewing specific organelles

Explain how Electron microscopy works and when to use it.

Electron microscopy uses beams of electrons instead of light to achieve a higher resolution.

There are two types: TEM and SEM

TEM is best for viewing internal structures in a cell, and SEM is best for viewing the 3D surface of organisms

Essential for viruses and very small cellular structures

How do electrons give a higher resolution than light?

Resolution is limited by the wavelength of the beam. Smaller wavelengths lead to higher resolutions and finer details.

Visible light has wavelengths of about 400-700nm, while electrons, when accelerated, have wavelengths a fraction of that, which allows resolution of structures that are only a few nm

What are two reasons we care about taxonomy/classification/phylogenetic relationships?

1.) Helps create organizational structure and allows us to understand groups of microbes based on shared characteristics and shared ancestry

2.) Facilitates predictions and hypotheses about newly discovered species based on characteristics of the group

Explain what Linnaeus, Haeckel, and Whittaker discovered about microbe classifications.

Linnaeus → developed a new way to categorize plants and animals

Haeckel → recognized that microbes have separate kingdoms

Whittaker → distinguished prokaryotes and fungi (also prokaryotes vs. eukaryotes/ cellular differences)

What do all cells contain?

Cytoplasm, a genome, and ribosomes for protein synthesis

What are methanogens?

Microbes that produce methane

What is the Svedberg unit?

A measure of how fast a particle sediments when spun in an ultracentrifuge.

What does 30S and 16S belong to? Distinguish the two.

30S is the small subunit of a prokaryotic ribosome.

16S are the rRNA genes that code for the RNA portions in prokaryotic ribosomes

Why are ribosomes used to study ancestry in microbes?

Since 16S rRNA sequences are necessary for protein synthesis, they are present in distantly related prokaryotes and modern ones.

The gene is functionally constrained, so there are low rates of evolution in this gene.

The 16S rRNA interacts with many ribosomal proteins, and it is incompatible in species that it does not belong to (resistant to movement across species; one for one group = unique)

What is “molecular fingerprinting” of rRNA?

1.) Scientists cut the RNA into short fragments that contain only a few nucleotides

2.) They separate the fragments using electrophoresis

3.) They sequence the short fragments using radioactive labeling to build a catalog of fragments for each microbe

How is molecular fingerprinting useful for studying microbes?

Allows scientists to look between species and compare fragment sizes between microbes.

What are the 3 domains of life?

Archae, bacteria, and eukaryotes

Between eukaryotes, archaea, and bacteria, which two share the most recent common ancestor?

Eukaryotes and archaea

Which two domains of life occurred approximately around the same time? Which occurred last?

Bacteria and archaea arrived at around the same time, whereas eukaryotes came last from a common ancestor with Archaea

rRNA analysis provided a ______ taxonomy, revealing the three fundamental domains of life

molecular

List the order from earliest to most recent in arrival:

*phototropic microorganisms (cyanobacteria, multicellular life, eukaroytes)

*microbes capable of anaerobic metabolism

*bacteria and archaea

1.) Microbes capable of anaerobic metabolism because of the anoxic atmosphere

2.) Bacteria and archaea

3.) Cyanobacteria (oxygen-producing microbes) after phototropic microorganisms helped start the transition to an oxygenated atmosphere

3.) Multicellular life after oxygenation

4.) Eukaryotes

How many microbial cells are estimated to be on Earth?

2 × 10 ^ 30

Where in our bodies are methanogenic archaea common?

In the mammalian gut