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MBIO 1010 > Microbiology and Microorganisms > Flashcards

Microbiology and Microorganisms Flashcards

1
Q

What is Microbiology?

A
  • The study of organisms too small to be seen with the naked eye. (Bacteria, Viruses, Single celled eukaryotes).
  • Some microorganisms are visible to the naked eye. (Fungi, Algae)
  • Some microbes are multicellular. (Myxobacteria, slime molds)
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2
Q

What is Microbiology? (2)

A

Microbiology is defined by techniques
- culture media for isolation and growth of organisms in pure culture
- Biochemical to study cell components
- Molecular and genetic techniques

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3
Q

Why is Microbiology Important?

A
  • Microbes are the oldest form of life
  • Largest mass of living material on Earth
  • Carry out major processes for biogeochemical cycles
  • Can live in places unsuitable for other organisms
  • Other life forms require microbes to survive
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4
Q

Structure and Activities of Microbial Cells

A

All cells have the following in common:
- Cytoplasmic membrane (Barrier that separates the inside of the cell from the outside environment)
- Cytoplasm (Aqueous mixture of macromolecules, ions, and proteins)
- Ribosomes (Site of protein synthesis)

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5
Q

Structure and Activities of Microbial Cells (part 2 )

A
  • Genetic material
    (All cells store their genetic information as DNA, The information is divided into functional units called genes)
  • Genome
    (A cell’s full complement of genes)
  • Chromosome
    (A genetic element carrying genes essential to cellular function)
  • Plasmid
    (A piece of DNA that carries non-essential genes (ex. Genes for antibiotic resistance, genes for nitrogen fixation, etc)
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6
Q

Structural Categorization of Microbes (Eukaryotes)

A
  • Membrane bound nucleus
  • Membrane bound organelles
  • Complex internal organization
  • Division by mitosis and meiosis
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7
Q

Major Groups of Eukaryotic Microbes

A

Protists - unicellular or multi-cellular without differentiation into tissues
Fungi - Unicellular (yeast), filamentous (molds), or multi-cellular (mushrooms)

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8
Q

Protists

A

Protozoa - animal-like microorganisms
Algae - photosynthetic plant-like microorganisms
Slime molds and water molds - filamentous

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9
Q

Structural Categorization of Microbes (Prokaryotes)

A
  • No membrane bound nucleus or organelles
  • Generally smaller (approx 1 m diameter
  • Simple internal structure
    -Divide by binary fission
  • Most are unicellular
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10
Q

Major Groups of Prokaryotic Microbes

A
  • Bacteria (eubacteria)
  • Archaea (archaebacteria)
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11
Q

Bacteria (eubacteria)

A
  • Genetically diverse
  • Extremely diverse metabolic styles
  • Includes both pathogens and non-pathogens
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12
Q

Archaea (archaebacteria)

A
  • Genetically and biochemically distinct from bacteria
  • Also have diverse metabolism
  • Never pathogenic
  • Most famous for living in extreme environments
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13
Q

Structural Categorization of Microbes (Viruses)

A
  • Acellular infectious particles
  • Extremely small
  • Obligate intracellular parasites
  • Lack indenpendent metabolism
    • No ribosomes
    • No ribosomal RNA,
    • Cannot be classified with other microbes
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14
Q

Evolution and Diversity of Microbial Cells

A
  • First anaerobic life appeared between 3.8 and 3.9 billion years ago
  • Photosynthetic bacteria oxygenated the Earth about 2 billion years ago. (Allowed the evolution of modern eukaryotic microorganisms)
  • First plants and animals appeared about 0.5 billion years ago
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15
Q

Classifying Organisms Based on Evolutionary Relationships

A
  • Comparing small subunit (SSU) rRNA genes
  • Prokaryotes - 70S ribosomes (16S SSU rRNA)
  • Eukaryotes - 80S ribosomes (18S SSU rRNA)
  • rRNA genes change slowly over time
  • Examines genetic differences rather than morphological differences
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16
Q

Basic steps involved in sequencing rRNA genes

A
  • Step 1: DNA is collected from a pure culture
  • Step 2: The SSU rRNA gene is amplified using the polymerase chain
    reaction (PCR)
    - PCR – a technique used to synthesize many identical copies of a short sequence
    of DNA
  • Step 3: The gene is sequenced
  • Step 4: Sequence is aligned with sequences from other organisms
    - Number of differences is used to calculate evolutionary distance
17
Q

Phylogenetic tree

A

A graphic representation of the evolutionary distance
between organisms.

18
Q

Molecular Phylogeny and the Tree of Life

A
  • Phylogenetic tree based on 16S or 18S ribosomal DNA sequences
  • All organisms can be grouped into 3 distinct domains of life: Bacteria,
    Archaea and Eukarya
  • Microorganisms are far more genetically diverse than plants and
    animal
19
Q

what is a species?

A
  • Phylogenetic species concept:
  • “A group of strains that share certain diagnostic traits, are genetically cohesive and have a unique recent common ancestor”
20
Q

What should species of Bacteria and Archaea have?

A
  • Most (but not all) characteristics in common
  • Greater than 97% sequence similarity in the 16S rRNA gene
  • High degree of genome similarity
  • DNA-DNA hybridization
  • In the very near future: whole genome sequences?
21
Q

Classification and Nomenclature

A
  • Microbiologists use Hierarchical classification
  • Groups of organisms are placed in successively larger groups
  • In practice: Species, genus and phylum are commonly used
22
Q

Binomial species names Rules

A
  1. Names are latinized
  2. Italicized or underlined
  3. Genus capitalized, epithet is not
  4. Genus name may be abbreviated the second time it’s used: E. coli
  5. Trivial names can be used, but do not follow these rules
    Genus (Capitalized) Specific epithet (not capitalized) Strains (symbols at the end)
23
Q

The Discovery of Microorganisms (Robert Hooke)

A

1635 - 1703
- the first to describe microbes.
- Used a compound microscope - uses 2 lenses to magnify the image.
- allowed magnification up to 30x
- Used it to observe:
- cells in cork
- Bread mold filaments - 1st microbe
- Beginning of cell theory - all living things are composed of cells

24
Q

The Discovery of Microorganisms (Antoni van Leeuwenhoek)

A

1632 - 1723
- built microscopes that magnified specimen by 50-300x
- Observed single celled microorganisms - called them “animalcules”
- First discovery of bacteria

25
Q

Louis Pasteur (1822 - 1895)

A
  • Studied wine and beer production.
  • Yeasts convert sugar to alcohol in the absence of oxygen
    • Fermentation - “La vie sans air”
  • bacteria can sour wine by converting alcohols to acid
  • Developed a method of gentle heating to kill unwanted bacteria - Pasteurization
26
Q

Louis Pasteur (1822 - 1895) Continued

A
  • Prepared meat infusions inside of long swan-necked flasks.
  • Boiled the infusion to sterilize it.
  • As long as the flask remains upright, dust and microbes cannot enter, and the infusion remains sterile
    - Led to the development of methods for controlling the growth of microorganisms (aseptic technique)
27
Q

Koch, Infectious Disease, and Pure Cultures

A
  • Realized that solid media provided a simple way to obtain pure cultures
  • Broth medium solidified with agar
    • Polysaccharide derived from marine algae
    • Melts at ~ 97°C and polymerizes (solidifies) at ~ 43°C
    • Cannot be degraded by most microorganisms
    • Typical Petri plate = nutrient broth medium + 1.5% agar
28
Q

Robert Koch (1843 - 1910)

A

Studied anthrax – responsible for epidemics in livestock
- He isolated bacteria from the carcass of a diseased animal – Bacillus anthracis
- Injected healthy animals with the bacterium
- Animals became ill with anthrax
- Re-isolated B. anthracis from the test subjects and showed that it was identical
- Established a set of criteria for relating a specific microbe to a disease
- Koch’s postulates

29
Q

How to create Pure Culture?

A

The streak plate technique
- One edge of a plate is inoculated with a
concentrated sample of bacteria
- Sample is diluted by streaking it across the
surface of the plate
- To deposit individual cells on the plate (separate
from other cells)
- Plate is incubated
- Individual cells grow to form colonies

30
Q

Colony?

A

A mass of cells that (ideally) arose from one single cell
- Can be used to create a pure culture

31
Q

The Spread Plate and Pour Plate Techniques

A
  • Sample is diluted before plating
  • Diluted sample can be spread over the surface of the plate with a sterile spreader
  • Separate cells grow into colonies on the surface of the plate
  • Or can be mixed with molten agar (~ 45°C)
  • Colonies form embedded inside the plate
32
Q

The Standard Plate Count

A

Spread and pour plates allow you to calculate the concentration of bacteria in a population (Bacterial titre)
- titre = # colonies / (volume) (dilution)
- titre is expressed in cfu/ml
- cfu = colony forming unit

33
Q

Countable Plates

A

We normally count plates with between 30 – 300 colonies
- < 30 – not statistically significant
- > 300 – colonies grow into each other – inaccurate counts
- When we have more than one countable plate…
- Calculate titre from each and take the average.

MBIO 1010 (13 decks)

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