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Microbiology Lecture > Chapter 2: A Brief Journey to the Microbial World > Flashcards

Chapter 2: A Brief Journey to the Microbial World Flashcards

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Biology 101 flashcards
1
Q

Bright-field scope

A

Specimens are visualized
because of differences in
contrast (density) between
specimen and surroundings

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2
Q

Objective lens and ocular lens calculation

A

• Total magnification = objective
magnification x ocular
magnification
• Maximum magnification is
~2,000x

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3
Q

Resolution:

A

– the ability to distinguish two adjacent
objects as separate and distinct
– Resolution is determined by the wavelength of light
used and numerical aperture of lens
– Limit of resolution for light microscope is about
0.2 u m

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4
Q

True or false: Improving contrast results in a better final image

A

True

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5
Q

Staining improves contrast

A

• Dyes are organic compounds that bind to specific cellular
materials
• Examples of common stains are methylene blue, safranin,
and crystal violet (basic dyes)

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6
Q

Bacteria can be divided into two
major groups:

A

gram-positive and
gram-negative

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7
Q

Differential stains: the Gram stain

A

Differential stains separate bacteria
into groups

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8
Q

Phase-Contrast Microscopy

A

• Invented in 1936 by Frits Zernike
• Phase ring amplifies differences in
the refractive index of cell and
surroundings
• Improves the contrast of a sample
without the use of a stain
• Allows for the visualization of live
samples
• Resulting image is dark cells on a
light background (Figure 2.5b)

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9
Q

Dark-Field Microscopy

A

• Light reaches the specimen from
the sides
• Light reaching the lens has been
scattered by specimen
• Image appears light on a dark
background (Figure 2.5c)
• Excellent for observing motility

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10
Q

Fluorescence Microscopy

A

• Used to visualize specimens that
fluoresce
• Emit light of one color when
illuminated with another color of light
• Cells fluoresce naturally
(autofluorescence) or after they
have been stained with a
fluorescent dye like DAPI
• Widely used in clinical diagnostic
microbiology, microbial ecology for
enumerating bacteria in natural
samples, or in cell suspension

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11
Q

Differential Interference Contrast
(DIC) Microscopy

A

• Uses a polarizer to create two
distinct beams of polarized light
• Gives structures such as
endospores, vacuoles, and granules
a three-dimensional appearance
(Figure 2.7a)
• Structures not visible using brightfield microscopy are sometimes
visible using DIC without staining

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12
Q

Atomic Force Microscopy (AFM)

A

• A tiny stylus is placed close to a
specimen
• The stylus measures weak repulsive
forces between it and the specimen
• A computer generates an image
based on the data received from
the stylus

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13
Q

Confocal Scanning Laser
Microscopy (CSLM)

A

• Uses a computerized microscope
coupled with a laser source to
generate a three-dimensional
image (Figure 2.8)
• Computer can focus the laser on
single layers of the specimen
• Different layers can then be
compiled for a three-dimensional
image
• Resolution is 0.1  m for CSLM

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14
Q

Electron Microscopy

A

• Electron microscopes use electrons
instead of photons to image cells and
structures
• Two types of electron microscopes:
• Transmission electron microscopes (TEM)
• Scanning electron microscopes (SEM)

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15
Q

Transmission Electron Microscopy
(TEM)

A

• Electromagnets function as lenses
• System operates in a vacuum
• High magnification and resolution
(0.2 nm)
• Enables visualization of structures
at the molecular level (Figure 2.10a
and b)
• Specimen must be very thin (20–60
nm) and be stained

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16
Q

Scanning Electron Microscopy
(SEM)

A

• Specimen is coated with a thin film
of heavy metal (e.g., gold)
• An electron beam scans the object
• Scattered electrons are collected by
a detector and an image is
produced (Figure 2.10c)
• Even very large specimens can be
observed
• Magnification range of 15–
100,000 but only the surface of an
object is visualized

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17
Q

All cells have the following in common:

A

• Cytoplasmic membrane
• Cytoplasm
• Ribosomes

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18
Q

Elements of Microbial Structure: Eukaryotes

A

• DNA enclosed in a membrane bound nucleus
• Cells are generally larger and more complex
• Contain organelles

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19
Q

Elements of Microbial Structure: Prokaryotes

A

No membrane-enclosed organelles, no nucleus

Generally smaller than eukaryotic cells

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20
Q

Viruses

A

• Not considered cells
• No metabolic abilities of their own
• Rely completely on biosynthetic
machinery of infected cell
• Infect all types of cells
• Smallest virus is 10 nm in diameter

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21
Q

Genome

A

A cell’s full complement of genes

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22
Q

Prokaryotic cells generally have a
single, circular DNA molecule called

A

chromosome

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23
Q

Plasmids

A

Prokaryotes also may have small
amounts of extra-chromosomal DNA
called plasmids that confer special
properties (e.g., antibiotic resistance)

24
Q

Eukaryotic DNA is linear and found within the nucleus

A

• Associated with proteins that help in folding of the DNA
• Usually more than one chromosome
• Typically two copies of each chromosome
• During cell division, nucleus divides by mitosis
• During sexual reproduction, the genome is halved by
meiosis

25
Q

Arrangement of DNA in Microbial Cells: Escherichia coli Genome

A

• 4.64 million base pairs
• 4,300 genes
• 1,900 different kinds of protein
• 2.4 million protein molecules

26
Q

Arrangement of DNA in Microbial Cells: Human Cell

A

• 1,000x more DNA per cell than E. coli
• 7x more genes than E. coli

27
Q

Evolution

A

The process of change over time that results in new varieties and species of organisms

28
Q

Phylogeny

A

• Evolutionary relationships between organisms
• Relationships can be deduced by comparing genetic information in the different specimens
• Ribosomal RNA (rRNA) is excellent for determining phylogeny
• Relationships visualized on a phylogenetic tree

29
Q

Comparative rRNA sequencing has defined three distinct lineages of cells called domains:

A

• Bacteria (prokaryotic)
• Archaea (prokaryotic)
• Eukarya (eukaryotic)

30
Q

Endosymbiosis

A

a term used to describe two organisms living together with one inside the other

31
Q

ancestors of multicellular organisms

A

eukaryotic microorganisms

32
Q

Metabolic Diversity

A

• The diversity in microbial cells is the product of
almost 4 billion years of evolution
• Microorganisms differ in size, shape, motility,
physiology, pathogenicity, etc.
• Microorganisms have exploited every conceivable
means of obtaining energy from the environment

33
Q

Chemoorganotrophs

A

• Obtain their energy from the
oxidation of organic molecules
• Aerobes use oxygen to obtain energy
• Anaerobes obtain energy in the
absence of oxygen

34
Q

Chemolithotrophs

A

• Obtain their energy from the
oxidation of inorganic molecules
• Process found only in prokaryotes

35
Q

Phototrophs

A

• Contain pigments that allow them to
use light as an energy source
• Oxygenic photosynthesis produces
oxygen
• Anoxygenic photosynthesis does not
produce oxygen

36
Q

All cells require ________ as a major nutrient

A

carbon

37
Q

Autotrophs use this as their carbon source

A

Carbon dioxide

38
Q

Sometimes referred to as primary producers

A

Autotrophs

39
Q

Heterotrophs

A

• Require one or more organic molecules for their carbon source
• Feed directly on autotrophs or live off products produced by
autotrophs

40
Q

extremophiles

A

organisms that inhabit extreme environments are
called

41
Q

Habitats of extremophiles

A

Habitats include boiling hot springs, glaciers, extremely salty bodies of water, and high-pH environments

42
Q

All known pathogenic
prokaryotes are

A

Bacteria

43
Q

Make up the largest phylum of Bacteria

A

Proteobacteria

44
Q

Gram-negative bacteria examples

A

E. coli, pseudomonas, salmonella

45
Q

Photosynthetic bacterias

A

Green sulfur and green nonsulfur bacteria

46
Q

Bacteria extremely resistant to radioactivity

A

Deinococcus

47
Q

Obligate intracellular parasites

A

Chlamydia

48
Q

Two Phyla of the Domain
Archaea

A

Euryarchaeota and crenarchaeota

49
Q

Euryarchaeota

A

• Methanogens: degrade organic
matter anaerobically, produce
methane (natural gas)
• Extreme halophiles: require high
salt concentrations for
metabolism and reproduction
• Thermoacidophiles: grow in
moderately high temperatures
and low-pH environments

50
Q

Crenarchaeota

A

• Vast majority of cultured Crenarchaeota are hyperthermophiles
• Some live in marine, freshwater,
and soil systems

51
Q

Ribosomal RNA are uses to infer evolutionary relationships between
organisms. Woese recognized genes encoding rRNA are:

A

(1) Universally distributed
(2) Functionally constant
(3) Highly conserved (slowly changing)
(4) Adequate length to provide a deep view of evolutionary relationships

52
Q

Eukaryotic microorganisms include

A

algae, fungi, protozoa, and slime
molds

53
Q

True or false: algae and protozoa are phototrophic

A

False

54
Q

Algae and fungi have _________,
whereas protozoa and slime molds do
not

A

cell walls

55
Q

mutualistic relationship
between two groups of protists

A

lichens

56
Q

Examples of lichens

A

• Fungi and cyanobacteria
• Fungi and algae

Microbiology Lecture (3 decks)

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