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Veterinary Bacteriology and Mycology > Bacterial Structures and Their Functions > Flashcards

Bacterial Structures and Their Functions Flashcards

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1
Q

illumination is provided by what in the case of brightfield microscopy

A

visible light

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2
Q

What is the resolving power of brightfield microscopy

A

0.2 um

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3
Q

what are the principal uses of brightfield microscopy

A

observation of stained specimens, etc.

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4
Q

describe the path of light through a compound light microscope

A

illuminator -> condenser lenses -> specimen -> objective lenses -> prism -> ocular lens -> line of vision

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5
Q

what does a light microscope use to magnify objects

A

ordinary light

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6
Q

what are the two types of lenses in a light microscope

A
  1. ocular/eyepiece (10x magnification)
  2. objectives (4x, 10x, and 40x magnification)
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7
Q

what are the objects seen through a light microscope measured in

A

micrometers (um) where 1000 um = 1 mm

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8
Q

what is a phase-contrast microscope

A

a special type of light microscope that increases differences in light and dark areas; primarily used in biological and medical research

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9
Q

How does a phase-contrast microscope work

A

enhances contrast of transparent and colorless specimens without the use of stains

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10
Q

what is a stereoscope

A

has two sets of lenses for each eye that enables you to see the object in its true 3D form

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11
Q

describe the magnification in a stereoscope

A

2 eye pieces with matching objectives for each eye; magnification ranges between 3x and 50x (like a high powered magnifying glass

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12
Q

electron microscopy uses ______________ rather than visible light

A

beams of electrons

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13
Q

electron microscopy has a greater resolving power because of what

A

wavelengths of electrons are approximately 100,000 times smaller than the wavelengths of visible light

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14
Q

what are the principal uses of electron microscopy

A

used to observe structures too small to be resolved by light microscopes such as fimbriae and viruses

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15
Q

what are the 2 types of electron microscopes

A

scanning electron microscope and transmission electron microscope

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16
Q

describe how acidic and basic stains stain cations and anions

A

Acidic: cations are colorless and anions are colored

basic: cations are colored and anions are colorless

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17
Q

how do you prepare a gram stain on a slide

A
  • spread culture in a thin film over the slide
  • air dry
  • pass slide through flame to heat fix
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18
Q

in what order are the gram stains used

A
  1. application of crystal violet (purple dye)
  2. application of iodine (mordant)
  3. alcohol wash (decolorization)
  4. application of safranin (counterstain)
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19
Q

what are the colors associated with gram reactions

A

purple: gram positive

pink: gram negative

mixed pink and purple: will see both colors on the slide

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20
Q

what is the significance of a gram reaction

A
  • identification of pathogen
  • selection of antibacterial agents
  • clinical evaluation of a disease
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21
Q

what is endotoxemia

A

develops after infection with a gram-negative bacteria; they produce an endotoxin when they die which leads to sepsis, septic shock, and death

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22
Q

what does coccus refer to

A

sphere-shaped bacteria
- coccus: 1
- diplococci: 2 fused

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23
Q

what do the prefixes strepto- and staphylo- refer to with cocci

A

streptococcus is a line formation of cocci

staphylococcus is a cluster formation of cocci

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24
Q

what does tetrad mean when referring to cocci

A

a plane of 4 cocci

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25
what does sarcinae refer to when referring to cocci
a cube formation; two tetrads stacked on top of one another
26
what does the term bacillis refer to
a rod-shaped bacteria - bacillus: 1 - diplobacilli: 2 fused
27
what do the prefixes strepto- and cocco- refer to with bacillus
streptobacillus: line formation of bacilli coccobacillus: clusters of bacilli
28
what are the different terms used for spiral-shaped bacteria
- vibrio: one hump - spirillum: two or more humps
29
what is a spirochete
an elongated spirillum bacteria
30
true or false: all bacteria have a capsule
false ## Footnote Bacteria without a capsule, or non-capsultated bacteria, include Neisseria, Corynebacterium, Salmonella, Shigella, Vibrio, Proteus, Pseudomonas
31
do all bacteria have flagellum
no
32
what do the external layers outside of the cell wall of a bacterial cell include
- surface protein (fibronectin) which act as adhesions and facilitate tissue colonization - capsule: gelatinous layer that covers the entire bacterium
33
what is the bacterial capsule composed of
polysaccharide, except in the anthrax bacillus, which has a capsule of polymerized D-glutamic acid
34
what do the sugar components of the polysaccharide capsule of a bacterium determine
the serologic type within a species; can vary from one species of bacteria to another
35
what is the function of a bacterial capsule
protects the bacteria form phagocytosis
36
what is the bacterial glycocalyx
loose network of polysaccharide fibrils that surround some cell walls and are associated with adhesive properties and contain prominent antigenic sites
37
how can you see the capsule of a bacterium on microscopy
it stains negatively
38
how does the presence of a capsule in bacteria relate to its ability to cause disease
if a bacterium has a capsule, it is more able to cause disease than one without a capsule
39
what are flagella
polymerized flagellin proteins; long, whip-like, and move bacteria towards nutrients and other attractants and contain prominent antigenic determinants
40
what are the two types of flagella
polar or peritrichous
41
what does monotrichous mean
an organism with a single flagellum
42
what does lophotrichous mean
an organism with multiple flagella arising from the same point on the cell
43
what does amphitrichous mean
an organism with a single flagella on either end
44
what does peritrichous mean
an organism with multiple flagella distributed all over the body
45
how do you test if an organism is motile or not
semisolid agar (motility agar): stab the agar with an inoculated stick and see if the organisms travel through the agar as they grow and multiply
46
what are pili (fimbriae)
pillin proteins arranged in helical strands that appear as hair-like filaments that extend from the cell surface
47
how are pili different from flagella
shorter, straighter, and more rigid than flagella
48
on what organisms are pili most commonly found
gram negative organisms
49
what are the different types of pili
- ordinary pili for adhesion - sex pili for attachment to F minus and transfer of genetic material during conjugation
50
what is another function of pili outside of adhesion and reproduction
also function as virulence factors and have antiphagocytic properties
51
what are the characteristics of the cell wall
- multi-layered - located external to the cytoplasmic membrane
52
what does the cell wall consist of
- inner layer of peptidoglycan - outer membrane (gram negative only) and varies in thickness and composition depending on the bacterial type
53
what does peptidoglycan do in the cell wall
structural support and maintenance of characteristic shape of the cell
54
which type of bacteria has a thicker layer of peptidoglycan and teichoic acid
gram positive
55
what is lipopolysaccharide (LPS)
an endotoxin found in gram negative cell walls
56
what are the components of the cell wall of gram negative bacteria
- complex outer layer - periplasmic space - endotoxin, a lipopolysaccharide -porin proteins in the outer membrane
57
what is the complex outer wall of the cell wall of gram negative bacteria composed of
LPS, lipoprotein, and phospholipid
58
what is contained within the periplasmic space of some species
enzymes called beta-lactamases that degrade penicillins and other beta-lactam drugs
59
what do the porin proteins in the outer membrane allow for
acts as a channel to allow the entry of essential substances such as sugars, amino acids, vitamins, and metals, as well as many antimicrobial drugs such as penicillins
60
what are the components of LPS
- O-specific polysaccharide - core polysaccharide - lipid A
61
what happens to organisms when they lose their cell wall
they are subjected to osmotic pressures
62
why is peptidoglycan a good target for antibacterial drugs
it is present in bacteria but not in animal cells
63
how do drugs like penicillins and cephalosporins inhibit the synthesis of peptidoglycan
inhibiting the transpeptidase that makes the cross-links between the two adjacent tetrapeptides
64
what is the difference between the peptidoglycan layer of gram positive and gram negative bacteria
gram +: thick and multilayered gram -: thin
65
what is the difference between the presence of teichoic acids of gram positive and gram negative bacteria
gram +: often present gram -: absent
66
what is the difference between the presence of the outer membrane of gram positive and gram negative bacteria
gram +: absent gram -: present
67
what is the difference between the presence of endotoxin of gram positive and gram negative bacteria
gram +: absent gram -: present
68
what is the difference between the lysozyme sensitization of gram positive and gram negative bacteria
gram +: sensitive gram -: resistant
69
what is the difference between the susceptibility to penicillin of gram positive and gram negative bacteria
gram +: yes gram -: no
70
do both gram + and gram - bacteria participate in complement activation and opsonization
yes
71
do both gram + and gram - bacteria participate in membrane lysis by MAC
no, only gram -
72
which type of bacteria (gram + or gram -) participate in spore formation
gram +
73
describe the cell wall of mycobacteria (Mycobacterium tuberculosis) with respect to staining
- unusual cell wall that cannot be gram-stained - said to be acid-fast because they resist decolorization with acid alcohol after being stained with carbolfuschin - property is related to the high concentration in the cell wall of lipids called mycolic acids
74
where is lysozyme found
in human tears, mucus, and saliva
75
what is the function of lysozyme
it can cleave the peptidoglycan backbone by breaking its glycosyl bonds and contributes to the natural resistance of the host to microbial infection
76
what is LPS
component of the outer membrane of the cell wall of gram - bacteria that is an endotoxin and is responsible for many features of disease such as fever and shock, especially hypotension
77
why is LPS called an endotoxin
it is an integral part of the cell wall, as opposed to exotoxins, which are freely released from the bacteria
78
what stain is used for mycolic acids
Zeil-Neelson stain (Z-N stain): acid fast; want to steam the slide first in order to melt the fat
79
where is the plasma membrane located
just inside the peptidoglycan layer of the cell wall
80
what is the cell membrane composed of
phospholipid bilayer similar in microscoping appearance to that in eukaryotic cells
81
how are the plasma membranes of prokaryotic vs eukaryotic cells different
chemically similar except for the eukaryotes contain sterols, and prokaryotes generally do not
82
what is the only prokaryotes that have sterols in their cell membrane
members of the genus Mycoplasma (they have no cell wall)
83
what is the function of ribosomes
protein synthesis; composed of 50S and 30S components
84
what is the endospore
tough dormant structure that some bacteria are able to form when stressed
85
describe the different arrangements of endospores
can be spherical or oval-shaped and can be central, subterminal, or terminal (usually bulging); all in gram + bacteria
86
what are the 2 genera of gram + bacteria that usually form spores
- bacillus - clostridium
87
cells are differentiated after what step of the gram stain
alcohol-acetone

Veterinary Bacteriology and Mycology (8 decks)

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