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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5579_Библиотеки_им_академика_М_И_Перельмана.pdf
occur due to the biogenesis process. He experimented as
follows :
He took a vessel in which nutrient medium is filled then
heated with a flame and then exposed to air but a filter
paper is bind on the neck of the vessels which prevent all
particles from passing through to the growth medium.
Nothing grew in the broths.
In the next experiment when all the above conditions
were kept the same except flasks were open, not
covered by any covering show microorganism growth
in the flask. He proposed that living organisms
that grew in broths came from outside rather than
spontaneously generated within the broth.
Germ theory of disease: Germ theory states that
many diseases are caused by the invasion of specific
microorganisms into the body. Proposed by Louis Pasteur,
Joseph Lister, and Robert Koch.
Contribution of Leeuwenhoek, Robert Koch, Jenner,
Louis Pasteur and Ehrlich Louis Pasteur (1822–1895):
Father of microbiology
Give germ theory of disease: Demonstrate that
microorganism (present in the environment) produces
disease rather than the air itself which is also known as
Miasma theory).
Rejected theory of spontaneous generation of
microorganism.
Showed microbes are responsible for causing fermentation
and spoilage of food.
Producing the first vaccine for rabies and anthrax.
Invented pasteurisation an explanation of and sterilisation
methods.
Give explanation on fermentation theory.
Antony Van Leeuwenhoek
Observed living microbes first time.
Used shis homemade microscopes to examine microorganisms in rainwater, well water, seawater and water.
He described his findings through writing of series of papers
describing bacteria, algae, protozoa, and fungi.
Described parasitic protozoan first time.
Robert Koch (1843–1910): Founder of modern bacteriology.
Gave statement that “life’s smallest structural units
were cells”.
Identified bacterial pathogens first time.
Gave methodology for counting microbes.
Developed pure culture techniques.
Awarded by Nobel Prize in 1905 for his significant
contribution in the development of magic bullets.
Succeed to separate out anthrax bacillus, tuberculosis,
and Vibrio cholerae.
Proved that anthrax is caused by bacillus anthracis
(bacteria).
Koch with his team developed methods of bacterial
staining.
Edward Jenner (1749–1823): Father of immunology
Vaccinated first time a boy named James Phipps against
smallpox in 1798.
Hypothesised that exposure to cowpox somehow led to
protection against smallpox.
In order to prove his point, he inoculated James Phipps
first with cowpox material, and later with smallpoxcausing material. The boy did not get smallpox.
Paul Ehrlich (1854–1915)
Paul Ehrlich (1909) discovered a synthetic arsenic
compound named Salvarsan that proved effective
against syphilis bacterium.
Applied stains to cells and tissues for the purpose of
revealing their function.
Introduced methods of standardising toxin and antitoxin.
Proposed side-chain theory of antibody production.
He created a new branch of medicine known as
chemotherapy.
2. Microscopy
Light compound microscope
It has subjective and objective lenses which help to
enlarge the size of the object.
Objective lens kept near to object to being observed.
The ocular lens or eyepiece lens, through which the
image is seen by the eye.
When a tiny object to be magnified is placed just beyond
the focus of its objective lens, a virtual, inverted and
highly magnified image of the object is formed at the
least distance of distinct vision from the eye held close
to the eyepiece.
A beam of visible light from the base is focused by a
condenser lens onto the specimen. The objective lens
picks up the light transmitted by the specimen and
produces a magnified ‘real image’ first image of the
object. This image is again magnified by the ocular
lens (eyepiece) to obtain a magnified ‘virtual image’
(final image), which can be seen by the eye through
the eyepiece.
Parts of the compound microscope
1. Structural components: Compound microscope has
three basic, structural components as follows:
A. Body houses the optical parts in the upper part of the
microscope.
B. Base: It supports the microscope and houses the
illuminator.
C. Arm: It is held base at one end and the microscope head
at another end. It is also used to carry the microscope
from one place to another.
Section 5 Microbiology
459458
2. Optical components: It can be divided into two parts
as eyepiece lens and objective lens.
A. Eyepiece or ocular is present on the top of the
microscope through which you can see the object under
study. Typically, standard eyepieces have a magnifying
power of 10X and 15X. Optional eyepieces of varying
powers are available, typically from 5X–30X.
B. Eyepiece tube: Holds the eyepiece in place above the
objective lens. Binocular microscope heads typically
incorporate a diopter adjustment ring which is used
for possible inconsistencies of eyesight in one or both
eyes. The monocular microscope does not need a diopter
adjustment ring.
C. Objective lenses are the primary optical lenses on a
microscope. Their power ranges from 4X–100X and
typically, include, three, four or five lenses on most
microscopes. Objectives can be forward or rear-facing.
D. Nosepiece carries the objective lenses on a rotating
turret. The objectives are exposed and are mounted
on a rotating turret so that different objectives can be
conveniently moved and then selected as required.
Standard objectives include 4X, 10X, 40X and 100X
although different power objectives are available.
E. Coarse and fine focus knobs are used to focus the object
under study. Increasingly, they are coaxial knobs —that
means they are built on the same axis with the fine focus
knob on the outside. Coaxial focus knobs are more
convenient to use.
F. Stage: It is flat in the surface where the specimen to
be viewed is placed. A mechanical stage is used when
working at higher magnifications where delicate
movements of the specimen slide are required in the
proper place.
G. Stage clips are required to move the slide manually to
view different sections of the specimen.
H. Aperture is a small hole in the stage through which the
base (transmitted) light hit the stage.
I. Illuminator/mirror is the light source for a microscope,
typically located in the base of the microscope. It reflects
the light from the outside source from the bottom of the
stage.
J. Condenser is used to collect and focus the light from
the illuminator and control the amount of light that
reaches the specimen. It is located under the stage often
in conjunction with an iris diaphragm.
K. Iris diaphragm controls the amount of light reaching the
specimen. It is located above the condenser and below
the stage. It is used to vary the intensity and amount of
light that is projected upward into the slide under the
study.
L. Condenser focus knob moves the condenser up or down
to control the lighting focus on the specimen.
M. There are three types of condensers used in the
compound microscope as follows (Fig. 2.1):
Section 5 Microbiology
(a) Abbe condenser: Numerical aperture = 1.25
(b) Variable focus condenser: Numerical aperture = 1.25
(c) Achromatic condenser: Numerical aperture = 1.40
Fig. 2.1: A compound microscope
Resolving Power of Objective
It is a property of the objective lens to resolve each point
on the object into widespread points so that the points in
the image can be seen as clear and separated from one another.
Greater magnification without greater resolution is of
little value.
Resolving power
It is a function of two factors as follows
a. Numerical aperture (NA)
b. Wavelength of the light (λ)
z
Numerical aperture: It is a numerical value related
with the diameter of the objective lens in association
to its focal length.
z
For calculating numerical aperture, the formula is as
following:
Numerical aperture = n sin θ
where,
n = Refractive index of the medium present between the
object and the objective lens.
θ = Half aperture angle
z
For air, the value of ‘n’ is 1.00
z
For specialized immersion oils, the value of ‘n’ is 1.51
z
If the wavelength (λ), of light is small then the ability
to resolution is high.
z
The limit of resolution of an objective (D) is the distance
between any two closest points on the object, which
can be resolved into two discrete and clear points on
the magnified image.
z
Smaller ‘d’ is obtained by increasing the resolving
Fig. 2.2: Phase contrast microscope
power, which in turn is obtained by using shorter
wavelength of light (λ) and greater numerical aperture.
z
For calculating limit of resolution, the formula is as
follows:
Limit of resolution = d = λ/2 na
where,
λ = Wavelength of light and
na = Numerical aperture of the objective
z
Magnification: The ability of the microscope to magnify
the object which is expressed as the ratio of the size of
the image to that of the object. The total magnification
obtained in a compound microscope is the product
of objective magnification and ocular magnification.
z
For calculating magnification, the formula is as
follows:
M
= Mob ×× M
t
oc
where,
M
= Total magnification
t
M
= Objective magnification
ob
M
= Ocular magnification
oc
z
The ratio of numerical aperture and magnification
power of microscope determines the image brightness.
Fluorescence Microscope
A biological microscope that observes fluorescence emitted
by samples by using special light sources such as mercury
lamps (Fig. 2.3).
Electron Microscope
Uses an accelerated electron beam as a source of
illumination.
Having a high resolution of images, able to magnify
objects of nanometres range
The electron gun generates electrons.
Uses electromagnetic and/or electrostatic lenses to
control the path of electrons and focuses it to form an
image.
The voltage of 100–1000 kV is applied between tungsten
filament and anode.
The electronic beam passes through the specimen and
electrons are scattered depending upon the thickness
or refractive index of different parts of the specimen
(Fig. 2.4).
Phase Contrast Microscope (Fig.2.2)
Principle
Phase-contrast microscopy is a form of microscopy
used to generate contrast to the image. In bright field
microscopy, the specimen is stained to generate contrast
with respect to the background.
Used for observing the different organelles and internal
structures of live cells.
In phase-contrast microscopy, the background is bright
and the specimen would be darker.
Fig. 2.3: Fluorescence microscope
Section 5 Microbiology
461460
Fig. 2.4: Electron microscope
MULTIPLE CHOICE QUESTIONS
1. The image obtained in a compound microscope
is:
A. Real B. Virtual
C. Real inverted D. Virtual inverted
2. Inuorescencemicroscopy,whichofthefollowing
performs the function of removing all light except
the blue light?
A. Exciter filter B. Barrier filter
C. Dichroic mirror D. Mercury arc lamp
3. Enzyme responsible for alcoholic fermentation is:
A. Ketolase B. Zymase
C. Peroxidase D. Oxidase
4. First Pasteur conducted fermentation experiments
in:
A. Milk B. Food material
C. Fruit juices D. Both A and C
5. Oilimmersion,objective lenshas an NAvalue
of____________
A. 0.65 B. 0.85
C. 1.33 D. 1.00
6. Vaccinationwasinventedby____________
Section 5 Microbiology
A. Jenner
B. Pasteur
C. Watson Crick
D. Both A and B
7. _________knownasfatherofmedicalmicrobiology.
A. Pasteur B. Jenner
C. Koch D. AV Leuwenhoek
8. Whichof thefollowingmethods isused for
viewingspirochetes?
A. Bright-field microscopy
B. Phase-contrast microscopy
C. Dark-field microscopy
D. Electron microscopy
9. The main feature of a prokaryotic organism is:
A. Absence of locomotion
B. Absence of nuclear envelope
C. Absence of nuclear material
D. Absence of protein synthesis
10. Inphasecontrast microscopy,the rate atwhich
lightentersthroughobjectsis_________constant.
A. Inversely proportional to their refractive indices
B. Directly proportional to their refractive indices
C. Exponentially related to their refractive indices
D. Both A and C
11. Tuberculosis is a:
A. Waterborne disease
B. Airborne disease
C. Food-borne disease
D. Arthropod-borne disease
12. Which part of the light microscope controls the
intensityoflightenteringtheviewingarea?
A. Coarse adjustment screw
B. Fine adjustment screw
C. Diaphragm
D. Condenser lens
13. The colonies of mycoplasmas in agar plate can be
observed by means of a __________________.
A. Low-power microscope
B. High-power microscope
C. Phase contrast microscopy
D. Bright-field microscopy
14. The transfer of genetic material during
transformation is proved based on Griffith’s
experiment by:
A. Avery Macleod and McCarthy
B. Lederberg and Taulum
C. Zinder and Lederberg
D. Watson and Crick
15. Themagnicationpowerofelectronmicroscope
developed by Knoll and Ruska is:
A. 10,000× B. 12,000××
C. 15,000× D. 20,000××
16. Hybridomatechniquewasrstdiscoveredby:
A. Kohler and Milstein
B. Robert Koch
C. ‘D’ Herelle
D. Land Steiner
17. What is the minimum distance for the eye to focus
onanyobject?
A. 11 cm B. 25 cm
C. 32 cm D. 42 cm
18. Monoclonal antibodies areassociated with the
name of:
A. Burnet B. Medwar
C. Milstein Kohler D. Owen
19. Which ofthe following isused inanelectron
microscope?
A. Electron beams
B. Magnetic fields
C. Light waves
D. Electron beams and magnetic fields
20. Compoundmicroscopewasdiscoveredby:
A. AV Leuwenhoek
B. Pasteur
C. Janssen and Hans
D. None of the above
21. Lederberg and Tatum (1946) described the
phenomena of:
A. Conjunction B. Transformation
C. Mutation D. Plasmids
22. 3% similarity (%S) of each strain to every other
strainiscalculatedbywhichmethod?
A. Intuitive method
B. Numerical taxonomy
C. Genetic relatedness
D. DNA homology experiments
23. Reductionofvirulenceisknownas:
A. Exaltation B. Attenuation
C. Both A and B D. None of these
24. The secondary electron radiated back in scanning
microscope is collected by:
A. Specimen B. Vacuum chamber
C. Cathode D. Anode
25. Salt and sugar are used for the preservation of
foods because they:
A. Convert them into acid
B. Make a hypotonic environment
C. Cause deficiency of nutrients
D. Produce a hypertonic environment
26. The causative organism of rocky mountain spotted
feverwasrstdescribedby:
A. Howard Ricketts
B. da Rocha-lima
C. Both A and B
D. Robert Koch
27. Electronmicroscopecangiveamagnicationup
to ___________
A. 400,000×× B. 100,000××
C. 15000× D. 100×
28. Condensation of light in light microscope is by:
A. Objective B. Condenser
C. Ocular D. All of these
29. Degree of scattering in transmission electron
microscope is a function of __________.
A. The wavelength of electron beam used
B. Number of atoms that lie in the electron path
C. Number and mass of atoms that lie in the
electron path
D. Mass of atoms that lie in the electron path
30. The most important virulence factors are:
A. Adhesions B. Invasiveness
C. Toxigenicity D. All of these
31. Whichamongthefollowingkingdomswas/were
proposed by Whittaker?
A. Monera
B. Protista, fungi
C. Plantae, animalia
D. Monera, protista, fungi, plantae, animalia
32. E. coliwasrstisolatedby:
A. Louis Pasteur B. Escherich
C. Shiga D. Robert Koch
33. Whichamongthefollowinghelpsusingettinga
three-dimensional picture of the specimen?
A. Transmission electron microscope
B. Scanning electron microscope
C. Compound microscope
D. Simple microscope
Section 5 Microbiology
463462
34. Mycobacterium tuberculosiswasrstdiscovered
by:
A. Robert Koch
B. Edward Jenner
C. Louis Pasteur
D. None of the above
35. Wheredoweobtainthemagniedimageofthe
specimen in SEM?
A. Cathode ray tube
B. Phosphorescent screen anode
C. Scanning generator
D. Both B and C
36. In an electron microscope source of electrons is:
A. Mercury lamp
B. Tungsten metal
C. Both A and B
D. None of the above
37. Fluorescent substance(s) used in fluorescent
microscopyis/are:
A. Quinine sulphate
B. Auramine
C. All of the above
D. None of the above
ANSWER KEY
1. B 2. A 3. B 4. C 5. C 6. A 7. C 8. C 9. B 10. A 11. B 12. C 13. A 14. A
15. B 16. A 17. B 18. A 19. B 20. C 21. A 22. B 23. B 24. D 25. D 26. C 27. A 28. B
29. C 30. D 31. D 32. B 33. B 34. A 35. A 36. B 37. C
3. Staining Methods
Stains or dyes, contain a positively charged ion and a negatively
charged ion. Depending on the type of dye, the positive or the
negative ion may be a coloured ion (chromophore) or on the
other hand, an uncoloured ion (known as counter ion).
If the coloured ion has a positive charge, the stain is
known as a basic dye
If the coloured ion has a negative charge, the stain is
known as an acidic dye
Basophilic objects are stained with basic dyes
Acidophilic objects are stained with acid dyes
Vital staining: The procedure to stain structures of living
cells either in vitro or in vivo.
Direct staining: Application of simple dye to stain the
tissue in varying shades of colours.
Indirect staining: It means use of mordant to facilitating
a particular staining method or the use of accentuator to
improve either the selectivity or the intensity of the stain.
Example of Basic Dyes
Basic fuchsin
Crystal violet
Malachite green
Methylene blue
Safranin.
Example of Acidic Dyes
Acid fuchsin
Eosin.
Gram Staining
Danish microbiologist Hans Christian Gram developed
gram staining in 1884. It is used for distinguishing
between various types of bacteria.
Section 5 Microbiology
This differential staining method distinguishes most
bacteria into two groups on the basis of their cell-wall
composition.
Cell-wall composition of bacteria determines whether
the bacteria is gram-positive or negative.
When bacteria are stained with a primary stain and
then fixed by a mordant, some bacteria can retain the
primary stain by resisting decolourisation while others
get decolourised after applying decolourizer.
Those bacteria which retain the primary stain are called
gram-positive.
Those bacteria which get decolourized and then get
counterstained are called gram-negative.
Based on gram staining, we can classify bacteria into
two categories
1. Gram-positive bacteria—stains purple, e.g. Salmonella
typhi, Salmonella typhimurum, Pseudomonas aeruginosa,
Proteus merabilis, Acinetobacter, E. coli.
2. Gram-negative bacteria -stains red/pink, e.g.
Staphylococcus aureus, Staphylococcus epidermis,
Streptococcus pyrogens, Streptococcus pneumoniae,
Streptococcus fecalis.
Classic gram staining technique
These involve the following steps (Fig. 3.1):
1. Fixation of bacteria by heating or by using methanol.
2. Application of the primary stain (crystal violet). Stains
all cells to blue/purple colour.
3. Application of mordant [iodine solution forms a crystal
violet-iodine (CV-I) complex].
4. Application of decolourizer helps distinguish gram-
positive from gram-negative cells.
5. The gram-negative bacteria appear colourless and gram-
positive bacteria remain blue.
6. Application of counterstain (safranin).
Fig. 3.1: Steps of Gram-staining technique
Special staining methods
Capsule staining: Helps the bacterial cell to attach to
surfaces and to avoid being phagocytosed.
Most bacteria and some yeasts have an outer structure
called a capsule also known as slime layer/glycocalyx,
an extracellular polymeric substance. It is viscous in
nature.
Capsular material is very moist in nature, it will shrink
on heating—this is the reason why we will not heat fix
the slide before staining in case of capsule staining.
Negative staining methods are the most preferred
techniques for staining of capsules because capsules do
not absorb most of the basic dye.
The dye stains the background but does not penetrate
the capsules, which appear like halos around the borders
of the cell.
Endospores staining: Spores are high resistant structures
that are difficult to destroy by heat or other physical and
chemical agents.
This staining technique uses two stains to distinguish
between endospores and the rest of the cell.
The Schaeffer-Fulton method uses heat to push the
primary stain (malachite green) into the endospore.
Washing with water decolourizes the cell, but the
endospore retains the green stain. The cell is then
counterstained pink with safranin.
The resulting image reveals the shape and location of
endospores, if they are present.
The green endospores will appear either within the pink
vegetative cells or as separate from the pink cells altogether.
If no endospores are present, then only the pink
vegetative cells will be visible.
Comparison of Various Types of Staining Technique
Method of staining Stain type Specic dyes Purpose Outcome
Simple staining Acidic stains Eosine, acid fuchsin,
rose bengal, Congo
red
Basic stains Methylene blue,
crystal violet, basic
fuchsin, carbolfuchsin,
safranin
Negative stains India ink, nigrosine Stains only
Stain positively
charged molecules
such as proteins
Stain negatively
charged molecules
such as nucleic acids
and proteins
background, not
Can either be a
positive or negative
stain
Can either be a
positive or negative
stain
Dark background with
a light specimen
specimen
Contd...
Section 5 Microbiology
465464
Method of staining Stain type Specic dyes Purpose Outcome
Differential staining Acid-fast stain Carbolfuchsin is used
as the primary stain
Aacid-fast bacteria
resist decolourization
by acid-alcohol. Nonacid-fast bacteria are
counterstained with
methylene blue.
Capsule stain Capsules do not
absorb most basic
dyes; negative
staining with India ink
or nigrosine is used to
stain the background
but is unable to
penetrate the capsule
Heat xing is not
required
Endospore stain Uses heat to stain
endospores with
malachite green,
wash the cell with
water. It decolourizes
the cell, but the
endospore retains
the green stain, next
counterstained with
safranin dye
Flagella stain Thicken the agella
rst by tannic acid
or potassium alum
mordant, then stained
using basic fuchsin
Gram stain Uses crystal violet,
Gram’s iodine, ethanol
and safranin
Used to distinguish
acid-fast bacteria
Used to differentiate
cells with capsules
and without capsules
Used to differentiate
organisms with
endospores from
those without
endospores
Used to study shape
and location of
endospore
Used to study agella
in bacteria
Used to differentiate
gram-negative and
gram-positive bacteria
Acid-fast bacteria—red
Non-acid-fast cells—
blue
Capsules appear clear
Endospores appear
bluish-green,
other structures
appear pink to red
Flagella are visible if
present
Gram-positive cells
stain purple/violet.
Gram-negative cells
stain pink
MULTIPLE CHOICE QUESTIONS
1. The bacterial cells are at their metabolic peak
during:
A. Lag phase
B. Log phase
C. Stationary phase
D. Decline phase
2. Ziehl-Neelsenstainingconsistsof:
A. 2 stages
B. 4 stages
C. 3 stages
D. 5 stages
3. Conjugationis:
Section 5 Microbiology
A. The transfer of genetic information through the
agency of free DNA
B. The transfer of a portion of the DNA from one
bacterium to another by a bacteriophage
C. The transfer of genes from a donor cell to a
recipient by means of physical contact
D. A random, undirected, heritable variation
caused by an alteration in the nucleotide
sequence at some point of the DNA of the cell
4. Whichofthefollowingistheexampleofgram-
negative bacteria?
A. Lactobacillus
B. Staphylococcus aureus
C. Bacillus subtilis
D. Escherichia coli
5. Gram-negative microorganisms stain:
A. Violet colour
B. Green colour
C. Pink-red colour
D. Black colour
6. Fixation of the smear is necessary:
A. To killed bacteria
B. For preventing bacteria from washing off
during staining
C. For best staining
D. All of the above
7. Protein particles that can infect are called:
A. Virons B. Prions
C. Nucleoida D. None of these
8. Bacteria that are responsible for the fermentation
of dairy milk are:
A. Azetobacter B. Rhizobium
C. Lactobacillus D. Hay bacillus
9. What is the correct order of staining reagents in
Gram staining?
A. Crystal violet, alcohol, iodine solution, safranin
B. Crystal violet, iodine solution, alcohol, safranin
C. Crystal violet, safranin, alcohol, iodine solution
D. Iodine solution, crystal violet, alcohol, safranin
10. Gram’s staining consists of:
A. 4 stages B. 2 stages
C. 3 stages D. 5 stages
11. F-plasmid (fertility factor):
A. Determines colicin production
B. Determines production of heat-labile and heat
stable endotoxins
C. Codes for a series of genes necessary for
conjugal transfer
D. Determines production of specific enzymes that
modify or destroy specific antibiotics
12. The centromere is that part of a chromosome
where:
A. Nucleoli are formed
B. Crossing over takes places
C. Chromatids are attached
D. All of the above
13. Transduction is:
A. The transfer of genetic information through the
agency of free DNA
B. The transfer of a portion of the DNA from one
bacterium to another by a bacteriophage
C. The transfer of genes from a donor cell to a
recipient by means of physical contact
D. A random, undirected, heritable variation
caused by an alteration in the nucleotide
sequence at some point of the DNA of the cell
14. Whichofthefollowingdoesnotuseforserotyping
of salmonellae?
A. Antigen B. H antigen
C. K antigen D. Vi antigen
15. During stainingfor electron microscopy,the
methodwhichimprovesthecontrastofspecimenis:
A. Positive staining
B. Negative staining
C. Shadow staining
D. None of the above
16. Cowscandigeststrawbecausetheycontain:
A. Cellulose hydrolysing microorganisms
B. Protein hydrolysing bacteria
C. Lipid hydrolysing microorganisms
D. Amino acid degrading bacteria
17. Whichof the followingis a simplestaining
method?
A. Gram B. Neisser
C. Zeihl-Neelsen D. Burri
18. Replicationistheprocessbywhich:
A. mRNA, in conjugation with tRNA and the
ribosome, directs the synthesis of specific
protein
B. Genetic information carried in the bacterial
DNA is transferred to mRNA
C. DNA is formed a new identical copy
D. Genetic information carried in the bacterial
RNA is transferred to DNA
19. Mycoplasmas are bacterial cells that:
A. Fail to reproduce on artificial media
B. Have a rigid cell wall
C. Are resistant to penicillin
D. Stain well with Gram’s stain
20. TranscriptionofbacterialDNAismediatedby:
A. DNA polymerase
B. RNA polymerase
C. DNA ligase
D. RNA ligase
21. The dye eosinate of methylene blue belongs to
whichgroup?
A. Acidic dye B. Basic dye
C. Neutral dye D. Oxazine dye
22. In thethird week,typhoid is diagnosedby all,
except:
A. Widal test B. Urine culture
C. Stood culture D. Blood culture
23. The order of stains in the Gram staining procedure is:
A. Crystal violet, iodine solution, alcohol,
saffranine
B. Iodine solution, crystal violet, saffranine,
alcohol
C. Alcohol, crystal violet, iodine solution,
saffranine
D. All of the above
24. Salmonella is a:
A. Gram-negative straight rod, motile by
peritrichous flagella. Capsules are found in
some strains. Spores are not formed
B. Gram-negative straight rod, usually motile by
peritrichous flagella. Does not form capsules or
spores
C. Gram-negative short rod, no motile, non-
sporing and non-capsulated.
D. Gram-negative curved bacteria, motile by
single polar flagellum, non-sporing and noncapsulated.
Section 5 Microbiology
467466
25. The parasitic form must contains:
A. Capsules B. Cell-wall
C. Endospores D. Flagella
26. Col-plasmids:
A. Determine colicin production
B. Determine production of heat-labile and heat
stable endotoxins
C. Determine production of haemolysins
D. Determine production of specific enzymes that
modify or destroy specific antibiotics
27. Gram-negative bacteria appear as:
A. Pink B. Violet
C. Both A and B D. None of these
28. Gram-positive bacteria are usually more
susceptible to:
A. Streptomycin B. Tetracycline
C. Penicillin D. Ampicillin
29. Translationistheprocessbywhich:
A. mRNA, in conjugation with tRNA and the
ribosome, directs the synthesis of a specific
protein
B. Genetic information carried in the bacterial
DNA is transferred to mRNA
C. DNA is formed a new identical copy
D. Genetic information carried in the bacterial
RNA is transferred to DNA–RNA ligase
30. Virulence of the microorganisms can be reduced
by:
A. Attenuation B. A virulence
C. Inactivation D. Freezing
31. Mutation factors:
A. Radiation B. Chemical agents
C. UV rays D. All of these
32. Cholera vaccine gives protection for:
A. 1–3 months B. 3–6 months
C. 6–9 months D. 9–12 months
33. Ent-plasmids:
A. Determine colicin production
B. Determine production of heat-labile and heat-
stable enterotoxins
C. Determine production of haemolysins
D. Determine production of specific enzymes that
modify or destroy specific antibiotics
34. Gram staining is an example for:
A. Simple staining
B. Differential staining
C. Negative staining
D. None of the above
35. Thecellwallofgram-negativebacteriais:
Section 5 Microbiology
A. Thick
B. Lipids are present
C. Teichoic acids are absent
D. None of the above
36. Widal reaction detects:
A. Antibodies
B. H- and O- antibodies
C. H antibodies
D. Vi antibodies
37. Nitriteisconvertedintonitratebythebacteria:
A. Nitrosomonas B. Nitrosocytes
C. Nitrobacter D. Azatobacter
38. Rod-shapedbacteriaareknownas:
A. Cocci B. Comma forms
C. Bacilli D. Plemorphic froms
39. A mutation may produce changes in:
A. Morphology
B. Susceptibility to antibiotics
C. Enzyme activity
D. All of the above
40. NegativeStainingisusedforexamining_______.
A. Virus particles
B. Protein molecules
C. Bacterial flagella
D. Virus particles, protein molecules and bacterial
flagella
41. ClassicationwithinthegenusSalmonella is on
antigenic characterization based on:
A. Voges-Proskauer scheme
B. Kauffmann-White scheme
C. Mac Conkey scheme
D. Kauffmann scheme
42. Shigella is a:
A. Gram-negative straight rod, motile by
peritrichous flagella. Capsules are found in
some strains. Spores are not formed
B. Gram-negative straight rod, usually motile by
peritrichous flagella. Does not form capsules or
spores
C. Gram-negative short rod, no motile, non
sporing and non-capsulated
D. Gram-negative curved bacteria, motile by
single polar flagellum, non sporing and noncapsulated
43. Thylakoid is present in:
A. Mitochondria B. ER
C. Golgi apparatus D. Chloroplast
44. Mutation is:
A. The transfer of genetic information through the
agency of free DNA
B. The transfer of a portion of the DNA from one
of bacterium to another by a bacteriophage
C. The transfer of genes from donor cell to recipient
by means of physical contact
D. A random, undirected, heritable variation
caused by an alteration in the nucleotide
sequence at some point of the DNA of the cell