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Fundamentals of Microbiology > Introduction and Review (Lecture 1) > Flashcards

Introduction and Review (Lecture 1) Flashcards

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1
Q

Definition of Microbiology

A

Microbiology is the study of microbes- that is living organisms that are too small to be observed by the naked eye. Microscopes are required for the study and observation of microbes.

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2
Q

How long has microbes been on earth for?

A

Almost 4 billion years

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3
Q

Who came up with the Primordial Soup theory?

A

It was independently proposed by Oparin and Haldane in 1920’s.

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4
Q

What are the three domains of living organisms?

A

Bacteria, Archaea and Eukarya

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5
Q

The cell theory was formulated by who?

A

Schleiden and Schwann

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6
Q

What is the cell theory?

A

The cell theory states that cells are the fundamental units of all living organisms.

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7
Q

Do prokaryotes have a nucleus and membrane-bound organelles?

A

No prokaryotes lack a nucleus and other membrane-bound organelles.

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8
Q

Do eukaryotes have a nucleus and membrane-bound organelles?

A

Eukaryotes have a true membrane-bound nucleus as well as a host of membrane-bound organelles.

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9
Q

What is the size of the cell of a prokaryote and eukaryote?

A

Prokaryote- typically about 0.2-2.0 nanometer in diameter

Eukaryote- typically about 10-100 nanometer in diameter

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10
Q

Compare the nucleus of prokaryotes and eukaryotes

A

Prokaryotes have no nuclear membrane or nucleoli whereas eukaryotes have a true nucleus consisting of nuclear membrane and nucleoli

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11
Q

Compare membrane-enclosed organelles in prokaryotes and eukaryotes.

A

Prokaryotes do not have any membrane-enclosed organelles whereas eukaryotes have such as lysosome,Golgi complex etc

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12
Q

Compare Glycocalyx of prokaryote and eukaryote

A

Glycocalyx is present as a capsule or slime layer in prokaryotes whereas it is present in
some cells that lack a cell wall in eukaryotes

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13
Q

compare cell walls of prokaryote and eukaryote.

A

the cell wall in prokaryotes is usually present and it is chemically complex. when the cell wall is present in eukaryotes, it is chemically simple

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14
Q

size of ribosomes in prokaryotes vs eukaryotes

A

Prokaryotes have a smaller sized ribosomes at 70S whereas eukaryotes ribosomes are larger sized at 80S or they can have smaller size of 70S in organelles

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15
Q

what is the shape of the chromosome DNA is eukaryotes and prokaryotes?

A

In prokaryotes the DNA chromosome is usually single circular and lacks histones whereas in eukaryotes there are multiple linear chromosomes present with histones.

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16
Q

How does cell division happen in prokaryotes and eukaryotes?

A

in prokaryotes, cell division happens by binary fission and in eukaryotes by mitosis.

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17
Q

how does sexual recombination occurs in prokaryotes and eukaryotes?

A

in prokaryotes there is no sexual recombination, just the transfer of DNA fragments only and in eukaryotes, meiosis is involved.

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18
Q

The prokaryotes comprise of which two domains?

A

Archaea and Bacteria

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19
Q

How are the two domains distinguished from each other?

A

Archaea and Bacteria differ primarily in their cell wall, membrane lipids, antibiotic sensitivity and first amino acid in protein synthesis

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20
Q

What are the three major groups of Archaea ?

A

Methanogens, extreme halophiles and Extreme theromoacidophiles.

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21
Q

What is extreme halophiles?

A

These are generally obligate aerobes and they thrive in highly saline environments such as the dead sea and the great salt lake.

22
Q

What is extreme thermoacidophiles?

A

They survive in optimum growth temperatures that usually exceed 80 degrees, they possess heat stable enzymes known as extremozymes and they usually colonize hot springs and hydrothermal vents.

23
Q

What are the three basic shapes that bacteria show?

A

spherical, Rod-like and spiral

24
Q

Describe the shape of coccus bacteria?

A

Spherical

25
Q

Describe the shape of bacillus bacteria?

A

Rod-shaped

26
Q

Describe the shape of spirillum bacteria?

A

Spiral-shapes

27
Q

Describe the shape of cocobacillus?

A

Short rods

28
Q

Describe the shape of vibrio bacteria?

A

Comma-shaped

29
Q

Describe the shape of Spirochete bacteria?

A

Corkscrew-shaped

30
Q

What is pleomorphism?

A

Bacteria that show major variations in morphology

31
Q

After cell- division bacteria adopt different cellular arrangements of diplococci, streptococci,tetrads , sarcinae, and staphylococci. Describe each.

A

Diplococci- bacteria remain in pairs after dividing
streptococci- bacteria remain attached in a chain-like pattern.
tetrads-bacteria divide in two planes and remain in groups of four.
sarcinae-bacteria divide in three planes and remain in groups of eight.
Staphylococci- bacteria divide in multiple planes and remain in clusters.

32
Q

What are stains?

A

stains are usually organism salts comprising negative and positive ions, one of which is coloured.

33
Q

What are basic and acidic dyes?

A

Basic dyes are dyes in which the positive ion is coloured whereas the acidic dyes are those which the negative ion is coloured.

34
Q

What are the three basic staining techniques?

A

Simple, gram and special staining

35
Q

What is simple staining?

A

These are either aqueous or alcohol solutions of a single basic dye.
The purpose of this stain is to visualize the entire microorganism making the cellular structure and morphology identifiable.

36
Q

Why is the chemical additive mordant applied?

A

i. it intensifies the stain
ii. it increases the affinity of the stain for the specimen
iii. Act as a coating.

37
Q

What are three examples of simple stains?

A

Crystal violet, methylene blue and safrinin

38
Q

What is differential staining?

A

These stains have the advantage of distinguishing between different types of bacterial cells since they react variably.

39
Q

What are the two most common differential stains used for bacterial preparations?

A

The gram stain and acid-fast stain.

40
Q

What is the gram stain used for?

A

The gram-staining technique is used to distinguish between two main groups of bacteria and is based on the nature of bacterial cell walls.

41
Q

Describe the difference between gram-positive and gram-negative bacteria.

A

Gram-positive bacteria have cell walls comprising of a thick layer of peptidoglycan and Gram-negative bacteria have cell walls comprising of a thin layer of peptidoglycan sandwiched between the plasma membrane and an outer membrane. the inter-membrane space is known as the periplasm.

42
Q

Describe the steps taken to carry out the gram-staining procedure.

A 
step 1- crystal violet
step 2-rinse for 2 seconds
step 3- add grams iodine for 1 minute
step 4- decolourize with alcohol 
step 5- wash
step 6- add safranin for 20 seconds
step 7- wash
step 8- blot dry
43
Q

What group of bacteria is the acid-fast stain used for?

A

Namely used to identify bacteria in the genus mycobacterium .

44
Q

What does the acid-fast stain do?

A

The acid-fast stain make use of the dye carbol-fuchsin which binds strongly to lipids in the cell wall of certain bacteria.

45
Q

How is the acid-fast stain carried out?

A

The fixed bacterial smear is washed with carbol-fuchsin and heated for several minutes to allow penetration into the cells. after cooling, acid alcohol is used to decolourize cells that are not acid-fast and therefore cannot retain the dye.

46
Q

Why do acid-fast cells retain the red dye?

A

The red dye is retained in acid-fast cells because carbol-fuchsin is more soluble in the waxy lipid components of the cell wall than in alcohol.
Counterstaining with methylene blue allows visualization of non-acid fast bacteria.

47
Q

What are special stains?

A

These stains are very specific and is used to identify certain features of microbial cells.
examples include endospore staining, flagella staining and capsule staining.

48
Q

What is negative staining?

A

This can be used to detect the presence of diffuse capsules surrounding bacteria. it requires the use of an acidic stain such as negrosin or india ink.

49
Q

How does negative staining work?

A

Since these stains are negatively charged, they cannot penetrate the cells. The surface of bacterial cells is negatively charged. the unstained cells will be easily discernible against the coloured background.

50
Q

What are the two advantages of negative staining?

A

there is no fixing required and it enables visualisation of bacteria that are difficult to stain.

51
Q

What is endospore staining?

A

The spore stain uses two different reagents. Typical staining procedures do not work due to the impervious nature of the spore coat.

52
Q

How is endospore staining done?

A

Malachite green is applied to the bacterial smear and heat is applied. Both the spore as well as the cell pick up the green stain. Tap water is then used as a decolourizing agent, however, the endospore retains the green stain since the stain does not have a strong affinity for the vegetative cell components.
Safranin is used as a counterstain.

Fundamentals of Microbiology (2 decks)

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