Microbio 3-18 structure function

Question 1

What are two important bacteriological procedures?

Answer 1

sterilization & aseptic technique

Question 2

What’s the difference between sterilization and aseptic technique?

Answer 2

Sterilization - preparation of media/instruments such that no living bacteria are present. Aseptic Technique: allows manipulation of sterilized material without bacteriological contamination

Question 3

What is the first basis of classification for bacteria? What are two examples? How are they classified today?

Answer 3

shape. 1) cocci (round-shaped) and 2) bacilli (rod-shaped). They are now classified depending on the extent of DNA sequence homology

Question 4

How do you identify a gram + from a gram - stain?

Answer 4

Gram + is violet; Gram - is red

Question 5

What are the 4 most important bacterial characteristics?

Answer 5

1) morphology of colonies on appropriate agar medium. 2) microscopic morphology and staining of individual bacteria. 3) biochemical profiles (ability to ferment a particular sugar). 4) specific antigens detected by known anti-sera

Question 6

What are Koch’s postulates? (4)

Answer 6

1) the MO must be PRESENT in all organisms suffering from the disease, but not in healthy organisms. 2) the MO must be isolated from a diseased organism and grown in pure culture. 3) the cultured MO should cause disease when introduced into a healthy organism. 4) the MO must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

Question 7

Can Koch’s postulates be applied to all MO? Why/Why not?

Answer 7

No, not all infectious bacterium will fulfill Koch’s postulates (ie those that cannot grow on laboratory medium, but requir a host cell to grow)

Question 8

What are Koch’s molecular postulates?

Answer 8

1) the phenotype under investigation should be ASSOCIATED significantly more often with a pathogenic organism than with a nonpathogenic member or strain 2) Specific INACTIVATION of a gene (or genes) associated with the suspected virulence trait should lead to a measurable derease in virulation 3) RESTORATION of full pathogenicity should accompany replacement of the mutated gene with the wild-type organism

Question 9

Name whether Fungi, Protozoa, and Bacteria have pathogens, are photosynthetic, or if they have a rigid cell wall.

Answer 9

Fungi has some pathogens, non-photosynthetic, and has a rigid cell wall. Protozoa have some pathogens, no rigid cell wall, non-photosynthetic. Bacteria have many pathogens, require organic compounds as energy source (but some of the are photosynthetic), and all (but one) have a rigid cell wall.

Question 10

MOs are divided into two sub-groups on the basis of the structure of the individual cell. What are they?

Answer 10

Prokaryotes and Eukaryotes

Question 11

What are examples of eukaryotes? (3) What are examples of prokaryotes? (1)

Answer 11

E: fungi, protozoa, algae. P: bacteria

Question 12

How do eukaryotes and prokaryotes differ in terms of their chromosomes and their segregation?

Answer 12

E: linear chromosomes contained within nuclear membrane (segregation involves mitosis) P: one circular chromosome not bound by a nuclear membrane (segregation does not involve mitosis)

Question 13

How do eukaryotes and prokaryotes differ in terms of their sexual reproduction?

Answer 13

E: sexual reproduction occurs by meiosis P: reproduction occurs by partial, unidirectional transfer of DNA

Question 14

How do eukaryotes and prokaryotes differ in terms of their membrane bound structures?

Answer 14

E: contains mitochondria that carries out oxidative phosphorylation. P: no mitochondria, but oxidative phosphorylation occurs at the cell membrane

Question 15

How do eukaryotes and prokaryotes differ in terms of their mobility?

Answer 15

E: motbility accomplished by cytoplasmic streaming (amoeboid movement) or by contraction of flagella (microtubule 9 doublet x 2 singlet arragement surrounded by cell membrane) P: flagella (flagellin subunits forming a central hollow tube) are present in some bacteria and it is not surrounded by cell membrane

Question 16

How do eukaryotes and prokaryotes differ in terms of their cell wall?

Answer 16

E: animal cells do NOT have cell walls. Higher plants/algae have cell walls that are comprised of CELLULOSE (glucose polymer). Fungi have cell walls that are comprised of CHITIN (acetyl glucosamine polymer) and B-1,3-GLUCAN. P: cell walls are comprised of PEPTIDOGLYCAN, which consists of N-ACETYL glucosamine (NAG) lined to MURAMIC ACID (acetyl glucosamine linked to lactic acid), D-AMINO ACIDS. and other UNUSUAL A.A.

Question 17

Penicillin affects with what component of the prokaryotic cell?

Answer 17

it inteferes with the formation of the peptidoglycan (ie it interferes with the cross-linking between polymer chains)

Question 18

What ribosomes are present in eukaryotes vs prokaryotes?

Answer 18

E: 80S, P: 70S (think: P’s are simpler and have a smaller ribosome)

Question 19

Sterols are present in eukaryotic cells, but absent in prokaryotic cells. What is the one exception?

Answer 19

mycoplasma, which may contain sterols in their membrane.

Question 20

In a clinical specmiens,how would you tell whether a cell is a bacteria or a cell from the host?

Answer 20

cells larger than 10µm are not bacteria

Question 21

How do eukaryotes and prokaryotes differ in terms of their RNA/protein synthesis?

Answer 21

E: RNA is transcribed in the nucleus, spliced, and transported out to the ER, where it is transported into protein. P: nascent RNA is translated as it is transcribed and RNA splicing does NOT occur

Question 22

Prokaryotes are subdivided into these two major groups:

Answer 22

bacteria (true bacteria) and archaea (which inhabit unusual environmental niches)

Question 23

What are the general morphological types of bacteria?

Answer 23

1) cocci (spherical), 2) bacillus (rod shaped), 3) curved rod or spiral

Question 24

How do most bacteria multiply?

Answer 24

binary fission

Question 25

What is binary fission?

Answer 25

form of asexual reproduction/cell division used by all prokaryotes, and some organelles within eukaryotic organisms (ie mitochondria). The single DNA molecule first replicates and each is then attached a different part of the cell membrane. A central tranvesere wall forms between the two daughter cells. When the cell begins to pull apart, the chromosomes are separated. Results in genetically identical cells

Question 26

What are filaments and what type of bacterial cells are they most common in?

Answer 26

filaments are bacteria cell-aggregates that occur when the daughter cells do not separate after completion of the transverse wall

Question 27

How are streptococci cells usually arranged?

Answer 27

chain of cocci

Question 28

How are staphylococci cells usually arranged?

Answer 28

irregular clusters

Question 29

How are aerobic bacilli cells usually arranged?

Answer 29

chains of rods (think hot dog links)

Question 30

how are corynebacterium cells (causes diphtheria) usually arranged?

Answer 30

stacks of rods or a variety of groupings arranged in chinese-characters like orientations

Question 31

What properties do the cell wall confer that a plasma membrane wouldn’t?

Answer 31

Because of the strength and rigidity of its wall, large changes in the osmotic pressure of the environment have little effect on cell shape. Mammalian cells lack a cell wall and therefore its shape will change depending on the ionic strength of the surrounding medium

Question 32

What are protoplasts?

Answer 32

a plant, bacterial or fungal cell that had its cell wall completely or partially removed using either mechanical or enzymatic means.

Question 33

T/F Protoplasts are affected by osmotic changes

Answer 33

True. Since they lack a cell wall, the cell can burst or shrink depending on the osmotic strength of the media

Question 34

What are the functions of the prokaryotic cell membrane? (3)

Answer 34

1) contains oxidative enzymes (cytochromes, quinones, ATPase) and resembles the inner membrane of the mitochondrial membrane. 2) contains enzymes that function in cell wall synthesis. 3) selective transport systems to deliver sugars, a.a., metals, etc and secreting toxins and certain enzymes.

Question 35

What is the periplasmic space? What’s in it? What type of bacteria is it found in? Where is it usually found?

Answer 35

located between the cytoplasmic membrane and outer cell wall; contains enzymes that degrade extracellular substances of high m.w. (ie amylase can degrade proteins or polysaccharides) and binding proteins. It is found in Gram - bacteria, between the inner and outer membranes

Question 36

What is the medical importance of the periplasmic space?

Answer 36

it may contain enzymes that degrade antibiotics (confers antibiotic resistance)

Question 37

Is periplasmic space found in gram + bacteria?

Answer 37

No

Question 38

Gram - bacteria has their degradative enzymes in their periplasmic space. Where do gram + bacteria keep theirs?

Answer 38

Since there is no periplasmic space in the gram + bacteria, they excrete degradative enzymes into the extracellular environment or tether them to their cell wall

Question 39

What is the nucleoid?

Answer 39

nuclear equivalent in the bacteria; contains all or most of the genetic material but is not surrounded by a nuclear membrane

Question 40

What are 2 things normally seen in EMs of bacterial cells?

Answer 40

ribosomes and cytoplasmic granules

Question 41

What are cytoplasmic granules? When are they usually formed? What function do they serve?

Answer 41

bodies of polymers (ie glycogen, phosphate) formed under conditions of excess nutrients; enables bacterial to store of large quantities of nutrients without increasing the osmolarity of the cytoplasm

Question 42

What is the significance of the cross-linking of polymer chains to form the peptidoglycan layer?

Answer 42

imparts strength and rigidity to the cell wall

Question 43

What is a naturally occuring anti-bacterial agent?

Answer 43

lysozyme (which is found in tears, bodily fluids) splits the glycosidic bonds between NAG and muramic acidd

Question 44

What are two major components of the cell wall?

Answer 44

peptidoglycan + different carbohydrate polymers (ie ribitol, teichoic acid (phosphate), or other sugars)

Question 45

What is ribitol?

Answer 45

sugar alcohol polymer that forms the outer layer of the bacterial cell wall. usually found in Gram +

Question 46

What is teichoic acid? What bacteria is it usually found in?

Answer 46

phosphate polymer that forms the outer layer of the bacterial cell wall; usually found in certain species (ie Staphylococcus (gram +))

Question 47

What is the antibody response of the host usually directed against?

Answer 47

carbohydrate polymers (ribitol or teichoic acid)

Question 48

What is the difference between gram + and gram + bacteria?

Answer 48

Gram + bacteria has a thick layer of peptidoglycan with a layer of different carbohydrate polymers and NO outer membrane. Gram - bacteria has a thin layer of peptidoglycan & outer membrane that contains LPS and an intervening periplasmic space

Question 49

Which bacterium has a periplasmic space? Gram + or gram -?

Answer 49

Gram -

Question 50

What are the components of a gram + bacteria?

Answer 50

Gram + bacteria has a thick layer of peptidoglycan intertwined with a layer of different carbohydrate polymers (ie teichoic acid) and NO outer membrane.

Question 51

What are the components of a gram - bacteria?

Answer 51

Gram - bacteria has a thin layer of peptidoglycan & outer membrane that contains LPS and an intervening periplasmic space (forming a 3 layered envelope)

Question 52

What are porins? What type of bacteria are they usually found in? Why is this medically important?

Answer 52

transport protein found in the outer layer of gram - bacteria; allows entry of nutrients and small hydrophilic molecules by passive diffusion. It is of medical importance because antibiotics can gain entrance into the periplasmic space through porins

Question 53

What roles do the outer membrane of the gram - bacteria serve? (3)

Answer 53

1) blocks entry of large molecules into periplasmic space since it does not contain the transport system of inner cytoplasmic membrane 2) reacts with antibodies 3) barrier to antimicrobial agents/detergents

Question 54

What generally makes gram - bacteria more resistant to antibiotics, antimicrobial agents, and detergents than gram + bacteria? Why?

Answer 54

outer membrane; it doesn’t contain transport systems that can allow these things to enter the cell

Question 55

What is vancomycin? What type of bacteria is it most effective against and why?

Answer 55

antibiotic that targets the cell wall. Effective against gram + but NOT gram - because it can’t cross the outer membrane (it’s too large to fit through the porins)

Question 56

What is LPS composed of? Which component confers antigenic specificity and which confers the toxicity?

Answer 56

polysaccharide (antigen specificity) and lipid A (toxicity)

Question 57

Where is lipid A found?

Answer 57

it is embedded within the lipid bilayer of the outer membrane

Question 58

What is the basis of immunological specificity of the polysaccharide in LPS?

Answer 58

The polysaccharide is composed of an outer layer of repeating oligosaccharide units called “O” antigens . The O antigens (sugars) impart immunological specificity to the cell since they predominate at the cell surface.

Question 59

What are O antigens?

Answer 59

Oligosaccharide units that form the outer layer of LPS; impart immunological specificity to the cell since they predominate at the cell surface.

Question 60

Where is the periplasmic space located? What type of bacteria would you find this in?

Answer 60

Gram - bacteria. Located between the cytoplasmic membrane + outer membrane

Question 61

T/F Gram + are characteristically more resistant to penicillin and detergents

Answer 61

False. It’s gram - bacteria that are generally more resistant to these because of the presence of the outer membrane, since it doesn’t contain transport systems that can allow these things to enter the cell

Question 62

What is endotoxin? What is an example of endotoxin? What is it responsible for? What type of bacteria is it normally found in?

Answer 62

It is a toxin that is kept “within” the bacterial cell and to be released only after destruction of the bacterial cell wall. Example: LPS - responsible for shock and fever during infections. It is normally found in Gram - bacteria

Question 63

In the gram stain, what step is the differential step to differentiate between gram + and gram - bacteria?

Answer 63

Ethanol treatment step. Only gram - bacteria will decolorize while gram + retain the dye-iodine complex and remain blue

Question 64

In the gram stain, what will happen if you leave the specimens in the ethanol step for too long?

Answer 64

both gram + and gram - cells will decolorize

Question 65

Why is it that gram + bacteria will remain blue while gram - bacteria will decolorize in the gram stain?

Answer 65

gram + have cell walls (thick mucopeptide layer + outer lipid membrane) that are largely impermeable to low m.w. compounds when the organisms are in 70% alcohol, which traps the dye-iodine complex in the cytoplasm. In gram - bacteria, the dye-iodine complex leaks out through the walls (since they contain only a thin layer of mucopeptide layer + outer lipid membrane)

Question 66

What are some of the reasons why a loss in “gram positiveness” occur?

Answer 66

1) if the culture is old (>30 hours) or 2) loss of cell wall integrity through autolytic activity (destruction of a cell through the action of its own enzymes)

Question 67

What is the capsule?

Answer 67

a layer that lies outside the cell wall of bacteria; usually polysaccharide in composition and confers pathogenicity (mutant bacteria that have lost the ability to produce capsule are able to grow in culture but have lost all pathogenicity)

Question 68

How does the capsule confer pathogenicity?

Answer 68

The capsule is considered a virulence factor because it enhances the ability of bacteria to cause disease (ie prevents phagocytosis). The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages

Question 69

T/F flagella are present on every bacteria

Answer 69

False. It is only present on motile bacteria, and not all bacteria are motile. In fact, motile bacteria may become non-motile in later stages of growth or in energy-poor conditions

Question 70

What’s the difference between peritrichous flagella and polar flagella?

Answer 70

Peritrichous flagella is when there are many flagella present over the whole surface of a cell. Polar flagella originates from one end of the cell only

Question 71

T/F flagella are easily identifiable through the resolving power of a light microscope

Answer 71

False. It can only be seen in an EM or with a special stain that deposits molecules to increase the diameter

Question 72

How are pili (fimbriae) different than flagella?

Answer 72

they’re filamentous surface appendages that are shorter than flagella

Question 73

T/F all bacteria of medical importance of pili

Answer 73

False. Most, but not all, bacteria of medical importance have pili

Question 74

What is the function of pili (fimbriae)?

Answer 74

provides a means of adherence to other cells, either bacterial or animal. Examples: Gonococci produce pili (fimbriae) that bind to specific receptors of cervical epithelial cells, and is an important virulence factor for gonorrhoea

Question 75

What is the F pili?

Answer 75

found on “male” donor strains of bacteria and is necessary for bacterial conjugation (allows for the transfer of DNA from one cell to another).

Question 76

What is the type IV pili?

Answer 76

responsible for the pili-mediated movement, where it extends and retracts and allows for the pushing and pulling of the bacteria across a surface

Question 77

What is the twitching motility? What is responsible for it?

Answer 77

Type IV pili. Responsible for the pili-mediated movement, where it extends and retracts and allows for the pushing and pulling of the bacteria across a surface

Question 78

What are some surface components that allow bacteria to adhere to specific target tissues?

Answer 78

1) specific receptors on host cell surface, 2) glycocalyx or slime layer on host cell surfaces 3) adhesins on the outer membrane of gram - or cell wall of gram + bacteria

Question 79

What bacteriums can form spores?

Answer 79

bacillus and clostridia

Question 80

When do spores form? Is this process reversible?

Answer 80

it’s a response to nutrient deprivation. Usually occurs after the log phase of growth. Under favourable conditions the spore can germinate (become an actively dividing bacterium)

Question 81

What are endospores?

Answer 81

a dormant, tough, and non-reproductive structure produced by certain bacteria; formation is usually triggered by a lack of nutrients, and usually occurs in gram + bacteria.

Question 82

What do spores look like when treated with a gram stain?

Answer 82

it will remain colorless because it is resistant to staining

Question 83

What does a vegetative cell mean?

Answer 83

used to describe the reproductive, or non-spore form of a bacteria

Question 84

What are some properties of a spore?

Answer 84

1) they’re dormant. 2) resistant to drying, chemicals, and heat (can survive boiling, but not 121˚C)

Question 85

What happens to the properties of a spore when it germinates?

Answer 85

germination is accompanied by a loss of heat resistance, swelling, and uptake of water.

Question 86

T/F all clostridia and bacillus form spores

Answer 86

True.

Question 87

T/F clostridia spores are stable for years

Answer 87

True. Clostridia tetanus spores can survive for long periods in soil and germinate when deposited in deep wounds, causing tetanus

Question 88

T/F Spores are rarely seen in old cultures.

Answer 88

Depends on the bacterial strain - clostridia TETANUS readily forms spores in older cultures but clostridia GANGRENE rarely forms spores. But a general rule of thumb is that spores are rarely seen in very young cultures.

Question 89

What is bacillus anthracis?

Answer 89

bioterror agent

Question 90

T/F Bacillus anthracis are stable for years

Answer 90

True.

Question 91

What triggers bacillus anthracis to germinate?

Answer 91

warm, wet nutrient-rich environment (ie lungs, which results in inhalation anthrax)

Question 92

What agents in growth medium serve as attractants? (positive chemoattractant)

Answer 92

sugars and amino acids

Question 93

What agents in growth medium serve as repellents (negative chemoattractant)

Answer 93

phenols and acids

Question 94

What are “tasters” in the microbiology world?

Answer 94

sensory chemoreceptors on the membrane that control the direction of flagellar rotation

Question 95

What type of movement does CCW rotation of the flagella generate?

Answer 95

straight line movement

Question 96

What type of movement does CW rotation of the flagella generate?

Answer 96

tumbling in place

Question 97

When bacteria are in the presence of an attractant, how do their flagellas move?

Answer 97

the CCW rotation of the flagella dominates, resulting in a straight-line movement towards the attractant

Question 98

When bacteria are in the presence of an repellent, how do their flagellas move?

Answer 98

CW rotation of the flagella occurs until the net movement is properly redirected away from the repellent