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PH1123 Microbiology > Bacteria > Flashcards

Bacteria Flashcards

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1
Q

what types of culture media are there?

A

liquid
solid

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2
Q

what does selective media do? aka enrichment media

A

suppress growth of a particular organism and enhance the growth of another

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3
Q

what is the difference between synthetic media and complex media?

A

synthetic media is chemically altered whereas complex media is an aquaeous solution of an animal or plant that already contain b vitamins carbs and hydrolysed proteins

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4
Q

why is trypsin favored over acids in hydrolysis?

A

because acids destroy amino acids more than trypsin

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5
Q

how are microorganisms differentiated in culture?

A

different fermentation patterns of different microorganisms help in identification

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6
Q

what are exacting microorganisms?

A

organisms that need blood, mill, or serum to grow

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7
Q

what are media requirements and their sources

A

protein → meat extract/milk/soya

proteolytic enzyme → trypsin

b vitamin → yeast extract

nutrients → glucose/carbs/satrch

asmotic pressure → NaCl

buffer → bicarbonate

agar → carb extract from seaweed

imparting low pH → lactic acid

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8
Q

define binary fission

A

process by which cell enlarges and elongates forming a cross wall that separates the cell into two or more cells equal compartments containing a copy of the genetic material, septum then forms to reduce connection until daughter cells separate

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9
Q

what is the bacterial cell composed of

A
  • cell wall
  • cytoplasm
  • nucleus
  • ribosomes
  • inclusion granukes
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10
Q

what is the function of the cell wall in a bacterial cell

A
  • maintenance of shape and integrity of bacterial cell
  • withstand osmotic pressure caused by high concentrations of ions in the cell
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11
Q

the cell walls of bacteria is composed of peptidoglycan, what is peptidoglycan?

A

chains crosslinked by short peptide bridges composed of alternating residues of n-acetyl muramic acid and n-acetyl glucosamine

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12
Q

the N-acetly muramic acid (NAM) in the peptidoglycan is attached to a tetrapeptide, what is this tetrapeptide made up of?

A
  1. L-alanine
  2. D-alanine
  3. D-glutamic acid

these are crosslinked via (direct peptide linkage) & (peptide interbridges)

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13
Q

what is the antimicrobial target of bacteria?

A

the presence of DAP and 2 amino acids in the D-configuration

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14
Q

what’s the difference between gram positive and gram negative bacteria

A
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15
Q

in gram positive bacteria, what is techoic acid made up of

A

ribitol phosphate and glycerol phosphate connected by phosphodiester bridges hence the negative charge of the gram-positive bacteria

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16
Q

why does gram negative bacteria have a positively charged cell wall?

A

The lipopolysaccharides impart a strongly negative charge to surface of Gram-negative bacterial cells.

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17
Q

describe the regions of the lipopolysaccharides of the gram-negative bacteria

A

Lipid A: glucosamine phosphate + fatty acid in the outer leaflet of the membrane, responsible for toxic and pyrogenicity.

Core: connected to Lipid A by ketodeoxytonate (KDO)

O-specific polysaccharide: 6 carbon sugars and deoxysugar (abequose)

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18
Q

what is the function of the outer layer of gram negative bacterial cell wall?

A
  • prevents enzymes in outer side the cytoplasm from diffusing away
  • resists dissolution by detergents
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19
Q

what is the periplasm?

A

region between the outer surface of cytoplasmic membrane and inner surface of outer membrane

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20
Q

what is the function of the plasmic membrane in bacteria?

A
  • energy generation
  • nutrient transport
  • electron transport
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21
Q

describe the structure of bacterial DNA

A

circular double stranded DNA

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22
Q

what is the unique antibiotic target in gram negative and positive bacteria?

A

negative: DNA gyrase
positive: topoisomerase IV

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23
Q

what are plasmids?

A

circular double stranded extrachromosomal DNA

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24
Q

what is the function of plasmids?

A
  • autonomous replication
  • antibiotic resistance
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25
Q

describe bacterial ribosomes

A

70s: dividedd into two subunits (50s & 20s)

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26
Q

what do inclusion granules of bacteria do?

A

repository of C/N/S/phosphorus for when nutrient depletion occurs

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27
Q

how are eukaryotic ribosomes different from bacterial ribosomes?

A

eukaryotic ribosomes are 80s divided into (40s-60s)

whereas bacterial ribosomes are 70s divided into (50s-30s)

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28
Q

what are the cell surface components of a bacterial cell?

A

flagella

fimbrae

pili

extracellular polysaccharides

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29
Q

what is the role of flagella in bacteria?

A

it provides motility, and flagellin protein allow flagellar motor movement

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30
Q

what is the function of fimbrae in bacteria

A

serve as adhesins that allow attachment to surfaces and initiate biofilm formation

it allows hemagglutination and cell clumping

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31
Q

what is the function of pili

A

allows the process of genetic exchange (conjugation)

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32
Q

what is therole of the S layer in bacteria

A

it serves as a permeabiliy barrier that increases the robust of cell

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33
Q

what is the composition of extracellular polysaccharides in bacteria

A

0.2% carbohydrates and 98% water

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34
Q

what types of extracellular polysaccharides are there in bacteria?

A

capsules: tight and rigid
slime: loose

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35
Q

what do slime and capsules do?

A
  • provide barrier against antibodies
  • protection against dissection
  • protection against phagocytes
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36
Q

what are the extracellular polysaccharides of:

(1) pseudomonas aeruginosa
(2) leuconostoc mesenteroides

A
  1. alginate
  2. dextran
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37
Q

define biofilm

A

bacteria attached to surfaces forming multilayered communities

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38
Q

how do bacteria adhere to surfaces

A

via fimbrae and extracellular polysaccharides

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39
Q

how do biofilms form

A

cells grow and divide, produce microcolonies and coalesce

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40
Q

how are biofilms protected from antibiotics?

A

enveloping of attached cell in extracellular polysaccharide matrix which allows bacteria to stick together on the surface

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41
Q

how do biofilms get their nutrients if they are strung together?

A

EPS hold bacteria at distance to form pores that allow the passage of nutrients

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42
Q

true or false

biolfilms are impossible to eliminate from surfaces

A

true

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43
Q

define sporulation

A

profound biochemical change to give rise to a specialized structure (endospore)

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44
Q

which bacterial genera is capable of sporulation?

A

bacillus

clostridium

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45
Q

how are spores eliminated?

A

ethelyne oxide + heat

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46
Q

how is the vegetative cell different from the spore?

A

Spores are inactive and dormant structures. Vegetative cells are actively growing cells that form the endospore. They can tolerate stress like chemicals, heat and radiation. They cannot manage in stressful environments.

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47
Q

what layers surround the core of the spore?

A

outermost layer: proteins + spore coats

cortex: loosely crosslinked peptidoglycan

central core which holds the genome

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48
Q

what does the dipicolinic acid + calcium ions complex of the spore do?

A

plays a role in heat resistance, whereby it leaves the core dehydrated by retaining only 10-30% of water

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49
Q

what do the core specific proteins of the spore do?

A

bind to DNA to prevent damage to the cell

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50
Q

true or false

pH of the spore is 1 unit lower than that of the vegetative cell

A

true

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51
Q

how is sporulation started?

A

Ceasing protein synthesis and activation of spore genes

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52
Q

what are the spore genes responsible for the activation of sporulation

A

SPO

SSP

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53
Q

What do SPO & SSP do?

A

they produce proteins that catalyze the production of dry, metabolically inert, resistant spores. which takes hours to complete

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54
Q

how do spores go back to their vegetative form?

A

by removing the stress that caused the sporulation

Germination

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55
Q

what happens when the spore goes back to its vegetative form?

A
  • loss of resistance
  • loss of calcium diplionate cortex components
  • degradation of core proteins
  • water uptake
  • new RNA + DNA
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56
Q

what is an opportunistic pathogen?

A

an organism that normally doesn’t cause harm but can cause disease when host’s resistance is low

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57
Q

what is an example of an opportunistic bacteria?

A
  • staphylococcus epidermidis, it is present normally on the skin but can be fatal on the heart valve
  • pseudomonas aeruginosa, lethal in immunocompromised
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58
Q

define bacterial toxins

A

bacteria products that cause host cell damage

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59
Q

what types of toxins are there

A

endotoxin: related to cell wall (Lipid A of LPS)

exotoxin (released extracellularly)

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60
Q

what types of exotoxins are there

A
  1. A-B toxins: most common, b subunit covalently bound to a subunit bound to host, mediate enzymatic activity responsible for toxicity (diptheria/cholera)
  2. cytolytic toxins: attack cell constituents causing lysis (phospholipases/haemolysins)
  3. superantigen toxins: stimulate immune response, releasing cytokines leading to massive inflammatory response (staphyloccocus aures) aka toxic shock
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61
Q

what type of toxins activate b lymphocytes, stimulate the complement cascade and the production of tumor necrosis factor

A

endotoxins

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62
Q

true or false

endotoxins are released from damaged cells

A

true

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63
Q

how long does E.coli take to multiply/divide?

A

45 minutes

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64
Q

how do gram positive and gram negative bacteria divide?

A

gram positive: develop a cross wall that divides into two due to the rigid cell wall

gram negative: constrict and fuse membrane, due to fragile cell wall

this process takes 15 minutes to complete

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65
Q

how is it possible for bacteria to grow/replicate every 15 minutes under optimal conditions

A

they replicate more than onxe every hour by initiating new rounds of DNA replication, therefore partially replicated chromosomes are separated into daughter cells thus making division quicker

66
Q

how do rods/cocci/streptococci/staphyloccoci/sarcina increase their size?

A

rods → elongation

cocci → radial expansion

streptococci → parallel planes (successive division)

staphylococci → successive division

sarcina → rotate successive division

67
Q

how do bacteria grow on solid surfaces?

A

creating a localized colony from moist and nutrients

68
Q

how do bacteria grow on liquids?

A

by nutrients diffusing through the colony

69
Q

what is solidified media?

A

broth that is solidified by agar below 45 celcius

70
Q

what are the methods by which bacteria exchange genetic material?

A
  1. transformation
  2. transduction
  3. conjugation
71
Q

what is transformation?

A

a process by which bacteria exchanges genetic material by absorbing small pieces of naked DNA from the environment and recombine it into their chromosomes

can lead to septic abscess

72
Q

what is transduction?

A

a process by which bacteria exchanges genetic material by bacteriophages infecting bacteria by injecting viral DNA into their cell and incorporate into bacterial chromosomes creating a temperate phage

73
Q

what is conjugation?

A

a process by which bacteria exchanges genetic material by generating defective viral DNA which is transcribed to produce viral elements that cannot assemble or lyse the host cell

74
Q

true or false

conjugation evolved from transduction

A

true

75
Q

what is the F-factor

A

simplest form of plasmid that generates f pilus in cell envelope (transfers DNA from one cell to another)

76
Q

what does the f-factor do in conjugation

A

transfers a copy of DNA from one cell to another

77
Q

what is the name of the integrated form of f factor

A

Hfr

78
Q

what does bacterial growth depend on

A
  • nutrients
  • water
  • partial pressure of oxygen
  • temperature
  • solute concentration
79
Q

what is the optimal environment for the growth of gram negative and grame positive respectively

A

negative: aquatic environments
positive: arid environments (skin)

80
Q

majority of bacteria are mesophiles, define mesophiles

A

grow at body temperature 37

81
Q

how are bacteria able to grow in high temperatures?

A

high temperatures speed up the chemical reactions within the bacterial cell thus enzymaticc and growth action occur rapidly

82
Q

most pathogens of medical significance grow at a pH of _____

A

(7.4-7.6)

83
Q

why do gram negative bacteria favor aquatic environments for growth

A

because their cell envelope cannot withstand high internal osmotic pressures associated with rapid dehydration of dessication and they would be unable to grow in high concentrations of solutes

84
Q

what is water activity Aw

A

vapour pressure of water in the space above the material relative to the vapour pressure above pore water at the same temp and pressure

85
Q

what elements are the terminal electron acceptors in respiration

A

iron

oxygen

lactic acid

sulfur

86
Q

what are obligate anaerobes

A

organisms toxicated by oxygen

87
Q

what type of culture is used to grow anaerobes?

A

special media and anaerobic chambers

88
Q

why are bacteroides and fusobacter found in the GI tract along with streptococci?

A

because the close proximity of strongly anaerobic and aerobic cells will create an anoxic microenvironment in whch the anaerobe can flourish

89
Q

what causes stationary phase in bacterial growth?

A

the inability of oxygen to diffuse adequately into a liquid culture

90
Q

fill in the blanks

A
91
Q

what is the gram stain

A

a staining technique for the preliminary identification of bacteria, in which a violet dye is applied, followed by a decolorizing agent and then a red dye. The cell walls of certain bacteria (denoted Gram-positive ) retain the first dye and appear violet, while those that lose it (denoted Gram-negative ) appear red.

92
Q

what are the properties of the bacterial cytoplasmic membrane?

A
  • 40% lipid (much in the form of phospholipids)
  • 60% protein and small amounts of carbohydrates
  • no sterols
  • Semi-permeable. Generally, only low molecular weight materials can penetrate to the inside of the cell.
  • has efflux proteins (vomit pumps)
  • Contains many proteins/enzymes essential to the bacterium survival; e.g. the proton motive force that generates adenosine triphosphate (ATP; energy
93
Q

Many bacteria form and store granules in their cytoplasm in the form of high molecular weight polymers. these are:

A
  • glycogen: a storage form of both carbon and energy
  • polymer of β-hydroxybutyric acid (storage form of both carbon and energy)
94
Q

Protein crystals are sometimes found. Bacillus thuringiensis crystals are used as ____

A

insecticide

95
Q

define bacterial growth

A

Change in the population rather than an increase in the size or mass of the individual bacterium

96
Q

describe what happens in each phase of bacterial growth

A

Lag Phase

  • Population remains temporarily unchanged.
  • Bacterial cells may be growing in volume or mass, synthesizing enzymes, proteins, RNA, etc., and increasing in metabolic activity.

Exponential growth phase

  • Expressed as generation time, or doubling time of the bacterial population.

Stationary Phase

population growth is limited

  • Exhaustion of available nutrients
  • Accumulation of inhibitory metabolites or end products
  • Exhaustion of space
97
Q

what happens in exponential growth phases?

A

One cell divides producing 2 (‘daughter’) cells. Increase in population is by geometric progression

Total population b at the end of a given period (starting with 1 cell) b = 1 x 2n

98
Q

what is a chemostat?

A

Chemostat: bioreactor to which fresh medium is continuously added, while culture liquid is continuously removed to keep the culture volume constant

99
Q

what is the optimal temperature for the growth of each of the following:

psychrophiles / mesophiles/ thermophiles

A
  • Psychrophiles: 0-20ºC (optimum temperature: 15ºC)
  • Mesophiles: 25-40ºC
  • Thermophiles: >45ºC
100
Q

Control of temperature is essential for the storage of pharmaceutical products. how is that acheived?

A
  • deep freeze (-20ºC) Total Parenteral Nutrition, raw materials - 8-12ºC: reconstituted syrups and multi-dose eye drops (expiry date) - 80ºC for WFI (regrowth of Gram-negative and release of toxins)
101
Q

explain how pH controls growth of bacteria

A
  • extreme pH prevent microbial growth
  • neutral pH: bacterial spoilage e.g. in antacid mixtures, flavoured mouth washes, distilled and deionised water -
  • pH>8: spoilage is rare (soap-based emulsion)
  • low pH: spoilage by moulds and yeast e.g. fruit juice flavoured syrups
102
Q

true or false

The greater the solute concentration, the lower the water activity

A

true

103
Q

Water activity of aqueous formulations can be lowered to decrease microbial growth, how can that be achieved in syrup?

A

Syrup BP: (Aw = 0.86)

104
Q

list the nonsterile pharmaceutical products

A

• Preparations for topical use and for use in the respiratory trac

t • Preparations for oral and rectal administration

  • Preparations for oral administration containing raw materials of natural origin
  • Herbal remedies
105
Q

define sterile pharmaceutical products

A

Preparations required to be sterile on the dosage form and other preparations labelled sterile, need to comply with test for sterility.

106
Q

what are the acceptable counts for each pharmaceutical product

A
107
Q

define colony count

A

The viable count referred as to the number of colony-forming units (cfu)

108
Q

what Plate count methods are there

A
  1. pour plate
  2. spread plate
109
Q

true or false

The Most Probable Number method is reserved for the enumeration of bacteria in situations where no other method is available.

A

true

110
Q

what rapid microbiology methods (RMM) are there?

A
  • growth based (OD)
  • direct measurement (DEFT)
  • cell component (NAAT)
111
Q

what is phylogeny?

A

study of the evolution of organisms

112
Q

why are the domains of life classified on the basis of rRNA?

A

because rRNA are present in all living cells

113
Q

provide examples of biochemical profiling methods

A
  • Example Fermentation of various sugars (acidity turn colour yellow)
  • Production of oxidase (presence of cytochrome oxidase)
  • Hydrogen sulphide production (production of H2S, will react with iron salts forming a black precipitate)
114
Q

what does Serological testing use?

A

highly specific antibody (Ab) antigen (Ag) interaction

115
Q

what is an example of a serological test?

A

Enzyme Linked Immunosorbent Assay (ELISA)

116
Q

how does PCR work

A

Polymerase Chain Reaction (PCR) based techniques allow amplification of a known gene of interest for nucleic acid sequencing, which provide accurate identification of the genus

117
Q

draw an endospore cell

A
118
Q

what’s the difference between sporulation and germination?

A

Germination is the process by which a spore reverts into a (vegetative) bacterium.

sporulation is when the vegetative cell turns into a spore

119
Q

true or false

Spores are used as biological indicators for sterility assurance of sterilization process.

A

true

120
Q

The use of broad spectrum chemotherapeutic antibiotics is associated with an increased risk of developing ________

A

C. difficile associated disease (CDAD).

121
Q

list 3 of each

5 broad spectrum antibiotics

5 low risk antibiotics

A
122
Q

Chlamydia are obligate intracellular bacteria, what does that mean?

A

they lack the metabolic pathway to produce their own high-energy phosphate compounds (“energy parasites”)

123
Q

chlamidya exist in two forms. what are they?

A
  • the small (300-400nm) extracellular infectious elementary body (EB)
  • the larger (800-1000nm) intracellular non-infectious reticulate body (RB)
124
Q

describe the structure of chlamidya

A

Microbial structure

  • internal and external membrane similar to Gram-negative bacteria
  • no peptidoglycan layer
  • lipopolysaccharide
  • no flagella and non piliated
125
Q

how is chlamydia treated?

A

Tetracyclines: doxycycline 100 mg bds; 7 days

  • Macrolides: azithromycin 1g : single dose.
126
Q

how do you prevent chlamydia?

A
  • safe sex
  • not sharing sex toys
  • appropriate sanitary hygiene
127
Q

draw the structure of mycobacterium tuberculosis

A
128
Q

name one a characteristic of virulent strains of M. tuberculosis

A

cord formation

129
Q

list risk patients of tuberculosis

A

1) close contacts of an infectious case
2) those who have lived in places where TB is still common
3) those whose immune system is weakened by HIV or other medical conditions
4) people who experience chronic poor health through lifestyle factors such as homelessness, alcoholism and drug abuse
5) young children and very elderly people are more susceptible

130
Q

describe the structure of the cell wall of mycobacterium tuberculosis

A

Basic layer: peptidoglycan linked to an arabinogalactan wall (copolymer of arabinose and galactose) esterified to mycolic acid structure.

131
Q

what is mycolic acid

A

High-molecular-weight (60-90 carbons) 3-hydroxy fatty acid found in mycobacteria

132
Q

25% of the dry weight is free lipids located outside the outer layers.

what lipids exist in a mycobacterium cell?

A
  • Lipids include waxes,
  • species-specific mycosides (complex glycolipids and peptidoglycolipids),
  • lipopolysaccharides
  • cord factor (6,6”-dimycolate of trehalose)
133
Q

Anti-TB drugs are always prescribed in combination, why?

A

to reduce the risk of the TB bacilli becoming resistant to one or more of them

134
Q

It is vital that the medication is taken as prescribed. why?

A

taking anti-TB medication in the wrong dose, intermittently or for too short a time can result in the development of drug resistance

135
Q

what are the first line of treatment in tb

A

isoniazid, rifampicin, pyrazinamide, ethambutol

136
Q

how do you treat a newly diagnosed tb patient? and how do you re-treat a patient?

A

newly diagnosed

  1. initial phase: isoniazid + rifampicin + pyrazinamide + ethambutol (2 months) 2. continuation phase: isoniazid + rifampicin (4 months)

retreatment

  1. isoniazid + rifampicin + pyrazinamide + ethambutol and streptomycin (2 months) 2. ioniazid + rifampicin + ethambutol (5 months)
137
Q

true or false

Treatment needs to be fully supervised (Directly Observed Therapy - DOT) in patients who cannot be relied upon to comply with the treatment regimen.

A

true

138
Q

what are the manifestations of gonococcus

A

cervicitis

urethritis

139
Q

neisseria genus is divided into two, what are they

A

gonorrhea → causing Epididymitis in mucosal epithelia

meningitidis → causing meningitis

140
Q

what is pelvic inflammatory disease?

A

inflammation of uterus and fallopian tubes

141
Q

what are complication of pelvic inflammatory disease

A

ectopic pregnancy

142
Q

what immune response is capable of killing all gonococcus genus

A

complement system

143
Q

how are gonococcus able to grow in large amounts in the blood stream?

A

they are surrounded by a capsule that enhances the organism’s ability to withstand complement mediated killing in the blood streaam

144
Q

what do meningicocci shed?

A

lipopolysaccharides, which reduce the release of tumor necrosis factor in the blood and CSF

145
Q

what is the main group of gram negative cocci?

A

neisseria

146
Q

what are facultative anaerobes?

A

use nitrites as electron acceptors and grow anaerbically

147
Q

which gonoccocus produces a respiratory disease

A

Moraxella catarrhalis

148
Q

true or false

humans are the only resevoir for gonococcus

A

true

149
Q

what would you need for gonococcus culture?

A

boiled blood

iron

vitamins

carbon dioxide

150
Q

what factors aid gonococcus in attachment

A

pili

surface proteins

lipooligosaccharides

151
Q

what is phase variation

A

genetic mechanism that enables bacteria to express or unexpress their surface adherence components/antigenic variation

152
Q

what is the difference between pili and opa in gonococcus

A

Pili and colony opacity-associated proteins (Opa) are surface-exposed structures of Neisseria gonorrhoeae. Pili can extend several micrometers from the gonococcal cell surface, while Opa proteins are integral parts of the outer membrane.

153
Q

how is pili of significance to gonococcus

A

Pili are inhibitory to phagocytosis of gonococci by polymorphonuclear cells

154
Q

why do gonococcus invade non ciliated epithelial mucosa of the fallopian tubes

A

because non ciliated epithelia possess microvili which aids in attachment, ciliary stasis, internalization, intracellular replication leading to exocytosis of dead cell

155
Q

what is gonorrhoea genital mucosal secretions composed of

A
  • IgG → leakage of antibodies from serum to mucos surface
  • IgA 1 / IgA 2 → help Neisseria evade opsonization not only by eliminating the presence of Fc fragments of IgA1 already bound but also by reducing the neutralizing ability of IgA1 antibodies by reducing their binding avidity.
156
Q

which molecule in gonococcus kills ciliated cells of fallopian tubes

A

lipopolysaccharides

157
Q

how is gonococcus internalized in the fallopian tubes?

A

microvili and nonciliated cells engulf bacteria by parasite directed endocytosis

158
Q

why is it that gonorrhea is often asymptomatic in women, but symptomatic in men

A

cervical cells have a pilus-mediated association with complement receptor 3 (CR3) which invades events that lead to epithelial colonization, contrarily, male urethra does not have pilus associated defence, thus it can be inflammatory

159
Q

what cells of the immune system kill gonorrhea and how?

A

complement → activating cr3

IgG/IgM antibodies → attack LOS of gonorrhea

160
Q

how does gonococcus become resistant

A

when LOS is altered by addition of terminal sialic acid molecule on short core carbohydrate chain causing the microorganism to camoflage and protect itself from serum

PH1123 Microbiology (9 decks)

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