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Y3 Medical Micro > L4 Bacteria, structure, function & taxonomy > Flashcards

L4 Bacteria, structure, function & taxonomy Flashcards

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USMLE® Step 1 flashcards
1
Q

what do unicellular microorganisms rely on

A

hosts

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2
Q

where do unicellular microorganisms live

A

free living

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3
Q

what is monera

A

single cell

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4
Q

what is protists

A

single cell

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5
Q

what is grouped in monera

A

prokaryotes

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6
Q

what are prokaryotes

A

eubacteria

archaeobacteria

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7
Q

what is grouped in protists

A

eukaryotes

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8
Q

what are eukaryotes

A

protozoa

algae/slime moulds

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9
Q

what is the structure of a typical bacterial cell

A 
pili
flagellum
outer membrane
cell wall
inner membrane 
ribosomes
genome of DNA folded and organised 
no nucleus/nuclear membrane
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10
Q

how does the bacteria move

A

flagellum for motility anchored in cytoplasmic membrane – needs energy from cytoplasmic membrane (electron transport chain)

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11
Q

where is the peptidoglycan

A

cell wall

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12
Q

do prokaryotes or eukaryote protist have nucleic acids

A

both do

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13
Q

do prokaryotes or eukaryote protist have structured nucleus

A

prokaryotes -

eukaryotes +

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14
Q

do prokaryotes or eukaryote protist have mitochondria

A

prokaryotes -

eukaryotes +

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15
Q

do prokaryotes or eukaryote protist have ribosomes

A

both do

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16
Q

do prokaryotes or eukaryote protist have cell membrane

A

both do

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17
Q

do prokaryotes or eukaryote protist have rigid PG cell wall

A

prokaryote +

eukaryotes -

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18
Q

do prokaryotes or eukaryote protist have mesosome

A

prokaryote +

eukaryotes -

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19
Q

do prokaryotes or eukaryote protist have ER/Golgi

A

prokaryote -

eukaryotes +

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20
Q

what is a mesosome

A

invagination of cytoplasmic membrane important for cell division to make daughter cells

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21
Q

what is the binomial system for naming bacteria

A

genus + species

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22
Q

why is bacterial taxonomy important

A 
handling info 
learning 
communication 
identification
evolution
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23
Q

what are the phenotypic characteristics

A 
morphology 
- macro/micro-scopic
biotyping - biochemical tests
serotyping
antibiogram patterns
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24
Q

macroscopic growth characteristics

A 
shape
margin
elevation
size
texture
appearance 
pigmentation
optical density
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25
Q

what is beta hemolysis

A

complete hemolysis = yellow no red on blood agar

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26
Q

what is alpha hemolysis

A

degraded partially, characteristic green/brown colour

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27
Q

microscopic growth characteristics

A

shape
size
staining
arrangement

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28
Q

what are the shapes of microscopic growth

A 
rod
club
coccus (round)
curved (vibrio)
spirillum 
spirochaete
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29
Q

what are the staining charactersitics

A

gram stain - true bacteria

acid fast stain - mycobacteria

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30
Q

how are the genotypic characteristics tested

A 
% GC ratios
DNA hybridisation 
chromosomal DNA fragment analysis
ribotyping 
MALDI_TOF
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31
Q

what is MALDI TOF

A

Matrix-Assisted Laser Desorption/Ionization-Time Of Flight
sample mixed in liquid matrix with solvent (maybe acid) break up any vegetative bacteria, crystallise and hit with a laser = desorbs the material, ionises it and put through a vacuum column and hit detector = mass spectra gram of the sample

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32
Q

what is ribotyping

A

extract DNA and break up enzymatically into smaller linear units and probs single stranded DNA that has been enzymatically broken up into ribosomal RNA genes that are unique to specific organisms - rRNA-based phylogenetic analyses

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33
Q

what is DNA hybridisation

A

species specific probes that are specific to specific bacteria = if makes ds then it is the organism that you think it is

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34
Q

what is the difference between gram + and - cell wall

A

gram + is thick

gram - is thin

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35
Q

how does a gram stain work

A

crystal Violet stain
gram’s Iodine (mordant, fixes crystal violet)
decoloriser
(alcohol/acetone)
(gram+ve PG too thick so not stripped)
safranin red (counter stain, gram-ve gets stained)

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36
Q

do gram + and gram - have an outer membrane

A

gram +ve has no outer membrane

gram -ve has got an outer membrane

37
Q

do gram + and gram - have and LPS (endotoxin)

A

gram +ve doesnt

gram -ve does

38
Q

do gram + and gram - have teichoic acid

A

gram +ve does

gram -ve doesnt

39
Q

do gram + and gram - sporulate

A

some strains of gram +ve do

gram -ve dont

40
Q

do gram + and gram - have a capsule

A

sometimes

41
Q

are gram + and gram - lysozyme sensitive

A

gram +ve are

gram -ve are not

42
Q

what is lysozyme function

A

hydrolyses PG

43
Q

which of the gram + and gram - are more susceptible to penicillin

A

gram +ve most susceptible

44
Q

what is teichoic acid interlinked with

A

PG

45
Q

what is LPS made up of

A

lipid A, outer core made of carbohydrate, O antigen

46
Q

what is the function of cell wall

A 
maintain rigidity, cell shape/structure
maintain osmolarity (prevent osmotic lysis)
survival - interacts with host membranes 
cell division - form cross wall separating 2 daughter cells
47
Q

what is a cell wall made up of

A

two disaccharide sugars - N-acetylglucosamine and N-acetylmuramic acidalternating

48
Q

what form are amino acids in - in cell wall

A

natural form of amino acid is L isomeric form

49
Q

where are D isomeric forms found

A

cell wall there is a D isomeric form only form in nature where D isoform is made

50
Q

how are adjacent stem peptides linked to the cell walls

A

linked directly by transpeptidase reaction (e.g. in E. coli) whereas in some gram positive have penta-glycine (5 glycine amino acids) form a cross bridge between adjacent stem peptides – where AB work

51
Q

how do antibiotics with beta lactam structure work

A

molecular mimic for the stem peptide amino acid, interact with pencillin binding protein or transpeptidase enzyme and prevent that enzyme binding to amino acids ion stem peptide to form cross bridge
no cross bridge = no PG effective structure no cell wall and bacteria die (bactericidal)

52
Q

how does vancomycin work

A

binds to terminal D-ala molecular inhibition - also prevents transpeptidation of adjacent stem peptides

53
Q

how does the bacterial cell wall synthesise

A

PG precursor synthesised inside cell
exported across cell membrane
site is created in existing wall by enzymic action (PBPs)
new nucleotide minus terminal D-ala is encorporated
cell ‘grows

54
Q

how are mycobacterium different

A

modified PG layer
covalently attached to arabinogalactan polymer
mycolic acid waxy coat - lipids
poor gram stain

55
Q

why cant mycobacterium be gram stained

A

arabinogalactan polymer

56
Q

how are mycobacterium stained

A

acid fast gram stain (Zeihl-Neelsen stain) - carbolfuchsin

57
Q

how are mycoplasma different

A

no cell wall

cell membrane has steroids from host membrane

58
Q

what are cell membranes generally like

A 
lipid bilayer - hydrophobic
no steroids (except mycoplasma)
ion transport and energy production (mitochondria)
mesosomes
electron transport
59
Q

what are spores like

A

cell survival in adverse conditions

desiccation, heat, starvation

60
Q

what are capsules for

A

protect against phagocytosis

61
Q

what are capsules

A

gelatinous material,polysaccharide/polypeptide

62
Q

what are flagella for

A

cell motility

63
Q

what are flagella like

A

1-20; peritrichous or polar

coiled in structure

64
Q

where are flagella

A

anchored into bacterial membrane

65
Q

what is the flagella protein

A

flagellin

66
Q

what do flagella do

A

chemotaxis

67
Q

how do flagella move

A

ATP driven motor membrane potential

68
Q

what are fimbriae like

A

smaller length and diameter than flagella

69
Q

how are fimbriae arranged

A

peritrichous arrangement

70
Q

are fimbriae or flagella coiled

A

only flagella are

71
Q

what is the fimbriae protein

A

pilin

72
Q

what is the sex pili

A

F plasmid

73
Q

what kind of infection do fimbriae cause

A

e. coli UTI

N.gonorrhoeae

74
Q

what is LOS

A

LPS with no O antigen

75
Q

what has LOS

A

neisseria

76
Q

what happens to LPS in cell

A

shed LPS into constituent moietys, lipid A = inflammatory response, activates cytokines for e.g. increased temp, create fever, organ failure through lack of blood flow

77
Q

which bacteria have porins

A

gram -ve

78
Q

which bacteria have pili

A

N.gonnorrhea

79
Q

what are the surface proteins in gram +ve

A 
afimbrial adhesins
protein F (Strep. pyogenes)
80
Q

what do gram +ve bacteria cause on infection

A

inflammatory response

cytokines/shock

81
Q

what affect the growth of bacteria

A 
O2/CO2
temperature
water 
pH
light
osmolarity (5-12%)
82
Q

what are the nutritional requirements for bacterial growth

A

carbon and nitrogen source
inorganic salts
organic compounds

83
Q

what are inorganic salts bacteria require for growth

A

Fe/Na/K/P/Ca/Mg

84
Q

what are auxotrophs

A

can’t make essential nutrient have to get from environment

85
Q

what is the medical relevance of cell wall synthesis

A

antibiotics

86
Q

what is the medical relevance of capsules

A

vaccines

87
Q

what is the medical relevance of cell membranes

A

antibiotics

vaccines

88
Q

what is the medical relevance of ribosomes

A

antibiotics

89
Q

what are monera and protists

like

A

unpaired chromosomes

no nucleus

Y3 Medical Micro (16 decks)

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