microbiology Flashcards
1
Q
what are the different prokaryotes?
A
-bacteria
-archaea
2
Q
what is bacteria?
A
-contains all the known disease causing bacteria and most of the bacteria found in the soil, water,animals and other environments
3
Q
what is archaea?
A
-mostly anaerobes and they thrive in extreme environments like hot springs,freezing water, highly salty, acidic and alkaline environments
4
Q
what do eukaryotic organisms include?
A
-algae
-fungi
-protozoa
-cells of macroorganisms
5
Q
what did eukaryotes evolve and gain?
A
-mitochondria
-chloroplasts
-internal membranes
-bound nucleus by endosymbiosis
6
Q
compare the DNA in prokaryotes and eukaryotes
A
p-DNA not enclosed in membrane, circular and supercoiled
e-discrete nucleus with nuclear membrane,linear genetic material
7
Q
compare the histone and protein content in prokaryotes and eukaryotes
A
p-DNA not associated with histones and has low protein content
e-DNA has high histone content and non histone proteins
8
Q
compare the organelles in prokaryotes and eukaryotes
A
p-no organelles
e-organelles
9
Q
compare how prokaryotes and eukaryotes divide
A
p-binary fission
e-mitosis and meiosis
10
Q
what ribosomes do prokaryotes and eukaryotes have?
A
p-70S ribosomes
e-80S ribosomes
11
Q
describe the cell wall in prokaryotes and eukaryotes
A
p-complex cell wall
also form biofilms
e-simple cell wall If present
12
Q
what do we see microbial diversity of in prokaryotes and eukaryotes?
A
-structure
-function
-behaviour
-adaptation
13
Q
what are biofilms?
A
clusters of microorganisms that stick to non-biological surfaces
14
Q
what does phototrophic bacteria lead to?
A
phototrophic bacteria in cells lead to photosynthesis
15
Q
how can phylogenetic relationships be calculated?
A
-gene sequencing of 16S or 18S ribosomal RNA
-amplify the gene of the ribosomal sequence
-computer comers sequences and counts every position where the is a difference
-ED (evolutionary distance)
-construction of a tree where the length of the line is proportional to the ED
16
Q
why are viruses not present on the phylogenetic tree?
A
because they do not contain ribosomes ands can’t be analysed in the same way
17
Q
describe viruses…
A
-they have very small genomes and are very diverse
-there is no highly conserved molecular ID for them
18
Q
what does it mean when viruses infect humans or bacteria?
A
-if they infect humans,they could not have evolved before them
-if they infect bacteria then they probably appeared as bacteria
19
Q
what was taxonomy and classification of microorganisms based on originally?
A
phenotypic and metabolic behaviour
20
Q
what was used to classify organisms in the past?
A
G-C content
21
Q
how are microorganisms classified now?
A
by genotyping
-microorganisms are named using the binomial nomenclature system after Linnaeus
-the Genus name is first (always with a capital letter) followed by the species name (no capital)
-the names are always written in italics or underlined
22
Q
where do groups of related cells live?
A
-in a habitat or niche
23
Q
how are ecosystems formed?
A
by associating with other populations in microbial communities
24
Q
what is antagonism?
A
-the production of toxins and antibiotics
25
what do microbial populations compete for?
nutrients and riches
26
what is cooperation in microbial populations?
one group of microorganisms provide nutrients for others
27
how many cells and microorganisms do humans have?
-humans have 10₁₃ cells and 10₁₆
microorganisms associated with them
28
where do microbial populations live?
water, soil,plants,animals and form the microflora of their habitat
29
what type of relationship may microbial populations have with their host?
mutualistic, saprophytic or parasitic
30
what is bacteria measure in?
microns 1um=0.001mm
31
what is the size of bacteria?
bacteria range in size from 0.2um (chlamydiae) up to 10um
-the smallest are at the limit of resolution of the light microscope
32
what are the different shapes (morphology) that bacteria can come in?
-cocci
-bacilli
-ovoid
-tapered
-curved
-spiral
-hyphae-like structures
33
what are the different cellular arrangements bacteria can have?
-clusters
-chains
-diploid
-tetrads
-palisades
34
what are the different growth characteristics that can affect bacteria?
-speed
-morphology on selective and non-selective media
-atmosphere
-temperature
35
what can affect bacterial classification?
-cellular arrangements
-motility
-presence or absence
36
what can we use to classify bacteria?
-biochemical profiles
-serological tests
-metabolic end products as detected by HPLC,GLC
-genetic analysis by rRNA typing-GC content
-staining characteristics:gram,acid fast
37
what do cell envelopes provide?
-protection from osmotic lysis
-protection from host defences
-shape and rigidity
-semi-permeable barrier
-may form up to 1/3 of the dry weight of the bacterium
38
what can the prokaryotic cell envelope be defined as?
-the complex of membranes and associated with macromolecules which together form the boundary between the inside and the outside of the cell
-they are the interface between bacteria and the diverse spectrum of environments that they inhabit
39
state the three types of bacterial cell walls?
-gram positive
-gram negative
-acid-fast
40
compare gram-positive and gram negative cell walls
-gram-positive-has a high internal osmolarity and red a thicker cell wall
-gram-negative-thinner but more complex cell wall
41
what do acid-fast walls contain?
complex lipids
42
why does gram-staining show differentiation?
- because there are differences due to the physical nature of the bacterial cell walls
43
what does peptidoglycan and iodine do? (gram-staining)
-peptidoglycan acts as a permeability barrier preventing the loss of the initial stain, it is crystal violet
-iodine is the 2nd solution to be added, it is mordant and so acts as a coordination comlex
44
what does iodine being a mordant mean?
-it acts as a trapping agent that complexes with the crystal filet making the crystal violet-iodine complex clump stay contained in thick layers of peptidoglycan in the cell walls
45
what happens in the decolorisation step of gram-staining?
-it shrinks the pores of the thick peptidoglycan and the CV-I complex is retained
-gram negative bacteria have a thin layer of peptidoglycan with less cross-linking and larger pores
-the CV-I complex is removed more easily through the G-cell wall
46
give a summary of the steps in gram-staining...
-fixation
-crystal violet
-iodine treatment
-decolorization
-counter stain safranin
47
how can cell walls be removed?
by being in osmotically stabilising solutions
48
what happens to gram positive and gram negative organisms without walls?
-gram positive organisms become spherical protoplasts
-gram negatives become spheroplasts
their survival depends o keeping them in hypertonic solutions of sucrose
49
what are L forms?
variants that have lost the ability to synthesise a cell wall
50
what does a cytoplasmic membrane contain?
-ion pumps to maintain membrane potential and synthetic enzymes
-the mesosome,a coiled portion of the membrane
51
what does the mesosome do?
acts as an anchor to bind and pull apart daughter chromosomes during cell division
52
what is the structure of the peptidoglycan (murein)?
-it is common to all types of bacterial cell wall
-has 2 sugar derivatives connected in beta1-4 linkages: N-acetyl glucosamine (NAG) &
N-acetyl muramic acid (NAM)
53
what is the repeating structure that peptidoglycan forms called?
-glycan terapeptide
54
what gives glycol chains their rigidity?
-they are connected by peptide cross links of 4 amino acids
55
what does cross linking in gram-positive bacteria involve?
-a peptide interbridge
56
what does each interbridge in S.aureus consist of?
-5 molecules of the amino acid glycine connected by peptide bonds (peptapeptide)
57
what are the peptidoglycan specifics?
-they form a mesh like exoskeleton but is porous enough to allow diffusion for metabolites
-it is essential for survival in hostile conditions
-it. can interfere with phagocytosis and is mitogenic for lymphocytes and has pyrogenic activity
58
what can the beta1-4 bond in peptidoglycan be degraded by?
-lysozymes
59
what does amino acids does tetrapeptide contain?
-both D and L amino acids
-the first 2 amino acids may vary for different organisms
-3rd amino acid is essential for cross linking
60
what do D amino acids include?
-lysine and diaminopimelic acid (DAP)
-this links to D-alanine in the position 4 of another chain
61
what does the precursor form of the peptidoglycan have?
-an extra D-ala which is released during the cross linking step
-prefabricated subunits are assembled on the inside of the cell and brought to the surface by a large phospholipid called bactoprenol and attached to the existing structure
62
what does peptidoglycan form in gram-positive bacteria?
-multiple layers and often cross linked in 3 dimensions to give strong rigid cell walls
63
what are the additional components of peptidoglycan?
-techoic acid (acidic polysaccharide) is present in the cell wall
-also contains glycerophosphate or ribitol phosphate residues
-it is negatively charged and this contributes to overall negative charge of cell surface
64
what are lipoteichoic acids?
-glycerol containing acids bound to membrane lipids of gram positives
-they mediate attachment to host cells
65
what may be attached to the hydroxyls of ribose or glycerol?
-sugars,choline or D-alanine providing antigenic determinants and they may determine the serotype of bacteria
66
what do proteins do?
form part of the cell wall
67
what does the M protein of Group A streptococcus do?
present as fine processes called fimbriae
68
what does the protein A of S aureus do?
-binds to the Fc region of igG
-competes with neutrophil receptors for the Fc region of opsonising antibodies
69
how are gram-negative cell walls?
-thin,but comlex
-has a cytoplasmic membrane and thin layer of peptidoglycan
-in the periplasmic space between the CM and the inner surface of the outer membrane
70
what does the periplasmic space of gram-negative cell walls have?
a variety of hydrolytic enzymes necessary to break down large macromolecules for metabolism
71
what enzymes are in the periplasmic place?
-proteases,phosphatases,;ipases,nucleases,carbohyrate degrading enzymes
72
what are the virulence factors in pathogenic bacteria?
-collagenases,hyluronidases,proteases and beta-lactamase
73
what other things does the periplasmic space contain?
-components of chemotaxis system which senses the environment outside of the cell and sugar transport systems and binding proteins
74
what is the function of the outer membrane that is unique to gram-negative prokaryotes?
-maintain s structure and forms permeability barriers to large molecules e.g lysosymes
-provides protection from adverse environmental conditions such as the human digestive system
-the outer edge of the membrane is different from other biological membranes
75
76
what is LPS?
-an amphiphatic molecule which is an outer membrane component of gram negative bacteria and is known as a lipopolysaccharide
-it is also known as an endotoxin
77
what does the LPS do?
-it is a powerful stimulator of the immune response and it activates B cells, macrophages and it is stimulated to release IL1 and 6 tumour necrosis factor
-can lead to fever and if large amounts are present it can cause septic shock and multi organ failure
78
what are the 3 structural sections of the LPS?
-lipid A
-core polysaccharide
-O polysaccharide
79
what does lipid A of the LPS do?
-its responsible for endotoxic activity
-very toxic to the host
-released in large quantities when cells die
-con lists of 6 fatty acid chains and 2 glucosamine residues
80
what does the core polysaccharide part of the LPS do?
-it is branched and contains 9-12 sugars
-it contains unusual sugar 2 kept-3-deoxy-octanate (KDO)
-it is the core region for many species of bacteria
81
what does the O antigen of the LPS do?
-it is a long linear polysaccharide of 50-100 repeating saccharide units of 4-7 sugars per unit
-it distinguishes serotypes of bacterial species
82
what are membrane pores?
-porin proteins that form channels in the membrane
-there are roughly 100 on the cell surface
-they have a diameter of 10 angstrom
83
what do membrane pores do?
-act as transport proteins for larger metabolites including:
maltose, oligosaccharides, Vitamin B12, nucleotides
-they are permeable to hydrophilic molecules and less to hydrophobic molecules
-they are less sensitive to antibiotics
84
what is the function of the cell wall?
-it gives bacteria a characteristic shape,protection,transport mechanisms, aid pathogenicity
85
what are the advantages to man if the cell wall?
classification, provide selective toxicity for anti-microbials
86
what is mycobacterium?
-bacteria that is considered as acid fast bacteria since it has a peptidoglycan layer attached to an arabinogalactan polymeric is surrounded by a wax-like lipid coat of myopic acid, cord factor and wax D
-it is acid fats staining and interferes with phagocytosis
87
what is the flagella?
-long thin appendages that originate from the cytoplasmic membrane
-they extend through the cell wall into the surrounding medium
-they enable bacteria to be mobile
88
where is the flagella observed mostly in?
-gram-negative rod shaped bacteria
-gram positive rods
89
what are the features of the flagella?
-they are very thin (20nm)
-they are not visible by light microscope unless stained
-they vary in number /arrangement on bacterial surface
-bacterial characteristic is used during classification
90
what is the flagella composed of?
flagella (protein)
around 30-40 kDa (kilodalton)
91
what are the different types of flagella arrangement and give examples for each?
-monotrichous-vibrio cholerae
-lophotrichous-bartonella bacilliformis
-amphitrichous-sprillum serpens
-peritrichous-escherichia coli
92
what is the fundamental structure of the flagella?
-it is helical
-there is a constant distance between 2 wavelengths
-it is constant for a given organism
-it is composed of protein subunit of flagellin
93
what are the three main components of a flagellum?
-the motor-basal body
-the hook-consists of a single class of proteins at the base of the flagellum connecting the filament to the motor
-the filament
94
what are the flagella antigens?
-flagella antigens are typed by their O (LPS) and H (flagellar) antigens
-there are >2000 serotypes with different O and H antigens
95
how does the flagella show phase variation?
they have the ability to differentially express the protein antigen as either phase 1 or phase 2
96
what is the structure of the flagella basal body?
-it is anchored in the cytoplasmic membrane and cell wall
-there is a small rod passing through a system of rings
-2 Mot proteins are anchored either side of the MS ring
-there are Fli proteins
-multiple rings are present in the gram negative bacteria
97
where are the different rings that are present in gram-negative bacteria?
-an outer ring in OM/LPS
-one in peptidoglycan
-one in the cytoplasmic membrane
-one in the cytoplasm
98
what do the 2 motor proteins on the flagella basal body do?
-they drive the flagellar motor causing a torque that rotates the filament
99
how does energy relate to the flagella basal body
energy is supplied by the passage of protons from the outside cell into they cytoplasm via the basal body mot complex,there are nearly 1000 protons for a single proton.
100
what 2 bacterial genera produce highly resistant endospores?
-bacillus and clostridia
-these enable them to survive under adverse environmental conditions for long periods of time
101
how long can endospores survive?
-for up to 30yrs in soil
-these are: B anthracis,C.tetanus,C.perfringens
102
what structure do endopores have?
-spherical or oval structures
-the size, shape and location of the spores within the stationary phase of vegetative cells are helpful for their identification
-they appear as non-staining refractive areas within the cell
103
what are endospores resistant to?
drying, heat,pressure,chemical disinfectants
104
what are endospores killed by?
heating to 120*c for 15-20mins
105
what is the formation of endospores stimulated by?
environmental conditions where there is:
lack of nutrients
change of temp
redox potential
106
what are the three stages of endospores formation?
-activation
-germination
-outgrowth
107
what happens in the activation stage of endospores formation?
-it is activated in vitro by heating at a sub-lethal but elevated temp
108
what happens in the germination stage of the formation of endospores?
they germinate when placed in nutrients:
-there is a loss of resistance to heat and chemicals
-loss of calcium dipicolinate and cortex components
-acid-soluble spore proteins degraded
109
what does germination lead to?
-a conversion back to the vegetative cell rapidly
110
what happens when their is an outgrowth of endospores?
-there is visible swelling as a result of water uptake and synthesis of new RNA, proteins and DNA
-the cell emerges from the broken spore and begins to divide
111
112
what is the pili and fimbriae?
-fine hair like filaments on the surface of many gram negative bacteria
-they are not involved in mobility
-the pili is generally longer
113
how much protein is the fimbriae composed of?
20kDa
114
what do the pili and fimbriae do?
-they are involved in the attachment of bacteria to host cells
-they bind to lectins on cell surfaces e.g sugar binding proteins
-they give tissue specificity
115
what do the pili and fimbriae being fragile structures mean?
-the bacteria within a human host are constantly losing and reforming fimbriae
-this aids in the evasion of the immune system
116
what can gonorrhoea do to the pili/fimbriae?
-it can change their structure
117
continue from slide 65
