Microbiology Flashcards
1
Q
What is the name of the first oxygen producing micro-organisms?
A
Cyanobacteria
2
Q
What 3 things is all life classified as?
A
Bacteria, Archaea, Eukarya
3
Q
What was Pasteurs hypothesis?
A
Microorganisms present in putrefying material were descendants of those already present in the material or that were are carried in on dust particles in air
4
Q
Knowledge that life does not arise spontaneously allows?
A
- Prevention of food spoilage
- Prevention of infections during operations
- Understanding of the causes of infectious diseases
5
Q
Who helped in the prevention of food spoilage and when?
A
Louis Pasteur (fermentation, pasteurisation) 1864
6
Q
Who helped in the prevention of infections during operations?
A
Lister (aseptic technique) 1867
7
Q
Who helped in the understanding of the causes of infectious diseases?
A
Koch (Germ theory of disease & Koch’s postulates) 1876
8
Q
What experiment was defined as definitive proof for biogenies?
A
Swan neck flask
9
Q
What were Koch’s postulates?
A
- The suspected pathogen must be present in all cases of disease and absent from healthy animals
- Suspected pathogen must be grown in pure cultures
- Cells from a pure culture of the suspected pathogen must cause disease in a healthy animal
- The suspected pathogen must be reisolated and shown to be the same as the original
10
Q
What did Hooke do?
A
First observed “cells”
11
Q
What did Van Leeuwenhoek do?
A
Observed live micro-organisms
12
Q
How did Karl Woese discover archaea?
A
He looked at the ribosomal DNA and recognised it was very different to that of bacteria
13
Q
Features of a bacterial cytoplasm.
A
- Thick, semi-transparent and elastic
- 80% water
- Contains all the molecules required for life
14
Q
Features within the bacterial cytoplasm.
A
- The nucleiod (DNA)
- Ribosomes (site of proteins synthesis composed of RNA and protein
15
Q
Features of a bacterial cell membrane.
A
- A thin structure inside the cell wall and enclosing the cytoplasm
- Consists of a phospholipid bilayer
- Contains selective carrier proteins
- Acts as a semi-selective barrier that regulates the uptake of nutrients
16
Q
Features of bacterial cell wall.
A
- Very rigid to protect cell from rupturing
- Antigenic, often contains toxic molecules and is a common site for antibiotic action
- Two types differentiated by gram stain
17
Q
How is the strength of a bacterial cell wall provided?
A
A mucopeptide called peptidoglycan which is unique to bacteria
18
Q
Composition of cell wall in gram negative bacteria from inside to outside
A
Cytoplasm, Inner membrane, Cell wall, Outer membrane, Lipopolysaccharide (LPS)
19
Q
Composition of cell wall in gram positive bacteria from inside to outside
A
Cytoplasm, Inner membrane, Cell wall, Teichoic Acids
20
Q
What do lipopolysaccharides do?
A
Otherwise known as endotoxin. Important virulence factor for evading phagocytosis and a barrier to certain antibiotics
21
Q
What is teichoic acid?
A
Long anionic polymers that thread through the thick, multi layer of highly cross-linked peptidoglycan.
22
Q
Describe the capsule of a bacteria
A
Firmly attached and highly organised
23
Q
Describe the slime layer of a bacteria
A
Unorganised and loosely attached
24
Q
What do flagella do?
A
Help a bacteria move by rotation
25
Describe flagella
Long whip like structure required for motility
26
3 Components of flagella
1. Long spiral filament made of many proteins including flagellin and acts as a propeller
2. Attached to a hook which can transmit torque
3. Attached to motors that drive their rotation
27
What protein is the filament made of?
Flagellin
28
Structure of pili/fimbriae
Hair-like appendages, shorter, stronger and thinner than flagella
29
Functions of pili.
- Involved in forming biofilms and attachment of cells
| - Used for DNA transfer, called conjugation
30
What is an endospore?
A dormant form of the bacterium which is highly resistant to adverse environmental conditions
31
What is a broth and its purpose?
A liquid media
| For enrichment of certain bacteria, obtaining large numbers of bacteria and for performing growth curves
32
What is agar and its purpose?
Solid media:
- Usually first step of bacterial identification
- Observe the colonial morphology which aids ID
- Assess purity of the culture
33
What is sloppy agar and its purpose?
Semi-solid agar
- Demonstrating mobility
- Preserving bacteria
34
What are the 5 steps of staining for gram +/-
1. Fixation
2. Crystal violet
3. Lugol's iodine
4. Decolourisation
5. Safranin
35
What are the end colour results for gram +/- staining?
Gram positive - purple
| Gram negative - pink
36
Structure of filamentous fungi
- Consist of hyphae
| - Some hyphae contain cross walls (septa) which divide them internally into distinct uni-nucleate units
37
What is hyphae?
Thin, thread-like filaments
38
Structure of non-filamentous fungi
Unicellular, round or oval cells
39
What is dimorphism?
The ability of a fungus to exist in both morphological forms
40
What are heterotrophs?
They don't make their own food, they obtain their nutrients from pre-formed sources of organic carbon
Fungi are heterotrophs
41
What are saprotrophs?
Primary decomposers
| Fungi are saprotrophs
42
What do fungi store food as
Glycogen
43
3 mechanisms of asexual reproduction in fungi
1. Hyphae fragmentation
2. Spore production
3. Budding (only in yeast)
44
3 examples of fungi as a pathogen
1. Superficial infections (dermatomycoses)
2. Subcutaneous fungal infections
3. Systemic mycoses
45
What are superficial infections with examples?
Also referred to as dermatomycoses, it's infections of the outer layer of the skin, the hair and nails
Examples = athletes foot, ringworm
46
What are subcutaneous fungal infections?
Infections that usually occur in deeper layers of the skin and sometimes even reach the underlying bone
Examples = chromoblastomytosis and mycetoma
47
What is systemic mycoses?
Infection that often occurs via the inhalation of spores in individuals with weakened immune systems
Examples = Thrush and histoplasmosis
48
Describe fungi as a symbiont : mycorrhizae
- Mutualistic relationship between fungus and plant root
- Fungus functions like a root by growing in the soil and absorbing nutrients while the plant provides it with sugar for energy
49
Properties of ectomycorrhiza
-Common in temperate forest ecosystems
-Fungus - ascomycota and basidiomycota
Between root cells
50
Properties of Arbuscular mycorrhiza
- Common in grasslands and tropical ecosystems
- Fungus - zygomycota
- Invades root cells
51
Describe fungi as a symbiont : Lichens
- First forms of life to colonise bare rocks/soil
| - Acts as barometer for air quality - change in lichens = change in pollution
52
What is chimera and explain this is protozoa
Derived from two or more genetically different types
| Protozoa are formed from two prokaryotes and kept the characteristics of them both
53
Give examples of how protozoa are hard to classify
1. The genus Euglena has chloroplasts and flagella
2. Giardia have two nuclei and no mitochondria
3. Entamoeba have many nuclei and no mitochondria
54
What are the 4 main groups of protozoa and what are they characterised by?
1. Ciliates
2. Apicomplexa
3. Flagellate
4. Amoebae
Characterised by : movement, nutrition and reproduction
55
What do microorganisms need energy for?
- Grow and move
- Reproduce
- Maintain cell structures
- Defend themselves against threat
56
What are the by products of anaerobic respiration?
Lactate and acetaldehyde (then to alcohol)
57
What is an obligate aerobe?
Cannot survive without oxygen
58
What is a facultative aerobe?
Primarily anaerobic but can respire using oxygen
59
What is a obligate anaerobe?
Cannot grow in the presence of oxygen (vegetative cells)
60
What is a facultative anaerobe?
Primarily aerobic but can respire anaerobically
61
What is a microaerophillic organism?
Required oxygen but can only tolerate a small amount
62
What is the main source of carbon?
Atmosphere and organic compounds
63
What is an autotroph?
An organism that produces its own food using light, water, CO2/ other chemicals
64
How does an autotroph acquire carbon?
Via CO2
65
What is a heterotroph?
An organism that eats other plants or animals for food or energy/nutrients
66
How do heterotrophs acquire carbon?
Amino acids, fatty acids, organic acids, sugars, nitrogenous bases, aromatic compounds
67
What does chemoautotrophic mean?
Organisms that are able to synthesis they own organic molecules from the fixation of CO2 straight from sources
68
What does chemoheterotrophic mean?
Organisms that cannot synthesis their own organic materials and therefore need to break down readily synthesised carbon in order to acquire it
69
Photoautotrophic meaning
Organisms that can synthesise its own food from inorganic material using light as a source of energy
70
Photoheterotrophic meaning
Organism that uses light for energy but cannot use CO2 as its sole carbon source and therefore uses organic compounds from the environment
71
What are some of the benefits of viruses?
- Control animal population
- Kill pests
- Oncolytic - destroy cancer cells
72
What are zoonoses?
Diseases that can cross species boundaries
73
How are viruses zoonoses?
Vectors
74
How were viruses discovered?
Through a filtration process that would normally filter out bacteria so it was concluded that they're smaller than bacteria
75
Characteristics of viruses?
- Small (20-300nm - too small to be seen with light microscope)
- No metabolism
- Obligate intracellular parasites (need hosts)
- Dormant on surfaces but replicate when they penetrate a host cell using hosts synthesising machinery
- Genetic information usually encoded as one linear OR circular piece of DNA/RNA
- Contain protein coat surrounding nucleic acid
76
What are some methods used for culturing animal virus?
- Embryonated eggs
- Living animals
- Cell cultures
77
What is the plaque method?
Sample mixed with phages
Monolayer of cells-detect number of cells destroyed
Viral infection = lysed cells = clearings
Clearings = Plaque
78
Why don't antibiotics work against viruses and what is used instead?
Viruses have no metabolism
Instead antiviral medicines are used but they usually interfere with viral multiplication which can interfere with the host cell and be toxic
79
Attenuated vaccination meaning?
Weakened
80
Inactivated vaccination meaning?
Dead
81
Subunit vaccination meaning?
Only antigenic (stimulated immune system)
82
Conjugate vaccination meaning?
Antigen and protein to aid its recognition
83
Nucleic acid vaccination meaning?
Injected DNA/mRNA
84
How do most viruses come to be?
Self-assemble spontaneously
85
Where is the structural information of a virus stored?
Proteins
86
What is the capsid?
A protein coat that surrounds the genetic material (genome)
87
What is a capsomer?
Clusters of proteins that make up the capsid (EM)
88
What is the envelope of a protein?
Lipid bi-layer surrounding the capsid in some viruses
89
What are peplomers?
Glycoproteins in the EM
90
What is multimeric?
Multiple peptide chains
| Capsomers and peplomers are both multimeric
91
What is a complete virus particle called?
Virion
92
What does the capsid need to be protected from and why?
Nucleic acids are fragile and needed to be protected from:
- UV radiation
- Extreme pH (gastrointestinal tract)
- Dehydration (exposure to air)
- Enzymatic attack (bodily fluids)
93
Functions of the capsid?
- Packaging nucleic acid
- Host cell recognition
- Genomic material delivering
94
Structures of capsid
- Linear array of capsid proteins can coil to helix to protect genome
- Triangular unit can form individual faces of a larger structure
95
What is the most common structure of capsid?
Icosahedral - 20 faces of equilateral triangles
96
What are the host cells machinery?
Enzymes, ribosomes, tRNA's
97
What are the host cells raw materials?
Nucleotides, amino acids and energy
98
Describe the use of non-structural proteins in viral replication
- Enzymes needed to replicate viral genome
- Needed immediately in small amounts (upon infection)
- Required only inside infected cell
- Will not become part of the virus
99
Describe the use of structural proteins in viral replication
- Needed to form progeny particles
- Needed in large quantity
- Only needed after genome is replicated
- Needed later to package the genome
e. g. spike proteins, lipid bi-layer
100
Describe positive sense RNA
Has the same structures of mRNA: methylated cap, start codon, stop codon, open reading frame etc.
101
Describe negative sense RNA
- Is the complement of mRNA sense
- Has a sequence related to the + by rules of base pairing but is not a reversal of it
- Lacks all recognised features of mRNA
- Cannot be translated - doesn't make proteins
- Can be copied (transcribed) making a complimentary (positive sense mRNA) strand that might be translated
102
Which cells do viruses attack?
1. Susceptible cell
| 2. Permissive cell
103
What is meant by susceptible cell?
Entry allowed by having the right cell attachment factors, receptors or co-receptors
104
What is meant by permissive cell?
Viral replication is supported, all the right tools and building blocks are there for a given virus
105
What is the endocytic route of virus attack?
(no membrane) Clathrin mediated endocytosis and penetration
106
What is the non-endocytic route of virus attack and the 4 steps (HIV as example)?
(present membrane) fusion at cell surface to release capsid into cell
1. HIV glycoprotein binds to receptor (CD4)
2. HIV glycoprotein binds to co-receptor (CCR5 mainly)
3. HIV envelope and plasma membrane fuse together
4. HIV capsid released and disassemble in cytoplasm
107
What is a mesophile?
Organisms that grow best at body temperature (37ºC) - most pathogens thrive at body temperature
Ranges from 10-50ºC
108
What is a thermophile?
Thrives between 40-70ºC
| Above 65ºC, only prokaryotes survive
109
What is a hyperthermophile?
Thrives between 65-110ºC
| Mainly archaea thrive at very high temperatures (no bacteria above 95ºC
110
What is a psychotroph?
Optimum grown rate at approx 20ºC
| Range is 0-30ºC
111
What is a psychophile?
Optimin growth is approx 10ºC
| Range is -10-20ºC
112
What is an acidophile?
Tolerates low pH
| pH 0-6
113
What is a neutrophile?
pH 5.5-8
114
What is an alkaliphile?
pH 8-14
115
What is a halophile?
Organisms that require salt, specifically NaCl
116
What is an osmophile?
Adapted to environments with high osmotic pressure like high sugar concentrations
117
What is a xerophile?
Organisms adapted to living in low Aw
118
What is a hypotonic environment?
Low salt so water moves into the cell - cell may burst
119
What is an isotonic environment?
No net movement of water
120
What is an hypertonic environment?
High salt/sugar so water moves out of the cell - cell might shrink
121
What is a microaerophillic?
Requires oxygen but at lower levels than atmospheric oxygen
122
What is aerotolerant?
Cannot use oxygen for growth but are unaffected by the presence of it
