Week 3 Diebel - Microbial Structure & Bacterial Growth & Physiology Flashcards
1
Q
What are three ways bacteria cause disease?
A
- Toxin production: release toxins > cause illness
- Host immune response: response of host > cause illness
- Bacterial proliferation and invasion: growth and spread of bacteria > cause damage > lead to illness
2
Q
What are three ways viruses cause disease?
A
- Cytopathic effect: infection disrupts cell physiology > cell disease & death
- Host immune response: host responds > illness
- Tumorigenesis: infection promotes uncontrolled proliferation of infected cells (oncogenic viruses)
3
Q
Who is Antonie Van Leeuwenhoek?
A
1632-1723
“Father of Microbiology”
came up with first simple microscope
4
Q
What is Louis Pasteur (1822-1895) famous for?
A
His work on spontaneous generation.
He disproved the theory 200 years after Leeuwenhoek and Hooke.
Led to the development of methods for controlling the growth of microorganisms.
5
Q
What is the Spontaneous Generation Hypothesis?
A
The hypothesis that living organisms can originate from nonliving matter.
6
Q
How did Louis Pasteur disprove the spontaneous generation hypothesis?
A
“Swan Neck Experiment”
compared the growth of microorganisms in one flask containing sterile broth that was exposed to the air and one containing sterile broth that was not exposed to the air.
***Proved that all life came from pre-existing life forms.
7
Q
What did Robert Koch (1843-1910) demonstrate in his studies on infectious disease?
A
The link between microbes and infectious diseases, i.e. the “Germ Theory of Disease”
8
Q
What are the four modes of transmission of infectious diseases?
A
- Person-to-person
- Zonotic
- Soil-born
- Common source
9
Q
What are three types of person-to-person transmission of infectious disease?
A
- Air-born
- Direct contact or contact with a product of another person
- Sexually transmitted infections
10
Q
What is Zonotic transmission of infectious disease?
A
Vector-born disease
i.e. animals, arthropods, etc.
11
Q
What is common source transmission of infectious disease?
A
Diseases transmitted through water sources, food born illnesses.
ex. cholera
12
Q
What two conditions did Robert Koch identify the the causative agents of?
A
Anthrax and Tuberculosis
13
Q
What are Koch’s postulates?
A
- The suspected pathogen must be present in ALL cases of the disease and absent from healthy animals.
- The suspected pathogen must be grown in pure culture.
- 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.
14
Q
What are the pro’s and con’s of Koch’s Postulates?
A
Pro’s:
-Link certain diseases with specific pathological organism.
Con’s:
- Requires small animal model system to test pathogen in.
- Not all pathogens have an animal model (e.g. HIV).
- Some pathogens act differently in carrier than host (e.g. malaria and misquito).
15
Q
What is the “Gene Theory of Disease”?
A
- Microbial infections that lead to disease can be viewed as an arms race for replication that in the purest sense is related to the survival of one set of genetic information at the expense of another.
- Microbiology and disease = a war for resources
- who is best at replicating their genetic information over others
16
Q
What is a virulence factor?
A
- Any molecule of a microorganism that aides in its ability to establish and maintain a pathogenic infection.
- Help to acheive: invasion, colonization, immunosuppression, obtain nutrition, exit
17
Q
Describe the Pathway of Infection (7 steps)
A
- EXPOSURE to pathogens
- ADHERENCE to skin or mucosa
- INVASION through epithelium
- COLONIZATION and GROWTH production of virulence factors
- INVASIVENESS: further growth at original and distant sites
- TOXICITY: toxin effects are local or systemic
- TISSUE DAMAGE & DISEASE when you finally know you are sick
18
Q
Describe Frederick Griffith’s experiment with bacteria and transformation.
A
- Rough strain (nonvirulent) bacteria > mouse LIVES
- Smooth strain (virulent) bacteria > mouse DIES
- Heat-killed smooth strain > mouse LIVES
- Rough strain (nonvirulent) + Heat-killed smooth strain >>> MOUSE DIES!!!!
19
Q
What did Frederick Griffith’s experiment suggest about bacteria?
A
Bacteria are capable of transferring genetic information.
***Transformation***
20
Q
What are the five classifications of microorganisms that can cause disease?
A
- Viruses
- Bacteria
- Helmnets (worms)
- Fungus
- Protozoa
(plus prions)
21
Q
What is a disease fact sheet?
A
Gives the following about a disease:
- Disease Name
- System(s) affected
- Most likely causative microorganism
- General disease information
- Differential diagnosis
- Treatment
22
Q
Why do we stain bacteria?
A
- Most bacteria are colorless
- Helps to classify bacteria
- Improves contrast
- Staining dyes are positively charged organic compounds that are attracted to the negative charge under bacterial plasma membrane
- It’s easy!
23
Q
How do you prepare a gram stain?
A
- Prepair a Smear: spread culture in thin film over slide and air dry
- Heat Fixing: Pass slide through flame to heat fix
- Staining: flood slide with crystal violet stain for 1 minute
- Add iodine solution for one minute
- Decolorize with alcohol rinse for 20 seconds
- Counterstain with safranin for 1-2 minutes
24
Q
Describe the six bacterial morphologies.
A
- Coccus (sphere)
- Bacilli (rod)
- Spirillium (rigid, gm (-), helical/spiral)
- Spirochete (thin, spiral shape)
- Budding and Appendaged Bacteria (stalk+hypha)
- Filamentous bacteria
25
What are four features of a Gram Positive (+) Cell wall?
Purple!
1. Inner cytoplasmic membrane
2. Thick peptidoglycan cell wall
3. Teichoic acids
4. Smooth outer appearance
26
What are six features of Gram Negative (-) cell wall?
Pink!
1. Lipopolysaccharide
2. Outer membrane
3. Thin peptidoglycan cell wall
4. Periplasm
5. Inner cytoplasmic membrane
6. Appears bumpy
27
What are five differences between prokaryotic cells and eukaryotic cells?
1. Nucleoid with aggregated mass of DNA in proks, and membrane-enclosed nucleus in euks
2. Circular DNA in proks, linear DNA in euks
3. Naked DNA in proks, chromosome/histone proteinated DNA in euks
4. Plasmid in proks
5. Membrane bound organelles in euks
28
What are common structures in prokaryotic and eukaryotic microbial cells? (four)
1. Cytoplasm
2. Cytoplasmic Membrane
3. Ribosomes
4. Usually a cell wall...
29
What is a plasmid?
Circular extrachromosomal genetic elements (DNA), nonessential for growth, found in prokaryotes.
\*\* Contains virulence factors \*\*
30
How is the peptidoglycan in the cell wall arranged?
Peptide cross-links bonded to sugar groups with glycosidid bonds.
(built in two different directions with two different molecules)
Polysaccharide backbone with branching peptides and various interbridge connections.
X-axis: glycosidic bonds
Y-axis: peptide bonds
31
What is binary fission?
Method in which microbial growth and replication occurs:
1. Cell elongation
2. Septum formation
3. Completion of septum, formation of cell wall, cell separation.
32
What type of growth patterns do microbial populations show?
Exponential growth
33
What step of peptidoglycan synthesis and cell division does Penicillin block?
Penicillin binds to and blocks the activity of the enzyme required for the transpeptidation reaction (DD-transpeptidase).
\*\*Thus Selectively Toxic!
34
What are three mechanisms by which bacteria can cause disease?
1. Toxicity
2. Host Immune Respones
3. Colonization & Proliferation
(Gray area between the last two)
35
How do you measure a microorganism's virulence?
By determining its lethal dose in a model organism.
(ex. highly virulent organisms need a smaller numer of cells to kill 50% of model organism)
36
How is virulence determined according to Dr. Diebel?
Determined by the "Gene Theory of Disease".
"Determined by the genes available to aid in the steps of pathogenesis, including mechanisms such as invasiveness, immune evasion, and toxicity."
37
What are some basic properties of Exotoxins?
* **proteins** secreted out of bacterial cell
* generally **heat liable**
* bind to **specific** cell receptors or structures
* often **highly toxic**, sometimes fatal
* highly immunogenic, body can neutralize toxin with antitoxin
* does not produce fever
38
What are some basic properties of endotoxins?
* **Structural component** of the cell, usually Lipopolysaccharide-lipoprotein complexes
* extremely **heat-stable**
* **non-specific** binding or action
* cause fever, diarrhea, & vomiting
* **weakly toxic**, rarely fatal
* immune response not sufficient to neutralize toxin
39
What are some of the examples of exotoxins discussed in class?
* Cytolytic exotoxins - protein secreted from bacterial cell that forms holes in a cell membrane exposing contents \>\> cells die!
* Hemolysins (alpha, beta, & gamma)
* AB Toxins - B toxin binds to membrane and release A toxin into the cell to hurt cell
* Neurotoxins - blocks release of neurotransmitter or release of glycine to allow muscle relaxation
* Superantigen - activates any local T-cells by binding MHC class II to SEH receptor
40
What was the example of endotoxins discussed in class?
* LPS - released on cell lysis and Lipid A causes toxic effect \> fever
41
What were some of the virulence factors discussed in the Salmonella example in class?
* Toxins - enterotoxin, endotoxin, & cytotoxin
* Adherence - cell surface polysaccharide O antigen, flagellar H antigen, & fimbriae
* Plasmid - drug resistance genes
* Host-immune evasion - pathogenicity islands that integrate info into host cell
42
What are the three layers of the immune system?
1. Physical barriers (ex. skin)
2. Innate Immune Response ("built-in" immunity)
3. Adaptive Immune Response ("memory" immunity)
43
What is the innate immune system?
* non-inducible, pre-existing ability to recognize and destroy pathogens and their associated products
* responds by phagocytosis (facilitated by complements)
* recognizes PAMPs (pathogen-associated molecular patterns)
* interferons mediate an early response to viral infection
44
What are the major players of the innate immune system?
Responds to environment
* Monocytes
* Dedritic cell
* Macrophage
* Granulocytes
* Neutrophil
* Mast cell
45
What is the complement system?
* 20 serum proteins
* Key component of innate immunity!
* Overall goal it to controll inflammation by trying to wipe out antigens.
* Lysis
* Phagocyte chemotaxis
* Opsonization (coat bacteria)
46
How do interferons limit the spread of certain viral infections?
Use a self-sensing mechanism:
infected cell will send out a signal
47
What responds to PAMPs?
Innate Immune Receptors called:
PRRs (pattern recognition receptors)
-they recruit macrophages, and later neutrophils
48
When does the innate immune system usually stop infections?
Before they can cause symptoms.
49
What happens if the innate immune system is evaded and/or fails to clear an infection?
It initiates the adaptive immune system response!
(Phagocytes are responsible for innate immunity as well as initiating adaptive immunity)
50
Simply put, what is adaptive immunity?
The acquired ability to recognize and destroy an individual pathogen.
51
What specialized group of cells link the innate and adaptive immune systems by taking up and processing antigens so they can be recognized by T-cells?
Antigen Presenting Cells (APCs)
-bridge between innate and adaptive systems
52
What kind of cells do APCs activate?
T-cells
53
What small signalling proteins do APCs produce?
Cytokines
54
What are the major playersin the adaptive immune system?
1. T-cells
2. B-cells
3. Plasma cells (produce antibodies)
55
How does the antibody bind to the antigen?
* Each antibody binds to a restricted part of the antigen called the epitope.
* Fab region = antigen binding site (arms of the Y)
* Fc region binds to the Fc receptor of a phagocyte
56
How do plasma cells know when to make clones of antigen-specific lymphocytes?
B-cells bind to antibody bound to antigen
stimulates B-cell proliferation/maturation
causes plasma cells to make memory cells
57
What is passive immunity?
Nonimmune person's acquisition of pre-formed immune cells or antibodies via the transfer of cells or antibodies from an immune person.
ex. newborns with maternal IgG antibodies
58
What is active immunity?
Acquiring an infection that initiates an adaptive immune response.
- exposure to antigens
- production of antibodies and T-cells
ex. Vaccines!
59
What are antibodies?
immunoglobulin molecules that recognize antigens
60
What are the three classifications of hemolysins?
* Alpha hemolytic:
* hemolysin \> only damages RBCs, not destroy
* Beta hemolytic:
* hemolysin \> completely destroys RBCs
* Gamma hemolytic:
* no hemolysin, does not affect RBCs
61
What is a pathogenicity island?
The integration of prophage information into a host cell.
Responsible for invasion, systemic disease, and host-immune evasion.
62
What are the four categories of eukaryotic viruses (nucleic acid)?
1. ssDNA
2. dsDNA
3. ssRNA
4. dsRNA
63
What are the four categories of viral capsids?
1. Icosohedral
2. Capsomeres (naked)
3. Complex capsid (helical, segmented)
4. Lipid membrane (enveloped)
64
What are the four layers of a eukaryotic virus?
1. Envelope
2. Tegument
3. Capsid
4. Nucleic acid
65
What are the structural features of bacterial viruses (bacteriophages)?
* Head
* ssDNA, dsDNA, ssRNA, or dsRNA
* Collar
* Tail
* Endplate
* Tail pins
* Tail fibers
66
What two classes in the Baltimore Classification System use dsDNA (+/-)?
Class I & Class VII
(transcription of minus strand to produce (+)mRNA)
67
What class of the Baltimore Classification System uses ssDNA (+)?
Class II
- synthesizes dsDNA and transcribes minus strand to produce (+) mRNA
ex. Parvoviruses
68
What class of the Baltimore Classification System uses dsRNA (+/-)?
Class III
transcription of minus strand produces (+) mRNA
ex. Reovirus
69
What class in the Baltimore Classification System uses ssRNA (+)?
Class IV
synthesize ssRNA (-) and transcribe minus strand to produce mRNA (+)
ex. Picornaviruses
?????
70
What class of Baltimore Classification System uses ssRNA (-)?
Class V
Transcription of minus strand produces mRNA (+)
ex. Orthomyxoviruses
71
What class of Baltimore Classification System uses ssRNA (+)?
Class VI
Uses reverse transcription to produce dsDNA intermediate, then transcription of minus strand produces mRNA (+)
ex. Retrovirus
72
What are the five general steps to any viral replication?
1. Virion must attach to potential host cell
2. Injection of nucleic acid
3. Synthesis of nucleic acid and protein
4. Assembly and packaging of new viruses
5. Release (lysis)
73
What does DdDp do?
DNA dependent DNA polymerase
makes copies of DNA from DNA
74
What does DdRp do?
DNA dependent RNA polymerase
responsible for transcription (DNA \> RNA)
75
What does RdRp do?
RNA dependent RNA polymerase
makes copies of RNA from RNA
\*\*Drug targets for treatment of viral infection because they are not part of host cell machinery
76
What does RdDp do?
RNA dependent DNA polymerase
(a.k.a. Reverse Transcriptase)
Make DNA from RNA
77
Describe Class I viral replication.
* uncoated dsDNA enters nucleus
* becomes circular
* uses host DdRp \> mRNA (+)
* mRNA travels to host cytoplasm
* host ribosomes translate
\*\*\*Replicate genome using host machinery
ex. Herpesviruses
78
Describe Class IV viral replication.
* ssRNA (+) enters cytoplasm
* finds host ribosome
* immediately translated
* synthesizes viral RdRp to replicate genome
79
What are the primary lymphoid orgnas that function in the development of the immune system?
Bone marrow & Thymus
80
What kind of cells does the bone marrow produce that are self-renewal?
Hematopoietic stem cells
81
What two types of cells generate from Hematopoietic stem cells with the help of IL3 and IL3/GM-CSF?
Lymphoid Pro & Myeloid Pro
82
What two types of precursor cells do Lymphoid Pro cells differentiate into?
B-cell Pro (bone-marrow)
T-cell Pro (thymus)
83
T-cell Pro cells differentiate into what two specialized T-cells?
CD4+ ("helper" T-cells)
CD8+ ("cytotoxic" T-cells)
84
Myeloid Pro differentiates into what four precursor cells?
* GM Pro (Monocytes/Neutrophils)
* Basophil Pro (Basophils)
* Erythroid Pro (RBCs)
* Megakaryocyte (Platelets)
85
Myeloid Pro differentiates directly into what specialized cell type?
Dendritic cells
86
What are the key structural features of Hepatitis C Virus?
ssRNA (+)
Capsid protein surrounding nucleic acid
No tegument
Glycoprotein envelope
87
What does the HCV nucleic acid do as soon as it enters the nucleus?
+ssRNA finds a ribosome
IRES serves as initiation sequence (no 5' cap)
eIF3 (translation factor) helps protein synthesis
synthesize replication and packaging machinery and RdRp in ER membrane
protease cuts proteins apart \>\> then they assemble!
88
What toll-like receptor is responsible for sensing HPC?
TLR3
89
What does TLR3 toll-receptor do in response to sensing HPC pass through the PM?
Initiates signal transduction that ultimately turns on interferon beta
(IRF3 becomes phosphorylated \> dimerizes \> transcription factor for interferon beta)
90
What does interferon beta do in response to transcription and activation by TLR3?
Turns on signal pathway that shuts down metabolic processes and replication in the cell.
91
What happens if Toll-Like Receptor 3 misses recognition of the HCV when it enters the cell?
Innate Immune Systems "back up" plan takes over.
A protein complex on the mitochondria recognize the dsRNA of HCV and activates the phosphorylation of IRF3 \> dimerizes \> forms transcription factor \> makes interferon beta!!!
92
93
What are gene expression strategies for bacteria?
* only one RNA polymerase
* Polycistronic
* no cap, no tail, no intron
* shine delgarno initiation sequence
* 30S & 50S = 70S
* Transcription and translation happen together in the cytoplasm
* has operons
94
What are the gene expression strategies for Eukaryotes?
* 3 different RNA polymerases (I, II, & III)
* RNA Pol II responsible for transcription
* Monocistronic
* 5'cap, Poly A tail, introns
* ribosome requires initiation factors
* 40S + 60S = 80S ribosome
* NO OPERONS
95
What are the gene expression strategies for viruses?
Depends on Baltimore classification system.
* use host RNA polymerase or RdRp
* Uses host ribosomes
* variable mRNA
* may have 5'cap, Poly A tail, IRES
* occasionally has operon
96
How do DNA binding proteins control bacterial gene expression?
* interact with DNA sequence
* bind to major grove
* multiple outcomes
* catalyze specific rxn (ex. transcription)
* block transcription
* activate transcription
97
What is quorum sensing?
Mechanism by which bacteria assess their population density.
Bacteria produce autoinducers to upregulate gene expression by binding to activator proteins.
98
Describe homologous recombination.
A clipped piece of DNA from a donor becomes incoorporated into a recipient piece of DNA.
(requires sequence similarity and necessary enzymes to integrate DNA)
99
Describe Transformation.
Cell dies \> chromosome breaks down \> piece of free DNA attaches to recipient cell \> becomes incorporated
(Cells that are capable of being transformed = competent)
100
Describe transduction.
Transfer of DNA from one cell to another mediated by a bacteriophage.
(Generalized & Specialized)
101
What is the difference between Generalized and Specialized Transduction?
Generalized packages DNA derived from any portion of the host genome into the mature virion,
where specialized takes DNA from a specific region of the host to integrate into the virus genome.
102
What is the difference between a F+ cell and and F- cell?
F+ has an F plasmid (donor), F- does not have a plasmid (recipient).
103
What is a cell posseing an integrated F plasmid in the genome called?
Hfr: High frequency of recombination
alterations in cell properties
104
What are transposable elements?
Discrete segments of DNA that move as a unit from one ocation to another within other DNA molecules.
(Two types: conservative & replicative)
105
What is the difference between conservative and replicative mechanisms of Transposition?
Conservative transposon is excised from one location and reinserted at a second loaction.
Replicative: a new copy of transposon is produced and inserted at a second location.
106
What are selective medias?
Contains compounds that selectively inhibit growth of some microbes but not others.
107
What is differential media?
Contains an indicator, usually a dye, that detects particular chemical reactions occuring during growth.
(How does it grow?)
108
