BIO 2200 Exam 4 Flashcards
(172 cards)
1
Q
What is genetic engineering?
A
using in vitro techniques to alter genetic material in the laboratory
2
Q
What do restriction enzymes do?
A
recognize specific DNA sequences and cut DNA at those sites; protect cell from invasion from foreign DNA
3
Q
How many classes of restriction enzymes are there? What does type II do?
A
three; Type II cleave DNA within their recognition sequence and are most useful for specific DNA manipulation
4
Q
What do modification enzymes do?
A
Chemically modify nucleotides in restriction recognition sequence; protect cell’s DNA for restriction enzymes
5
Q
What happens during gel electrophoresis? How does is it do that? What is the gel made of? What end does the DNA travel towards? What are the gels stained by and why?
A
It separates DNA molecules based on size. Electrophoresis uses an electrical field to separate charged molecules. Gels are usually made of agarose, a polysaccharide. Nucleic acids migrate through gel toward the positive electrode due to their negatively charged phosphate groups. Gels are stained with ethidium bromide so DNA can be visualized under UV light.
6
Q
How can the size of DNA be determined?
A
Size of fragments can be determined by comparison to a standard
7
Q
What is a restriction map?
A
a map of the location of restriction enzyme cuts on a segment of DNA
8
Q
What is nucleic acid hybridization?
A
base pairing of single strands of DNA or RNA from two different sources to give a hybrid double helix
9
Q
What is a nucleic acid probe?
A
segment of single-stranded DNA that is used in hybridization and has a predetermined identity
10
Q
What is southern blot? northern blot?
A
Southern blot is a hybridization procedure where DNA is in the gel and probe is RNA or DNA. Northern blot is when RNA is in the gel.
11
Q
What is molecular cloning?
A
isolation and incorporation of a piece of DNA into a vector so it can be replicated and manipulated
12
Q
What are the three main steps of gene cloning?
A
1) Isolation and fragmentation of source DNA
2) Insertion of DNA fragment into cloning vector
3) Introduction of cloned DNA into host organism
13
Q
What are most vectors derived from?
A
plasmids or viruses
14
Q
What is DNA ligase?
A
enzyme that joins two DNA molecules (works with sticky or blunt ends)
15
Q
What is a gene library? What process creates it?
A
Gene library is a mixture of cells containing a variety of genes. Shotgun cloning creates gene libraries by cloning random genome fragments.
16
Q
What is site-directed mutagenesis? What can it do?
A
Site-directed mutagenesis is performed in vitro and introduces mutations at a precise location. Can be used to assess the activity of specific amino acids in a protein.
17
Q
What is cassette mutagenesis?
A
When DNA fragment are cut, excised, and replaced by a synthetic DNA fragment (DNA cassettes or cartridges).
18
Q
What is gene disruption? What can it cause?
A
Gene disruption is when cassettes are inserted into the middle of the gene. Gene disruption causes knockout mutations (gene becomes inoperative).
19
Q
What are reporter genes? What are some examples?
A
Reporter genes encode proteins that are easy to detect and assay. Examples are lacZ, luciferase, GFP genes.
20
Q
What are gene fusions?
A
When promoters or coding sequences of genes of interest are swapped with those of reporter genes to elucidate gene regulation under various conditions.
21
Q
What are 4 reasons plasmids make good cloning vectors?
A
1) Small size –> easy to isolate DNA
2) Independent origin of replication
3) Multiple copy number: get multiple copies of cloned gene per cell
4) Presence of selectable markers
22
Q
What is a common cloning vector? What does it contain?
A
pUC19 is a common cloning vector. It is a modified ColE1 plasmid that contains ampicillin resistance and lacZ genes. It also contains polylinker (multiple cloning site) within lacZ gene.
23
Q
What is blue/white screening?
A
It is used to see what has foreign DNA inserted. Blue colonies do not have vector with foreign DNA inserted, while white colonies have foreign DNA inserted.
24
Q
What is insertional inactivation? What does it cause?
A
It is when the lacZ gene is inactivated by insertion of foreign DNA. This inactivated lacZ then cannot process Xgal, which inhibits the blue color to develop.
25
What are 5 characteristics of ideal hosts for cloning vectors?
1) Capable of rapid growth in inexpensive medium
2) Nonpathogenic
3) Capable of incorporating DNA
4) Genetically stable in culture
5) Equipped with appropriate enzymes to allow replication of the vector
26
What are 3 examples of ideal hosts for cloning vectors?
Escherichia coli, Bacillus subtilis, Saccharomyces cerevisiae
27
What are 3 advantages and 2 disadvantages of E. coli being a host for cloning vector?
Advantages are that it is well-developed in genetics, has many strains available , and is the best known bacterium. Disadvantages are that it is potentially pathogenic and the periplasm traps proteins.
28
What are 4 advantages and 2 disadvantages of B. subtilis being a host for cloning vector?
Advantages are that it is easily transformed, nonpathogenic, naturally secretes proteins , and endospore formation simplifies culture. Disadvantages are that it is genetically unstable and genetics are less developed than in E. coli.
29
What are 4 advantages and 2 disadvantages of Saccharomyces cervisiae (eukaryote) being a host for cloning vector?
Advantages are that it is well-developed in genetics, nonpathogenic , can process mRNA and proteins , and easy to grow. Disadvantages are that plasmids are unstable and will not replicate most bacterial plasmids.
30
What is transfection? How is it done?
Transfection is introduction of DNA into mammalian cells. Originally done through phagocytosis of DNA by host cell. It can also be done using microinjection, electroporation, or gene gun.
31
What are shuttle vectors?
vectors that are stably maintained in two or more unrelated host organisms
32
What do expression vectors allow the experimenter to do?
allow experimenter to control the expression of cloned genes
33
What are 4 characteristics of expression vectors?
1) Based on transcriptional control
2) Allow for high levels of protein expression
3) Strong promoters (lac, trp, tac, trc, lambda PL)
4) Effective transcription terminators are used to prevent expression of other genes on the plasmid
34
What are 3 problems that can occur when mRNA produced must be efficiently translated?
1) Bacterial ribosome binding sites are not present in eukaryotic genomes
2) Differences in codon usage between organisms
3) Eukaryotic genes containing introns will not be expressed properly in prokaryotes
35
What are 5 examples of vectors that exist for cloning in eukaryotic cells?
Yeast artificial chromosomes (YACs), DNA virus SV40, adenovirus, vaccinia virus, and baculovirus
36
What do integrating vectors do?
Integrate into host chromosome and are stably maintained in cell
37
Why does the bacteriophage lambda make a good cloning vector?
1) Well-understood biology
2) Can hold larger amounts of DNA than most plasmids
3) DNA can be efficiently packaged in vitro
4) Can efficiently infect suitable host particles
38
What are the 5 steps to cloning with lambda?
1) Isolating vector DNA from phage particles and cutting it with the appropriate restriction enzyme
2) Connecting the lambda fragments to foreign DNA using DNA ligase
3) Packaging of the DNA by adding cell extracts containing the head and tail proteins
4) Infecting E. coli cells and isolating phage clones by picking plaques
5) Checking the recombinant phage for the presence of foreign DNA
39
What are cosmids? Why are they good cloning vectors (4)?
Cosmids are plasmid vectors containing the cos site from the lambda genome. They can be packaged into lambda virions, inserts as large as 50 kilo bases are accepted, avoids necessity of transforming E. coli, and phage particles are more stable than plasmids.
40
What are 3 specialized vectors for genome analysis?
Bacteriophage M13, bacterial artificial chromosomes (BACs), and yeast artificial chromosomes (YACs)
41
What does the bacteriophage M13 do and what does it have?
clone DNA up to 5 kilo bases and contains lacZ for blue/white screening
42
What is the bacterial artificial chromosome constructed from and what is the host for it?
Constructed from the F plasmid and host for a BAC is generally a mutant strain of E. coli
43
What can yeast artificial chromosomes do and how to they replicate? What is similar to YACs?
YACs can accommodate 200-800 kilo bases of cloned DNA and they replicate like normal yeast chromosomes. Human artificial chromosomes are similar to YACs.
44
What is industrial microbiology? What did it originate from?
Uses microorganisms, typically grown on a large scale, to produce products or carry out chemical transformation. Originated with alcoholic fermentation processes.
45
What are 5 properties of a useful industrial microbe?
produces spores or can be easily inoculated, grows rapidly on a large scale in inexpensive medium, produces desired product quickly, should not be pathogenic, and amenable to genetic manipulation
46
What are 7 products of industrial microbiology?
microbial cells, enzymes, antibiotics, steroids, alkaloids, food additives, and commodity chemicals
47
What are commodity chemicals and what are some examples?
Inexpensive chemicals produced in bulk and include ethanol, citric acid, and many others
48
What is a primary metabolite? secondary metabolite?
Primary metabolites are produced during the exponential growth (alcohol), while secondary metabolites are produced during the stationary phase.
49
What are 5 characteristics of secondary metabolites?
They are not essential for growth, formation depends on growth conditions, produced as a group of related compounds, often significantly overproduced, and often produced by spore forming microbes during sporulation.
50
What do secondary metabolites require for production? Give an example. What do starting materials arise from?
Secondary metabolites are often large organic molecules that require a large number of specific enzymatic steps for production. For example, synthesis of tetracycline requires at least 72 separate enzymatic steps. Starting materials arise from major biosynthetic pathways.
51
What are fermentors?
A fermentor is where the microbiology process takes place. Any large-scale reaction is referred to as a fermentation (most are aerobic processes).
52
What must be done with industrial fermentors (4 things)?
They must be closely monitored during production run, growth and product formation must be measured, environmental factors must be controlled and altered as needed
(including temperature, pH, cell mass, nutrients, and product concentration), and
data on the process must be obtained in real time.
53
What is a scale-up? What are the steps?
The transfer of a process from a small laboratory scale to large-scale commercial equipment. Flask to laboratory fermentor to pilot plant to commercial fermentor.
54
What is the major task of a biochemical engineer?
they need to require the knowledge of the biology of producing organism and the physics of fermentor design and operation
55
What are antibiotics? What kind of metabolites are they? What are they produced by?
Antibiotics are compounds that kill or inhibit the growth of other microbes. They are typically secondary metabolites. Most antibiotics in clinical use are produced by filamentous fungi or actinomycetes.
56
How are antibiotics discovered?
Still discovered by laboratory screening. Microbes are obtained from nature in pure culture and then they are assayed for products that inhibit growth of test bacteria.
57
What is the cross-streak method used for?
The cross-streak method is used to test new microbial isolates for antibiotic production. Most isolates produce known antibiotics and most antibiotics fail toxicity and therapeutic tests in animals.
58
What is the time and cost of developing a new antibiotic?
Time and cost of developing a new antibiotic is approximately 15 years and $1 billion. It involves clinical trials and U.S. FDA approval.
59
What type of antibiotics are penicillins? What type of metabolite is penicillin production? Production only begins after what?
Penicillins are beta-lactam antibiotics. Penicillin production is typical of a secondary metabolite. Production only begins after near-exhaustion of carbon source. High levels of glucose repress penicillin production.
60
Production of what is second only to antibiotics in terms of total pharmaceutical sales?
vitamins; Vitamin B12 is produced exclusively by microorganisms. Riboflavin can also be produced by microbes.
61
What are amino acids used as (3) and what are 3 examples?
Amino acids are used as feed additives in the food industry, as nutritional supplements in nutraceutical industry, and as starting materials in the chemical industry. Examples are glutamic acid (MSG), aspartic acid and phenylalanine, and
lysine (food additives).
62
What are exoenzymes? What can they do?
Exoenzymes are enzymes that are excreted into the medium instead of being held within the cell. They are extracellular and they can digest insoluble polymers such as cellulose, protein, and starch.
63
Why are enzymes useful in industrial microbiology?
Enzymes are useful as industrial catalysts because they produce only one stereoisomer and have high substrate specificity.
64
What are enzymes produced from?
fungi and bacteria
65
What are bacterial proteases used in and what are they isolated from? Amylases and glucoamylases?
Bacterial proteases are used in laundry detergents (can also contain amylases, lipases, and reductases). They are isolated from alkaliphilic bacteria. Amylases and glucoamylases are commercially important because they produce high-fructose syrup.
66
What are extremozymes? What are they produced by?
Extremozymes are enzymes that function at some environmental extreme (pH or temperature). They are produced by extremophiles.
67
What are three ways to immobilize an enzyme? What are immobilized enzymes used in?
Three ways to immobilize an enzyme are bonding of enzyme to a carrier,
cross-linking of enzyme molecules, and enzyme inclusion. They are used in the starch processing industry.
68
What does wine come from? How big are the fermentors in which wine fermentation occurs and what are they made of? What is the difference between white wine and red wine?
Most wine is made from grapes. Wine fermentation occurs in fermentors ranging in size from 200 to 200,000 liters. Fermentors are made of oak, cement, glass-lined steel, or stone. White wine is made from white grapes or red grapes that have had their skin removed. Red wine is aged for months or years, while white wine is often sold without aging.
69
What is brewing? What is used to produce beer? What are the two main types of brewery yeast strains?
Brewing is the term used to describe the manufacture of alcoholic beverages from malted grains. Yeast is used to produce beer. Two main types of brewery yeast strains are top fermenting (ales) and bottom fermenting (lagers).
70
How are distilled alcoholic beverages made? What are some examples?
Distilled alcoholic beverages are made by heating previously fermented liquid to a temperature that volatilizes most of the alcohol. Examples include whiskey, rum, brandy, vodka, and gin.
71
How many liters of ethanol are produced yearly for industrial purposes? How is it used?
>50,000,000,000 liters of ethanol are produced yearly for industrial purposes. It is used as an industrial solvent and gasoline supplement.
72
What is biotechnology?
use of living organisms for industrial or commercial applications
73
What are genetically modified organisms (GMO)? What does genetic engineering allow? How is this achieved?
Genetically modified organism is an organism whose genome has been altered. Genetic engineering allows expression of eukaryotic genes in prokaryotes. This is achieved by cloning the gene via mRNA or finding the gene via the protein.
74
What 3 problems can occur if protein synthesis occurs in a foreign host?
1) Degradation by intracellular proteases
2) Toxicity to prokaryotic host
3) Formation of inclusion bodies
75
What was the first human protein made commercially by genetic engineering?
Insulin was the first human protein made commercially by genetic engineering.
76
What is somatrophin? How is cloned? What does recombinant bovine somatrophin (rBST) do?
Somatotropin is a widely produced growth hormone. it is cloned as cDNA from the mRNA. Recombinant bovine somatotropin (rBST) is commonly used in the dairy industry. It stimulates milk production in cows.
77
What is polyvalent vaccine?
a single vaccine that immunizes against two different diseases
78
What is a vector vaccine?
Vaccine made by inserting genes from a pathogenic virus into a relatively harmless carrier virus (e.g., vaccinia virus)
79
What is a subunit vaccine?
Contain only a specific protein or proteins from a pathogenic organism (e.g., coat protein of a virus).
80
How is a viral subunit vaccine prepared?
1) Fragmentation of viral DNA by restriction enzymes
2) Cloning of viral coat protein genes into a suitable vector
3) Provision of proper conditions for expression (promoter, reading frame, and ribosome-binding site)
4) Reinsertion and expression of the viral genes in a microbe
81
What is a DNA vaccine (genetic vaccine)?
Vaccine that uses the DNA of a pathogen to elicit an immune response
82
What is gene miming? How is this done?
The process of isolating potentially useful novel genes from the environment without culturing the organism. To do so, DNA (or RNA) is directly isolated from the environment and cloned into appropriate expression vectors, and the library is screened for activities of interest.
83
What is a transgenic organism?
An organism that contains a gene from another organism
84
What is pathway engineering?
The process of assembling a new or improved biochemical pathway using genes from one or more organisms (indigo)
85
What are transgenic animals useful for (3)?
Producing human proteins that require specific post translational modifications, medical research, and improving livestock and other food animals for human consumption.
86
What does the gene therapy do?
introduces a functional copy of a gene to treat a disease caused by a dysfunctional version of the gene
87
What does the use of recombinant DNA technology and conventional genetic studies allow for?
The use of recombinant DNA technology and conventional genetic studies allows for the localization of particular genetic defects to specific regions of the genome.
88
How can plants can be genetically modified?
Through electroporation, particle gun methods, and use of plasmids from bacterium Agrobacterium tumefaciens.
89
What does the Ti plasmid do? What is the segment of the Ti plasmid that is transferred to the plant called?
The Ti plasmid, coming from A. tumefaciens, is responsible for virulence. The Ti plasmid contains genes that mobilize DNA for the of to the plant. The segment of the Ti plasmid that is transferred to the plant is called the T-DNA.
90
What is sterilization?
The killing or removal of all viable organisms within a growth medium
91
What is inhibition?
Effectively limiting microbial growth
92
What is decontamination?
The treatment of an object to make it safe to handle
93
What is disinfection?
Directly targets the removal of all pathogens, not necessarily all microorganisms
94
What is the most widely used method of controlling microbial growth? How does it work?
Heat sterilization; high temperatures denature macromolecules
95
What is decimal reduction time?
amount of time required to reduce viability tenfold
96
Some bacteria produce resistant cells called what?
endospores; they can survive heat that would rapidly ill vegetative cells
97
What is the autoclave? What does it do and what kills the things?
The autoclave is a sealed device that uses steam under pressure. It allows temperature of water to get above 100 degrees Celcius. The pressure does not kill things, the high temperature does.
98
What is pasteurization? Why is it different than sterilization?
Pasteurization is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids. It is different than sterilization because it does not kill all the organisms.
99
What can UV do?
UV has sufficient energy to cause modifications and breaks in DNA. UV is useful for decontamination of surfaces.
100
What is ionizing radiation?
It is electromagnetic radiation that produce ions and other reactive molecules.
101
What are the sources of radiation sterilization? What is radiation sterilization used for?
Sources of radiation include cathode ray tubes, X-rays, and radioactive nuclides. Radiation is used for sterilization in the medical field and food industry.
102
What is radiation sterilization approved by? What are some examples of food that may be irradiated?
Radiation is approved by the WHO and is used in the USA for decontamination of foods particularly susceptible to microbial contamination. Hamburger, chicken, spices may all be irradiated.
103
How does filter sterilization work?
Filtration avoids the use of heat on sensitive liquids and gases. Pores of a filter are too small for organisms to pass through but they allow liquid or gas to pass through.
104
What is an example of a depth filter?
An example of a depth filter is a HEPA filter.
105
What are membrane filters? What can it be accomplished by? What is an example?
Membrane filters function more like a sieve. Filtration can be accomplished by a syringe, pump, or vacuum. A type of membrane filter is the nucleation track (nucleopore) filter.
106
What is the minimum inhibitory concentration? What does it vary with?
Minimum inhibitory concentration (MIC) is the smallest amount of an agent needed to inhibit growth of a microorganism. It varies with the organism used, inoculum size, temp, pH, etc.
107
What is disc diffusion assay?
Antimicrobial agent added to filter paper disc and then that disc is placed on a lawn of bacteria. It creates a zone of inhibition.
108
What are the two categories chemical antimicrobial agents can be divided into?
1) Products used to control microorganisms in commercial and industrial application (chemicals in foods, air-conditioning cooling towers, textile and paper products, fuel tanks)
2) Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces (Sterilants, disinfectants, sanitizers, and antiseptics)
109
Who studied selective toxicity? What is it?
Paul Ehrlich studied it. Selective toxicity is the ability to inhibit or kill a pathogen without affecting the host.
110
What is one of the first antimicrobial drugs?
Salvarsan
111
What are growth factor analogs?
Growth factor analogs are structurally similar to growth factors but do not function in the cell.
112
Who discovered sulfa drugs and what do they do?
They were discovered by Gerhard Domagk in the 1930s and they inhibit growth of bacteria (sulfanilamide is the simplest)
113
What is isoniazid and what does it do?
It is a growth analog effective only against Mycobacterium. It interferes with the synthesis of mycolic acid.
114
What do nucleic acid base analogs come from?
Nucleic acid base analogs have been formed by the addition of bromine or fluorine.
115
What are quinolones?
Quinolones are antibacterial compounds that interfere with DNA gyrase (e.g., ciprofloxacin).
116
What type of antimicrobial agents are antibiotics? How much of antibiotics are useful?
Antibiotics are naturally produced antimicrobial agents. Less than 1% of known antibiotics are clinically useful.
117
What are broad-spectrum antibiotics?
Broad-spectrum antibiotics are antibiotics that are effective against both groups of bacteria
118
What are one of the most important groups of antibiotics of all time? What are some examples?
Beta-Lactam antibiotics are one of the most important groups of antibiotics of all time. Include penicillins, cephalosporins, and cephamycins.
119
Who discovered penicillins? What are they primarily effective against? What is effective against gram-negative bacteria? What do they target?
They were discovered by Alexander Fleming. Primarily effective against gram-positive bacteria. Some synthetic forms are effective against some gram-negative bacteria. Target cell wall synthesis
120
What are cephalosporins produced by? What are they similar to? What are they commonly used to treat?
They are produced by fungus Cephalosporium. Same mode of action as the penicillins. Commonly used to treat gonorrhea.
121
Many antibiotics effective against Bacteria are produced by what?
bacteria
122
What are amino glycosides? What are examples?
Aminoglycosides are antibiotics that contain amino sugars bonded by glycosidic linkage. Examples are kanamycin, neomycin, and amikacin.
123
What type of antibiotics are macrolides? Give an example? In general, what does it come from?
Broad-spectrum antibiotic that targets the 50S subunit of ribosome.
An example is erythromycin. Comes from prokaryotes.
124
How many rings does tetracycline have? What is it used in? What does it inhibit? In general, what does it come from?
Four rings; Widespread medical use in humans and animals; It has a broad-spectrum inhibition of protein synthesis and inhibits functioning of 30S ribosomal subunit; Comes from prokaryotes
125
What does Daptomycin come from? What is it used to treat? What does it do?
Comes from prokaryotes; also produced by Streptomyces; It is used treat gram-positive bacterial infections and it forms pores in cytoplasmic membrane.
126
What do protease inhibitors do?
inhibit the processing of large viral proteins into individual components
127
What do fusion inhibitors do?
prevent viruses from successfully fusing with the host cell
128
What two categories of drugs successfully limit influenza infection?
Adamantanes and Neuraminidase inhibitors
129
What are interferons?
Interferons are small proteins that prevent viral multiplication by stimulating antiviral proteins in uninfected cells
130
Why do fungi pose special problems for chemotherapy?
because they are eukaryotic
131
What do ergosterol inhibitors do? What type of drug is it?
Ergosterol inhibitors target the unique fungal plasma membrane component ergosterol; it is an anti fungal drug
132
What do Echinocandins do? What type of drug is it?
Inhibit 1,3 beta-D glucan synthase and they are used to treat Candida infections; anti fungal drug
133
What do most anti fungal target?
they target chitin biosynthesis, folate biosynthesis, or disrupt microtubule aggregation
134
What is antimicrobial drug resistance?
The acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive.
135
What are at least six reasons that microorganisms are naturally resistant to certain antibiotics?
1) Organism lacks structure the antibiotic inhibits
2) Organism is impermeable to antibiotic
3) Organism can inactivate the antibiotic
4) Organism may modify the target of the antibiotic
5) Organism may develop a resistant biochemical pathway
6) Organism may be able to pump out the antibiotic (efflux)
136
What are pathogens?
microbial parasites
137
What does pathogenicity mean?
the ability of a parasite to inflict damage on the host
138
What is virulence?
measure of pathogenicity
139
What are opportunistic pathogens?
they cause disease only in the absence of normal heat resistance
140
What is an infection?
Situation in which a microorganism is established and growing in a host, whether or not the host is harmed
141
What is a disease?
Damage or injury to the host that impairs host function
142
What do animals provide to microorganisms? Where do infections frequently begin?
Animals provide a favorable environment for the growth of many microorganisms. Infections frequently begin at sites in the animal’s mucous membranes.
143
What is the normal microflora of the skin like? What is composition influenced by?
The skin is generally a dry, acid environment that does not support the growth of most microorganisms. Most areas (e.g., sweat glands) are readily colonized by gram-positive bacteria and other normal flora of the skin. Composition is influenced by environmental factors (e.g., weather) and host factors (e.g., age, personal hygiene).
144
What kind of microbial habitat is in the oral cavity?
The oral cavity is a complex, heterogeneous microbial habitat.
145
What does saliva contain?
Saliva contains antimicrobial enzymes but high concentrations of nutrients near surfaces in the mouth promote localized microbial growth.
146
How do bacteria colonize tooth surfaces?
Bacteria colonize tooth surfaces by first attaching to acidic glycoproteins deposited there by saliva.
147
What happens if there is an extensive growth of oral microorganisms?
Extensive growth of oral microorganisms, especially streptococci, results in a thick bacterial layer (dental plaque). As plaque continues to develop, anaerobic bacterial species begin to grow.
148
What happens if plaque accumulates in the oral cavity?
As dental plaque accumulates, the microorganisms produce high concentrations of acid that results in decalcification of the tooth enamel (dental caries).
149
What are common agents in the oral cavity?
The lactic acid bacteria Streptococcus sobrinus and Streptococcus mutans are common agents in the oral cavity.
150
The human gastrointestinal (GI) tract consists of what 3 things? WHat it is responsible for? How many microbial cells does it contain?
It consists of stomach, small intestine, and large intestine. It is responsible for digestion of food, absorption of nutrients, and production of nutrients by the indigenous microbial flora. It contains 10^13 to 10^14 microbial cells.
151
What are microbial populations in different areas of the GI tract influenced by?
Microbial populations in different areas of the GI tract are influenced by diet and the physical conditions in the area.
152
What does the acidity of the stomach and the duodenum do?
The acidity of the stomach and the duodenum of the small intestine (~pH 2) prevents many organisms from colonizing the GI tract.
153
What do intestinal microorganisms do? What is the type and amount produced influenced by? What kind of compounds are produced?
Intestinal microorganisms carry out a variety of essential metabolic reactions that produce various compounds. The type and amount produced is influenced by the composition of the intestinal flora and the diet. Compounds produced include vitamins, gas, organic acids, odor, and enzymes
154
What kind of microflora is in the upper respiratory tract? lower respiratory tract?
A restricted group of organisms colonizes the upper respiratory tract (staphylococci, streptococci, diphtheroid bacilli, and gram-negative cocci). The lower respiratory tract lacks microflora in healthy individuals.
155
What kind of microflora exists in the urogenital tract?
The bladder is typically sterile in both males and females. Altered conditions (such as change in pH) can cause potential pathogens in the urethra to multiply and become pathogenic. E. coli and P. mirabilis frequently cause urinary tract infections in women.
156
What does the vagina contain?
The vagina of the adult female is weakly acidic and contains significant amounts of glycogen.
157
What ferments glycogen in the vagina?
Lactobacillus acidophilus, a resident organism in the vagina, ferments the glycogen, producing lactic acid. Lactic acid maintains a local acidic environment.
158
What is virulence?
Virulence is the relative ability of a pathogen to cause disease.
159
How can virulence be measured?
Virulence can be estimated from experimental studies of the LD50 (lethal dose50) [the amount of an agent that kills 50% of the animals in a test group].
160
What is attenuation?
the decrease or loss of virulence
161
What is toxicity?
Organism causes disease by means of a toxin that inhibits host cell function or kills host cells.
162
What is invasiveness?
Ability of a pathogen to grow in host tissue at densities that inhibit host function (can cause damage without producing a toxin).
163
Where does pathogen invasion start and how does it travel?
It starts at the site of adherence and may spread throughout the host via the circulatory or lymphatic systems.
164
What two things to enzymes produced by pathogens do?
Enhance virulence by breaking down or altering host tissue to provide access to nutrients (hyaluronidase). Protect the pathogen by interfering with normal host defense mechanisms (coagulase).
165
What are exotoxins? What are the three categories?
Proteins released from the pathogen cell as it grows. The three categories are cytolytic toxins, AB toxins , and Superantigen toxins.
166
How do cytolytic toxins work?
Work by degrading cytoplasmic membrane integrity, causing cell lysis and death.
167
What are hemolysins?
Toxins that lyse red blood cells are called hemolysins.
168
What does Staphylococcal alpha-toxin kill?
Staphylococcal alpha-toxin kills nucleated cells and lyses erythrocytes.
169
How do AB toxins work? What are 3 examples?
Work by binding to host cell receptor (B subunit) and transferring damaging agent (A subunit) across the cell membrane. Examples are diphtheria toxin, tetanus toxin, and botulinum toxin.
170
What does Clostridium tetani and Clostridium botulinum produce?
Clostridium tetani and Clostridium botulinum produce potent AB exotoxins that affect nervous tissue.
171
What are enterotoxins? What do they generally cause? What is an example?
Exotoxins whose activity affects the small intestine. Generally cause massive secretion of fluid into the intestinal lumen, resulting in vomiting and diarrhea. An example is cholera toxin.
172
Where are streptococcus pyogenes commonly found? What do they cause? When do infections occur?
Commonly found in low numbers in the upper respiratory tract of healthy individuals. Causative agent of “strep throat.” Can also cause infections of the inner ear, mammary glands, and skin. Infections occur if host defenses are weakened or a new, highly virulent strain is introduced.
