Term
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Definition
| individual unit of genetics; DNA sequence encoding a polypeptide |
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Term
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Definition
| genetic makeup of organism |
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Term
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Definition
| total genetic makeup of an organism |
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Term
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Definition
observable characteristics
Examples:
Flagella
Cell wall composition
Ability to metabolize carbohydrates |
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Term
DNA Replication in Bacteria |
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Definition
Semiconservative DNA replication
Each synthesized copy contains one new and one old strand. |
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Term
DNA Replication in Bacteria bidirection replication |
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Definition
Bidirectional Replication
Two replication forks move around the DNA forming intermediates |
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Term
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Definition
Single chromosome
Length - 1.4 mm
Genome size:
4.6 million bases
Approx. 4,300 genes |
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Term
Mechanisms of Genetic Change |
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Definition
Mutations
Change in single bases, additions or deletions
May cause single amino acid change
Recombination
Whole chromosomes or regions of chromosome transferred between cells |
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Term
ΠPoint mutation: Change in single base Are due to: |
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Definition
Are due to:
Mistakes by DNA polymerase
Occur rarely; are corrected by “proof-reading”
Alteration of bases after DNA synthesis
Caused by chemicals or radiation |
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Term
Effects of Point Mutations 4 different types |
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Definition
Silent mutation - no effect
AGG CGG Both code for Arg
Missense mutation - changes amino acid
AGG (Arg) GGG (Gly)
Neutral mutation - change to equivalent AA
AAA (Lys) AGA (Arg)
Nonsense mutation - creates a stop codon
CAG (Gln) UAG (stop) |
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Term
Mutations Insertion/Deletion Mutations : Extra bases added (or deleted) during DNA replication |
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Definition
Caused by intercalating agents
Insert themselves between the stacked bases of the helix
Ex: ethidium bromide
Causes distortion of DNA
Causes “frame shift” mutations |
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Term
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Definition
Morphological mutants
Change in cell wall, colony morphology
Lethal mutant
Cell death
Conditional mutant
Mutation expressed in certain conditions (i.e. temp)
Biochemical mutants
Auxotroph - cannot synthesize certain compound
Prototroph - wild-type |
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Term
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Definition
Treat cells with mutagen
Add agent to kill “wild type”
Only mutants will grow
Ex: Penicillin-resistance |
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Term
Selection of Mutants Indirect: Replica Plating |
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Definition
Expose cells to mutagen
Compare growth on complete media vs. growth on “minimal” media (lacking an essential component)
Ex: Lysine |
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Term
The Ames Test - Used to Identify Chemical Mutagens |
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Definition
Rapid screening method
Uses mutant Salmonella strain
his auxotroph - unable to synthesize histidine
Mix Salmonella his- with test chemical
Plate on histidine-deficient media
Only revertant his+ cells with grow
Significance of Ames Test
Mutagenesis => carcinogenesis
If chemical is a mutagen, it may cause cancer in animals
Ames test is used as a rapid screen for carcinogenic compounds |
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Term
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Definition
Recombination:
Process in which one or more nucleic acid molecules are rearranged and combined to produce a new nucleic sequence (typically genetic material from two parents is combined)
Recombination in bacteria:
occurs following horizontal gene transfer
is one-directional
Donor Recipient |
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Term
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Definition
transfer of genes from one mature, independent organism (donor) to another (recipient)
exogenote
DNA that is transferred to recipient
endogenote
genome of recipient
merozygote
recipient cell that is temporarily diploid as result of transfer process |
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Term
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Definition
Vertical Gene Transfer
Genes are transferred from parent to offspring
Horizontal Gene Transfer
Genes are transferred between cells in same generation |
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Term
Mechanisms of Horizontal Gene Transfer in Bacteria |
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Definition
DNA transfer between bacteria occurs via
Conjugation
transfer between bacteria
Transformation
uptake of “naked” DNA
Transduction
transfer via a virus |
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Term
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Definition
Transfer of DNA between bacteria
Requires direct contact via sex pilus
Can transfer
Plasmids
Episomes
Partial or whole chromosomes |
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Term
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Definition
Circular DNA molecules
Contain less than 30 genes
Exist independently of chromosome
Have replication origins |
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Term
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Definition
Episomes:
Plasmid that can integrate into chromosome
Conjugative plasmids:
contain genes for pili and can transfer copies of themselves |
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Term
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Definition
Fertility factors (F factor)
Are conjugative plasmids
Contain genetic information for formation of sex pili
Are episomes - can integrate into chromosome
Resistance factors (R plasmids)
Have genes for antibiotc resistance
Encode enzymes capable of destroying or modifying antibiotics
Are usually conjugative plasmids
May contain transposons
Col plasmids
Encode bacteriocins bacteriocidal are proteins that destroy other bacteria
Virulence plasmids
Encode toxin genes make host more pathogenic
Metabolic plasmids
Encode genes for enzymes
Some allow degradation of unusual carbon sources |
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Term
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Definition
Segments of DNA that move from one chromsomal location to another
Allow movement of genes between chromosome and plasmids
Allows antibiotic resistance genes to move from chromsome plasmid other cells |
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Term
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Definition
Fertility factors (F factor)
Are conjugative plasmids
Contain genetic information for formation of sex pili
Are episomes - can integrate into chromosome |
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Term
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Definition
transfer of DNA by direct cell to cell contact
discovered 1946 by Lederberg and Tatum
Mixed two auxotrophic strains
Incubated the culture for several hours in nutrition media
Plated on minimal medium
Growth! |
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Term
The U-tube experiment (Bernard Davis) |
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Definition
demonstrated that direct cell to cell contact was necessary
after incubation in nutrient medium,
bacteria plated on
minimal medium
->
no prototrophs |
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Term
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Definition
F+ x F- mating
Hfr x F- mating
F ’ Conjugation |
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Term
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Definition
Cell with fertility factor plasmid (F+ cell) transfers plasmid to F- cell
Recipient cell becomes F+ |
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Term
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Definition
Hfr (high frequency of recombination) cell has F factor plasmid integrated into chromosome (exhibits high efficiency of chromosomal gene transfer in comparison with F+ cells)
Transfers part or all of chromosome to F- cell
F- cell remains F-, but may recombine with donated DNA
Note:
DNA transfer begins when the integrated F factor is nicked at its site of transfer origin
Because only part of the F factor is transferred at the start the F- recipient usually does not become F+ |
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Term
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Definition
used to map relative location of bacterial genes
based on observation that chromosome transfer occurs at constant rate
Interrupted mating experiment (“Blender”):
Hfr x F- mating interrupted at various intervals
order and timing of gene transfer determined |
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Term
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Definition
If F factor in Hfr cell leaves chromosome, it may pick up portion of chromosomal DNA
Resulting plasmid is called an F’ plasmid
F ’plasmid is transferred to F- cell
F- cell becomes F ’ cell |
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Term
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Definition
Uptake of “naked” DNA
1st observed by Griffith in 1928
Recipient cells must be “competent” for DNA uptake
Dependent on growth cycle
Requires expression of proteins needed for transformation |
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Term
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Definition
Transfer of genes via virus infection
Bacteriophage:
Virus that infects bacteria
Generalized Transduction:
During lytic life cycle of bacteriophage (please see book), virus assembly may incorporated host genes into progeny virus
Specialized Transduction
Specific bacterial genes transferred
Occurs via bacteriophages with lysogenic life cycle |
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Term
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Definition
Impairment of body function due to presence of an organism (bacteria, virus)
Pathogen: organism that causes disease
Parasitism: symbiotic relationship in which host is harmed |
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Term
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Definition
Primary pathogens - cause disease in any healthy host
Opportunistic pathogens - normally is free-living or normal flora; is a pathogen in certain conditions |
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Term
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Definition
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Term
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Definition
Degree (intensity) of pathogenicity; due to:
Infectivity - ability to colonize host
Invasiveness - ability to spread in host tissues
Pathogenic potential - ability to form toxins or induction of immunopathology |
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Term
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Definition
| Cell structures or molecules involved in disease process |
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Term
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Definition
ID50 - infectious dose for 50% of population (within a specified period)
LD50 - lethal dose for 50% of population (within a specified period) |
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Term
•Pathogenesis - process of disease causation •Includes: |
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Definition
Attachment of microbe
Invasion through host tissues
Evasion of host defenses
Mechanisms of damage to |
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Term
| Contact and Entry into Host |
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Definition
Source of organism: disease reservoirs
Humans, Animals, Environmental
Modes of transmission:
Contact, Vehicles (food or water), Vectors
Portals of entry
Respiratory, Gastrointestinal system, Urogenital system, Skin |
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Term
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Definition
| use adherence structures (fimbriae, capsules, adhesins, etc.) |
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Term
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Definition
Colonization - must compete with normal flora organisms to establish site of reproduction
Note:
Not necessarily tissue invasion or damage at this point! |
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Term
| Invasion and Growth in Host |
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Definition
Invasion may be passive or active
Passive invasion - via cuts, scratches, via insect vector, engulfment by phagocyte, etc.
Active invasion - via production of lytic enzymes, attack on cell surface
Growth: in or on host cells - Host may supply necessary nutrients (ex: heme groups or ATP) |
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Term
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Definition
Survival of the most clever bacteria!
Evasion of complement system:
G-bacteria - lengthen “O” chains on LPS
Resistance to phagocytosis
Capsules - Streptococcus pneumoniae, Neisseria, Haemophilus |
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Term
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Definition
Direct cell damage - via host cell invasion and lysis
Toxin-mediated damage:
Endotoxin - produced by G- bacteria
produced as bacteria divide or die
Exotoxin - produced by G+ bacteria (& some G- bacteria)
produced by living bacteria |
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Term
Exotoxin
•Source
•Chemistry •Effect on host •Heat Stability •Toxicity •Immunology •Fever •Genetics •Representative diseases |
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Definition
Source
G + bacteria (& some G-)
Secreted by living bacteria
Chemistry
Protein
Effect on host
Specific effect on specific cell
Heat Stability
Unstable (inactivated at 60-80o)
Toxicity
Highly toxic in small amounts
Immunology
Can vaccinate
Fever
Usually no fever
Genetics
Gene may reside on plasmid
Representative diseases
Tetanus, Botulism, Diphtheria |
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Term
Endotoxin
•Source
•Chemistry •Effect on host
•Heat Stability
•Toxicity •Immunology •Fever •Genetics •Representative diseases
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Definition
Source
G- bacteria
Released by dying bacteria
Chemistry
Lipid A portion of LPS
Effect on host
Similar for all endotoxins: fever, weakness, inflammation
Heat Stability
Heat-stable
Toxicity
Moderate toxicity (high lethal dose)
Immunology
No vaccines available
Fever
Induces fever via IL-1 release
Genetics
Encoded by chromosomal genes
Representative diseases
Meningocococal meningitis,
Typhoid fever
(ANY G- bacteria) |
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Term
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Definition
Block or activate specific neurons
May be ingested pre-formed
Clostridium botulinum - Botulinum toxin
Or, may be formed in body
Clostridium tetani - Tetanus toxin |
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Term
Mechanism of Botulinum Toxin Action |
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Definition
| Botox blocks neurotransmitter release; Causes “flaccid paralysis” |
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Term
| Membrane-Disrupting Toxins |
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Definition
Phospholipases
Ex: Clostridium perfringins a-toxin |
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Term
| Endotoxin in Bacterial Diseases |
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Definition
Endotoxin has indirect effects on host
LPS enters monocytes and macrophages
Host cells release cytokines fever
Induction of Fever by Endotoxin
The increased body temperature helps the body's immune system to fight infection. |
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Term
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Definition
Purpose: To prevent infectious disease
Type of immunity:
- Active immunization
Vaccine is administered
Induces protective immunity
Passive immunization
artificially acquired
can be produced by injecting preformed antibodies (produced in animal, human or in vitro) |
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Term
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Definition
Whole-organism vaccines
- Inactivated (killed) organisms
- Attenuated (weakened) organisms
Purified macromolecule vaccines
- Capsules, toxoids, surface antigens
Recombinant vector vaccines
- Attenuated recombinant nonpathogenic microorganism
- contains gene that encodes antigen from a pathogen
DNA vaccines not approved yet |
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Term
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Definition
| Kill the microbe, not the host! |
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Term
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Definition
Ratio toxic dose to therapeutic dose
Higher ratio, more effective agent |
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Term
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Definition
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Term
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Definition
affects one or a few types of microbes
Ex: Penicillin G kills G+ bacteria |
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Term
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Definition
affects many types of microbes
Ex: Tetracycline kills both G+, G- bacteria and intracellular bacteria |
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Term
| Categories of diseases
Natural, semi-synthetic, synthetic |
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Definition
“Natural” - Synthesized by microbes
Fungi - Penicillum and Cephalosporium
Bacteria - Bacillus and Streptomyces
Semi-synthetic - isolated from microbes, modified in the laboratory
Synthetic - directly synthesized in the laboratory |
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Term
| Antibacterial Agents may inhibit: |
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Definition
cell wall synthesis
protein synthesis
nucleic acid synthesis
specific enzymes |
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Term
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Definition
Cell Wall Synthesis Inhibitors
The b-lactam antibiotic:
Inhibit transpeptidation step of peptidoglycan synthesis
Bacteriocidal |
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Term
•Penicillin G - “natural” penicillin |
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Definition
Penicillin G - “natural” penicillin
Effective against G+ bacteria (some G-)
Must be injected; Destroyed by stomach acid |
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Term
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Definition
Some bacteria produce penicillinase (also called b-lactamase)
Penicillin converted to penicilloic acid |
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Term
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Definition
Protein Synthesis Inhibition
Bind 30S subunit; inhibit aminoacyl tRNA binding
Broad spectrum: Affects both G+ and G- and intracellular bacteria
Bacteriostatic |
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Term
| Aminoglycosides: Streptomycin |
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Definition
Protein Synthesis Inhibition
Aminoglycosides: Streptomycin
Bind 30S subunit; Cause misreading of mRNA
Bactericidal
Toxic side effects: deafness & allergic response |
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Term
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Definition
Protein Synthesis Inhibition
Macrolide: Erythromycin
Binds 50S subunit
Broad spectrum
Bacteriostatic |
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Term
Quinolones: Nalidixic acid Fluoroquinolones: Ciprofloxacin |
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Definition
Inhibition of Nucleic Acid Synthesis
Quinolones: Nalidixic acid
Fluoroquinolones: Ciprofloxacin
Inhibit DNA gyrase; inhibits DNA replication
Broad-spectrum |
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Term
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Definition
Inhibition of Specific Enzymes
Sulfonamide
Inhibit folic acid synthesis; inhibits purine and pyrimidine synthesis
Sulfanilamide competes with p-aminobenzoic acid
during folic acid synthesis
Decline of folic acid in cell
inhibits DNA/RNA synthesis |
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Term
| Medical Microbiology: Food and Waterborne Diseases
(Chapter 39) |
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Definition
Disease frequency:
2nd most common type of infectious disease
Effect on world health:
10% of children under 5 yrs die due to acute diarrheal illnesses
Source of infection:
Food, Water, Human carriers
Transmission mode:
Oral / Fecal |
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Term
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Definition
Food and waterborne
Causative agent: Clostridium botulinum
Mode of transmission:
Ingestion of toxin in food (home-canned foods)
Signs/symptoms:
Flaccid paralysis
Death due to respiratory or cardiac failure
Virulence factors:
Neurotoxin - blocks nerve transmission
Treatment: Antisera
Prevention:
Improved food preservation methods |
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Term
| Staphylococcal “Food Poisoning” |
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Definition
Food
Causative agent:
Staphylococcus aureus
Source of organism:
Person preparing food
Foods associated with outbreak:
Examples: Ham, cream pies, puddings
Any foods cooked and left at room temperature
Incubation Period:
1-8 hours
Signs and symptoms:
Nausea, vomiting, abdominal cramps, diarrhea
Treatment:
Oral or I.V. rehydration; Recovery in 24-48 hrs
Prevention:
Handwashing by food preparer
Refrigeration of foods!! |
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Term
| Helicobacter Peptic Ulcer Disease |
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Definition
Food and waterborne
Causative agent:
Helicobacter pylori
Signs and symptoms:
Erosion and ulceration of stomach lining
Treatment:
Antibiotics + Pepto-bismol
The ammonia that is produced is toxic to the epithelial cells of the stomach
Along with the other products including protease, catalase and phospholipases!
These products cause damage to epithelial cells |
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Term
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Definition
airborne
Causative agent:
Corynebacterium diphtheriae
Mode of transmission:
Airborne
Respiratory droplets
Signs & Symptoms:
Cold-like; fever, sore throat;
Pseudomembrane in throat
Virulence Factors:
Exotoxin - encoded by lysogenized phage
Toxin inactivates EF-2; Blocks protein synthesis
Treatment:
Antibiotics + Anti-toxin antisera
Prevention:
DPT vaccine (diphtheria, pertussis and tetanus) |
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Term
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Definition
airborne
Predisposing Factors:
Prior viral infection - cold or influenza
Exposure to pollution
Smoking
Poor nutrition, alcoholism, drug use
Other health problems - heart, lung, etc. |
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Term
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Definition
airborne
Causative agent:
Streptococcus pneumoniae
G+ coccus; forms capsule
Signs & Symptoms:
Fever, Chest pain & Cough
Virulence Factors:
Capsule
Pneumolysin (damages the blood vessels in the lungs)
Treatment: Antibiotics
Vaccine: Streptococcal pneumonia vaccine |
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Term
| Anthrax / Woolsorters’ Disease |
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Definition
contact diesease
Causative agent: Bacillus anthracis
Mode of transmission:
Via cuts in skin - anthrax
Inhalation - Woolsorters’ disease
Signs/symptoms:
Cutaneous (skin) anthrax - Skin pustule
Pulmonary anthrax - Woolsorters’ disease – Pneumonia (~100% lethal)
Treatments: Antibiotics (if given early)
Prevention: Vaccine available |
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Term
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Definition
contact disease
Causative agent: Clostridium tetani
Mode of transmission: Puncture wound
Signs/symptoms:
Muscle spasms
“Lock-jaw”
Death due to suffocation
Virulence factors:
Neurotoxin: tetanospasmin
Blocks inhibitory neurons ( overactivity in the muscles)
Treatment:
Passive immunization with human anti-tetanospasmin immunoglobulin
vaccine booster
Prevention:
DPT vaccine |
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Term
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Definition
=reexposure to the immunizing antigen
It is intended to increase your immunity against that antigen back to protective levels after it has been shown to have decreased or after a specified period of time (eg tetanus shot boosters every 10 years). |
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Term
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Definition
Vector Borne
Causative agent: Yersina pestis
Mode of transmission:
Vector: rat flea
Reservoirs: squirrels, rats, prairie dogs
Signs/symptoms:
Swollen and blackened lymph nodes (buboes)
Fever |
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