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Exam 1 Flashcards
Terms & Definitions
238
Microbiology
Graduate
03/28/2012

Additional Microbiology Flashcards

 


 

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Term
bright field microscopy
Definition
(most common) source of illumination is visible light, used to visualize bacteria due to contrast difference in bacteria and medium
Term
darkfield microscopy
Definition

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reflected light is used to visualize bacteria too thin to be seen by bright field (e.g. Treponema pallidum) (diagnoses syphillis well)

Term
positive stain
Definition
[image]stains cells, not extracellular medium
Term
negative stain
Definition

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stains extracellular medium, not cells (e.g. india ink stain for visualizing capsules)

Term
Gram stain
Definition

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Procedure = (1) crystal violet - primary stain (purple); (2) iodine - mordant (fixative); (3) alcohol - decolorizer; (4) Saffarnin - counterstain (red)

Term
Why does differential staining occur?
Definition

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Gram-positive cell wall (extensive peptidoglycan layer) retains crystal violet-iodine complex; Gram-negative wall does not

Term
cocci
Definition

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round (shape)

Term
staph-
Definition

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clusters (arrangement)

Term
strep-
Definition

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chain (arrangement)

Term
diplo-
Definition
pairs
Term
bacillus
Definition

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rod (shape)

 

Bacillus are Gram(+)positive

Two Bacillus species are considered medically significant: B. anthracis, which causes anthrax, and B. cereus, which causes a foodborne illness similar to that of Staphylococcus.A third species, B. thuringiensis, is an important insect pathogen, and is sometimes used to control insect pests. The type speciesis B. subtilis, an important model organism. It is also a notable food spoiler, causing ropiness in bread and related food.  

Term
helicoidal
Definition

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curved rod (shape) e.g. Vibrio

Term
helicoidal
Definition

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spirochetal (shape) e.g. Treponema

Term
pleomorphic bacillus
Definition
varies in size and shape e.g. Haemophilus influenzae
Term
H antigen
Definition

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a bacterial flagellar antigen; important in serological identification of bacteria

Term
K antigen
Definition

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a bacterial capsular antigen, external to the cell wall; important for serological identification

Term
biofilms
Definition

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an aggregate of microorganisms in which cells adhere to each other in a self-producing matrix; a protected structure of bacterial cells/microcolonies enmeshed in mucoid (hydrated) exopolysaccharide adhering to a wet surface (inert or living) ... biofilms may form on living or non-living surfaces, and may be prevalent in industrial/hospital settings

Term
fluid mosaic model of the cell membrane
Definition
polypeptides are embedded in the phospholipid bilayer with hydrophilic regions extended out into the cytoplasm, the extracellular volume or both
Term
unit membrane
Definition
phospholipid bilayer with hydrophilic groups at top and bottom and hydrophobic groups in middle
Term
Gram positive
Definition

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bacteria with cell walls consisting of thick layers of peptidoglycan will retain the violet inkstain of the Gram stain procedure

Term
Gram negative
Definition

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bacteria with thinner cell walls with less peptidoglycan will lose the violet inkstain during the decolorization stage of Gram staining procedure

Term
Do both Gram-positive and Gram-negative bacteria possess peptidoglycan?
Definition
Yes
Term
peptidoglycan
Definition

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fabric shell encasing the cell; network of polymers, containing N-acetylmuramic acid and N-acetylglucosamine; N-acetylmuramic acid subunits on different strands are cross-linked via their peptide stems (aka amino acid sidechains), which provides mechanical strength and prevents the cell from bursting via osmotic pressure

Term
LPS
Definition

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lipopolysaccharide (aka endotoxin)

Term
O antigen
Definition

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antigen occurring in the lipopolysaccharide layer of the wall of Gram-negative bacteria

Term
periplasm
Definition

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the peptidoglycan layer … major function is osmotic protection; also function in nutrient uptake, sensory (chemotaxis) mechanism, degradative enzymes

Term
outer membrane
Definition
lipid bilayer … major function is exclusion of some dyes; differentially permeable … Gram-positive bacteria lack an outer membrane
Term
Lipid A
Definition

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composed of disaccharides, phosphate groups, and fatty acids … the toxicity of LPS lipopolysaccharide is primarily associated with Lipid A

Term
core polysaccharide
Definition

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part of LPS lipopolysaccharide; may contain sugars, aminosugar, sugar acids, sugar alcohols; often contains the uniqe sugar ketodeoxyoctulonate (KDO)

Term
KDO
Definition

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ketodeoxyoctulonate; unique sugar found in core polysaccharide of LPS

Term
terminal polysaccharide
Definition

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consists of a unit (sugars, aminosugars, sugar acids, sugar alcohols) repeated N-number of times … highly specific region, e.g. Salmonella

Term
lipooligiosaccharide (LOS)
Definition

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certain bacteria lack O-antigenic (LPS) chain, only contain Lipid A and extended core - e.g. Neisseria meningitidis, N. gonorrhoeae, Haemophilus influenzae, Haemophilus ducreyi

 

LOS is a potent endotoxin that can cause petichae, purpura, septic shock 

Term
exogenous pyrogen
Definition
fever-producing entity (e.g. LPS)
Term
LBP
Definition
LPS Binding Protein
Term
SIRS
Definition

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systemic inflammatory response syndrome … similar to acute inflammation (acute phase response), but on a systemic scale with macrophages, PMNs, endothelial cells serving as effector cells

Term
DS
Definition
distributive shock (hypovolemic shock)
Term
DIC
Definition

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disseminated intravascular coagulation; pathological activation of blood clotting

Term
MOF
Definition
multiorgan failure
Term
sepsis
Definition

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the presence of both (a) proven infection - e.g. pneumonia, UTI, bacteremia, as well as (b) SIRS

Term
severe sepsis
Definition

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the presence of both (a) sepsis [= infection + SIRS] as well as (b) organ failure

Term
septic shock
Definition

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the bresence of both (a) severe sepsis, as well as (b) refractory hypotension

Term
hypovolemic shock
Definition

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caused by loss of fluid from the vascular system; blood pressure drops … not vascular obstructive, not cardiogenic

Term
leukopenia (or leukocytosis)
Definition
abnormally low (or high) levels of peripheral white blood cells in the blood
Term
drotecogin alfa
Definition
activated human recombinant protein C; inhibits clotting, inhibits inflammation, activates fibrinolysis … used as treatment to control SIRS/DS
Term
Protein C
Definition

also known as autoprothrombin IIA and blood coagulation factor XIV ... protein C inhibits clotting (anticoagulant), activates fibrinolysis, inhibits inflammation ... does this by inactivating Factor Va and Factor VIIIa

 [image]

pt's with deficiency or resistance to protein C will be at a significantly increased risk of forming dangerous blood clots (thrombosis)

Term
lipoteichoic acid
Definition

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additional polymer of glycerol or ribitol phosphate, found in Gram-positive cell wall stain … functions in adherence, antiphagocytic

Term
Do the cell walls of Gram-positive bacteria contain LPS/endotoxin, or an outer membrane?
Definition
NO
Term
teichoic acids
Definition

[image] 

additional polymers of glycerol or ribitol phosphate, found in Gram-positive cell wall stain … function to produce endotoxin-like shock, interacts with C-reactive protein, activates alternative complement pathway

Term
TLR
Definition
LPS-signal-transducer receptor protein, located on macrophages, sends the LPS signal through cytoplasm to the nucleus
Term
PAMPs
Definition

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pathogen-associated molecular patterns; include peptidoglycan, teichoic acids, CpG nucleotides, and of course LPS

Term
What are the two genera of endospore-formers?
Definition
Bacillus and Clostridium
Term
virion
Definition

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the complete viral particle

Term
capsomeres
Definition

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protein subunits of the capsid; repetetive polypeptide subunits arranged in symmetric patterns = capsid

Term
capsid
Definition

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the protein shell (or coat) that encloses the core of the NA nucleic acid genome of a virus + any associated proteins

Term
nucleocapsid
Definition

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protein associated with the NA nucleic acid genome; the capsid together with the NA genome plus any associated proteins

Term
envelope
Definition

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the viral membrane; the "skullcap" or "scalp"; viral envelope is composed of virus-specific proteins plus host-derived lipids and carbohydrates (from nuclear, ER, Golgi, or cytoplasmic membranes) that the virus "wears" on its outer membrane; useful for identification

Term
peplomer
Definition

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spikes … viral glycoproteins that form spike-like projections on the surface of the envelope and play a role in attachment

Term
tegument (aka Matrix protein)
Definition

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amorphous layer b/w nucleocapsid and envelope that mediates the interaction b/w capsid and envelope

Term
viroid
Definition
naked RNA virus (mainly plant viruses)
Term
prion
Definition

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infectious protein (misfolded) which causes disease in the CNS … NOT a virus

Term
icosahedral
Definition

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type of capsid symmetry found in animal viruses; capsomeres are arranged in triangles that form a symmetric figure

Term
helical
Definition

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type of capsid symmetry found in animal viruses; capsomeres are arranged in a hollow core that appears helix-shaped

Term
positive sense (+) ssRNA
Definition

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positive sense RNA resembles mRNA and thus can be immediately translated by the host cell ... the viral nucleic acid serves as mRNA, but they must encode for an RNA-dependent RNA polymerase to make the antisense RNA to produce the viral genome

Term
retroviruses
Definition

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have a reverse transcriptase (RNA dependent-DNA polymerase) which transcribes the (+)ssRNA to DNA, then the mRNA is transcribed from the viral specific DNA … this is the target for many anti-HIV drugs, e.g. AZT

Term
negative sense (-) ssRNA and ds-RNA
Definition

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RNA viruses can be classified according to the sense or polarity of their RNA. Positive sense viral RNA is similar to mRNA (can be immediately translated); whiel negative-sense RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA polymerase before translation

These virions must contain functional proteins (an RNA-dependent-RNA polymerase) to make the mRNA as well as possess the gene that codes for the protein

Term
primary replication
Definition
is at or near the portal of entry (POE) for a virus
Term
viral tropism
Definition
where virus has specificity for a particular host tissue
Term
productive infection
Definition

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involves lethal or non-lethal damage/alteration to cells and their functions, as a result of infection

Term
persistent infection
Definition

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involves periods of incubation or persistence, where there is an absence of disease symptoms during infection

Term
tumor (neoplasm)
Definition
a mass of new tissue which persists and grows independently of its surrounding structures
Term
malignant transformation (neoplasm)
Definition
the conversion of a cell from restricted growth to unrestricted growth, which is characteristic of tumors
Term
dimorphism
Definition

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ability of fungus to grow as a mycelial (mold) form at room temperature and a yeast form at 37*C

Term
mycelial fungi
Definition

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growth occurs by elongation of hyphae to form a mycelium … sexual and asexual spores produced

Term
hyphae
Definition

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a long, branching filamentous structure of a fungus, or also the unrelated Actinobacteria (hypha of penicillum, above) ... cells are branching cylindrical tubules +/- septa or crosswalls; collectively called mycelium

Term
mycelium
Definition

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mass of intertwined hyphae

Term
yeasts
Definition

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eukaryotic microorganisms classified under the kingdom fugi ... yeasts are unicellular; asexual reproduction by budding

Term
blastospores
Definition

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aka yeast

Term
macroconidia
Definition

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large (macro) spores (conidia), which are not enclosed in any sort of special structure, naked spores … macroconidia are infectious form for fungi that infect skin (Dermatophytes)

Term
microconidia
Definition

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small (micro) spores (conidia), which are not enclosed in any sort of special structure, naked spores … microconidia are small enough to get to alveoli when inhaled and are the infectious form for certin fungi

Term
symbiosis
Definition
a close association of two different organisms
Term
mutualism
Definition
a beneficial association for two different organisms
Term
commensalism
Definition
beneficial association of one organism with another (unaffected) organism
Term
parasitism
Definition
beneficial association of one organism, to the detriment of another organism
Term
rhizopods (amoebas)
Definition

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protozoa; microscopic; single cells … motile by means of cytoplasmic extensions (pseudopodia)

Term
flagellates
Definition

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protozoa; microscopic; single cells … motile by means of flagella

Term
ciliates
Definition

[image] 

protozoa; microscopic; single cells … motile by means of cilia

Term
sporozoans
Definition

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protozoa; microscopic; single cells … complex life cycles with asexual and sexual stages

Term
helminths
Definition

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the worms. Adults mostly macroscopic, eggs microscopic. Mostly monoecious w/ male and female sex organs in the same individual

Term
monoecious
Definition
male and female sex organs in the same individual
Term
platyhelminthes
Definition

[image] 

flatworms

Term
trematodes
Definition
the flukes
Term
cestodes
Definition

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tapeworms

Term
nemathelminthes
Definition

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round worms, nematodes

Term
arthropods
Definition
chitinous exoskeletons, e.g. lice, mites, ticks, etc.
Term
definitive host
Definition
host which harbors adult or sexual stage of the parasite
Term
intermediate host
Definition
host(s) in which asexual stage(s) occur
Term
autotrophic metabolism
Definition
source of all carbon building blocks is CO2; autotrophic bacteria "fix CO2" … cellular energy is obtained from the oxidation/reduction of inorganic ions (chemoautotroph) or harvesting light energy (photoautotroph)
Term
heterotrophic metabolism
Definition
sources of energy and carbon are organic carbon sources … most pathogenic bacteria are heterotrophic
Term
fastidious microbes
Definition

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have complex growth requirements (specific nutrient, atmospheric, or temperature demands); this makes them difficult to cultivate in the laboratory

Term
non-fastidious microbes
Definition

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have less complex growth requirements, and are easier to cultivate in the laboratory

Term
halophiles
Definition

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"salt lovers", e.g. Vibrio chlorae, V. parahaemolyticus

Term
mesophiles
Definition
growth occurs between 20-50*C … most pathogens are mesophiles & grow best at 35-36*C
Term
thermophiles (obligate or facultative)
Definition
"heat lovers"; grow at temperatures greater than 55*C
Term
psychrophiles or cryophiles (obligate or facultative)
Definition
grow at temperatures less than 20*C (think "cryo"genics, etc.)
Term
aerobes
Definition

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can grow in the presence of O2 because they produce enzymes which detoxify superoxide radicals and hydrogen peroxide

Term
facultative anaerobes
Definition

[image] 

can grow in the presence of O2 because they produce enzymes which detoxify superoxide radicals and hydrogen peroxide

 

Some examples of facultative anaerobic bacteria are Staphylococcus (Gram positive), Escherichia coli and Shewanella oneidensis (Gram negative), andListeria (Gram positive). Certain eukaryote phyla are also facultative anaerobes, including fungi such as yeasts and many aquatic invertebrates such asNereid (worm) polychaetes, for example. There are also circulating white blood cells that are classified as facultative anaerobes. These include neutrophils,monocytes and tissue macrophages.  

Term
superoxide dismutase (SOD)
Definition

[image] 

enzyme of aerobes that detoxifies superoxide anion (O2*-)

Term
catalase
Definition

[image] 

enzyme of aerobes that detoxifies H2O2

Term
obligate aerobes
Definition

[image] 

require the presence of atmospheric O2 for growth, e.g. Mycobacterium tuberculosis

Term
microaerophilic organisms
Definition

[image] 

require the presence of some O2 but NOT at atmospheric levels (reduced O2), e.g. Campylobacter

Term
facultative anaerobes
Definition

[image] 

can grow in the presence or absence of O2 … many pathogens are facultative anaerobes, e.g. enteric bacteria

Term
aerotolerant anaerobes
Definition

[image] 

can survive in the presence of O2, e.g. Lactobacillus spp.

Term
obligate anaerobes
Definition

[image] 

are killed by the presence of O2, they are lacking in the enzymes superoxide dismutase and catalase, e.g. Clostridium, Bacteroides, and others

Term
respiration
Definition
an enzymatic process occurring in a membrane vesicle or sack; the function of which is to provide energy via Proton Motive Force for ATP synthesis (production) during the conversion (recycling) of NADH2 to NAD
Term
aerobic respiration (aka oxidative phosphorylation)
Definition

[image] 

O2 is the terminal electron acceptor, which is reduced to water by the electron transport system … common among pathogenic microorganisms and humans

Term
anaerobic respiration
Definition

[image] 

inorganic compounds (nitrate, sulfate, etc.) serve as terminal electron acceptors … this is significant especially for pregnant females, high levels of nitrites can cause methemoglobinemia (MetHb) especially in the fetus

Term
fermentation
Definition
simpler and less efficient than respiration … fermentation consists of catabolic pathways where organic compounds serve as electron donors and electron acceptors; substrates are partially oxidized generating end products which are 1,2,3,4 carbon compounds, as electron acceptor, and are excreted/released from the cell
Term
dental carries (cavities)
Definition
a fermentation process … bacteria like streptococcus mutans produce lactic acid, which demineralizes the tooth
Term
acification of skin and vagina
Definition
a fermentation process … bacteria like Lactobacillus sp. (produces lactic acid) and Propionibacterium acnes (produces propionic acid) all lower pH of tissues
Term
hydrogen lyase
Definition
enzyme responsible for recycling ferredoxin from the reduced to the oxidized form, in the fermentation process typical for many species of Clostridium
Term
urease
Definition
microbial enzyme that hydrolyzes urea, producing ammonia (NH4+) and CO2
Term
calculi
Definition

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kidney stones … the more alkaline pH in the urinary tract, the more the Ca2+ and NH4+ ions in the urine can form salts which may precipitate out, accumulating in stones

Term
lag phase
Definition

[image] 

phase in the growth cycle, in which there is no change in cell number

Term
exponential/log phase
Definition

[image] 

follows lag phase in the growth cycle … growth occurs at an exponential/logarithmic rate during this phase

Term
generation time
Definition

[image] 

the time required for a parent to divide into two daughter cells … also known as the doubling time

Term
stationary phase
Definition

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phase in the growth cycle which follows log phase and where no net increase in cell numbers occurs

Term
death phase
Definition

[image] 

defined as the phase which follows the stationary phase of the growth cycle, and where cell death begins to occur at a logarithmic rate

Term
fulminant infections
Definition
rapidly progressing … from the latin fulminare meaning "to strike with lightning" ... fulminant infections may be produced by bacteria with a short mean generation time ... may also refer to onset of disease (e.g. fulminant liver failure, fulminant meningitis)
Term
chronic infections
Definition
bacteria with a long generation time generally produce chronic infections, a low Ag dose
Term
genome
Definition
the set of all chromosome(s) of an organism
Term
genotype
Definition
complete listing of all genes present in an organism
Term
phenotype
Definition
complete listing of all physical characteristics that an organism expresses under a defined set of conditions
Term
replicon
Definition

[image] 

a DNA or RNA molecule that controls its own replication and is capable of self-duplication

Term
extra chromosomal elements
Definition
replicons that are present in a cell, excluding the host cell DNA, and including plasmids, baccteriophages (bacterial viruses)
Term
plasmids
Definition

[image] 

plasmids are DNA molecules that are separate from, and capable of replicating independently of, the chromosomal DNA; they are considered replicons, capable of autonomous replication, although they use the bacteria's replication machinery ... plasmids are double stranded covalently closed circular DNA molecules which reside in the bacterial cytoplasm. So they are extra-chromosomal elements.

Term
conjugative plasmids
Definition

[image] 

encode for a mechanism of plasmid transfer (sex pilus)

Term
R factors (plasmids)
Definition

[image] 

encode for drug resistance

Term
Virulence plasmids
Definition
ecnode for virulence factors
Term
bacteriophages
Definition

[image] 

viruses (either DNA or RNA) which infect bacteria. Some bacteriophages can exist in a latent state in the bacterial cells. The viral DNA (prophage) either integrates into the host cell's chromosome or functions as a plasmid in the bacterial cytoplasm.

Term
lysogenized bacteria
Definition
bacteria with latent phages (have prophages); in contrast with phages that go through only a lytic cycle (lyse bacteria)
Term
phenotypic variation
Definition
the situation in which ALL cells in a population respond to environmental stimuli in the SAME fashion, and produce a new/altered phenotype via the expression of a gene(s) … no genotypic change is needed for this to occur … e.g. capsule production by the yeast Cryptococcus neoformans
Term
quorum sensing
Definition

ability of bacteria to detect the size of their own population; a system of stimulus and response correlated to population density; can be used to coordinate gene expression

 

Some of the best-known examples of quorum sensing come from studies of bacteria. Bacteria use quorum sensing to coordinate certain behaviors based on the local density of the bacterial population. Quorum sensing can occur within a single bacterial species as well as between diverse species, and can regulate a host of different processes, in essence, serving as a simple communication network. A variety of different molecules can be used as signals. Common classes of signaling molecules are oligopeptides in Gram-positive bacteria, N-Acyl Homoserine Lactones (AHL) in Gram-negative bacteria, and a family of autoinducers known as autoinducer-2 (AI-2) in both Gram-negative and Gram-positive bacteria. 

Term
genotypic variation
Definition
when the genome (genotype) of one or more cells is/are altered … the acquisition of new genetic information occurs by two different processes -- mutation or horizontal gene transfer
Term
mutation
Definition
alteration in nucleotide sequence of a gene; process of acquiring new genetic information that involves INTERNAL change of the genome
Term
horizontal gene transfer
Definition

[image] 

process of acquiring new genetic information that involves acquisition of a gene from EXTERNAL sources

Term
transformation
Definition

[image] 

mechanism of horizontal gene transfer … occurs when there is replacement of a portion of the recipient's genome are replaced by homologous chromosomal genes from another (donor) bacteria; recipient must be "competent," so it can incorporates free donor DNA into its genome, e.g. recombination

Term
conjugation
Definition

[image] 

mechanism of horizontal gene transfer … when the source of external genetic information is a conjugative (transmissable) plasmid carrying new or altered genes (from donor cell)

Term
transduction
Definition
[image]mechanism of horizontal gene transfer, where DNA is transferred from one bacterium to another by a virus or viral vector; does not require cell-to-cell contact (unlike conjugation) … transduction involves lysogeny (prophages), i.e. acquisition of bacteriophages (as a prophage, latent virus)
Term
bacteriophages
Definition

[image] 

bacterial virus; any number of viruses that infect bacteria ... they do this by injecting genetic material (ssRNA, dsRNA, ssDNA, dsDNA) that was stored in their capsid into the bacteria ... phages are one of the most common and diverse entities in the biosphere

Term
lytic phage
Definition

[image] 

infects the bacterial host cell, replicates, then kills (lyses) the bacterium releasing the new progeny to injfect other cells … involved in transduction, form of horizontal gene transfer

Term
temperate phage
Definition

[image] 

infects the host bacterial cell, after which the phage has two options - either undergo the normal lytic cycle (infect, replicate, then lyse) or can become latent thus "lysogenizing" the bacterium (either by reamaining as plasmid in cytoplasm or by integrating/inserting into host cell DNA)

Term
latent virus
Definition

[image] 

can remain latent inside bacterial host cell either by remaining as a plasmid in the cytoplasm or by integrating/inserting into the host cell DNA

Term
lysogenic conversion
Definition

[image] 

when the recipient bacterial host cell is infected by a temperate virus … a bacterium exhibits a new phenotype due to the acquisition of a prophage (latent bacteriophage) which encodes for the new phenotype

Term
plasmid analysis
Definition
used epidemiologically to determine common source of infecting organisms … plasmid DNA is isolated, purified, DNA fragments are separated by size; detection methodology involves staining = (+) positive match means strains of the same organism possess same number and size of plasmids; (-) negative match means strains with different number or sizes of plasmids, not epidemiologically related
Term
polymerase chain reaction (PCR)
Definition

[image] 

PCR is the in vitro amplification of target DNA or RNA from an organism; the purpose is to amplify nucleic acid sequences which cannot be detected directly … i.e. standard for diagnosis of specific agents detection of Herpes simplex virus JC virus, enteroviruses, rabiesvirus in CNS

Term
normal flora (NF)
Definition

[image] 

Microorganisms that are expected to be present, and that under normal circumstances do not cause disease, but instead participate in maintaining health, are deemed members of the normal flora. 

 

Normal flora bacteria can act as opportunistic pathogens at times of lowered immunity.  

Term
selective anatomical distribution
Definition
characteristic of natural flora (NF); microorganisms have specialized ecological niches (anatomical locations) in and on the body … due in part to attachment sites, nutritional needs, competition, inhibitory substances
Term
coliforms
Definition

[image] 

indicators of fecal contamination and food; Gram-negative rods, facultative anaerobes

Term
natural flora, regions
Definition
see table
Term
endogenous parasite
Definition
when normal flora (NF) becomes opportunist (opportunistic infections, usually their virulence is low) … host suffers, microbes benefit
Term
exogenous pathogen
Definition
classical infectious disease; when an external microbe not part of normal flora causes damage to its (healthy) host
Term
endotoxin (LPS)
Definition

[image] 

produced by Gram-negative organisms, is pyrogenic (fever-causing), is heat stable (survives autoclaving), does not form toxoids, broad spectrum of activity (affects a wide variety of animal species)

Term
exotoxins
Definition
produced by Gram-positive and Gram-negative bacteria; polypeptides or proteins that are either secreted or cell-associated, can be chromosomal or plasmid-encoded or carried on temperate bacteriophages (lysogenic conversion), usually heat labile, can form toxoids (highly immunogenic) generally do not induce fever (not pyrogenic)
Term
pathogen
Definition
a microbial life form that is a harmful symbiont; the etiologic agent of an infectious disease
Term
Frank pathogen
Definition

[image] 

essentially always cause infection and/or disease in a specific host

Term
opportunistic pathogen
Definition
infect and/or cause disease only in compromised hosts (immunosuppressed, malnourished, have cancer, etc.) … also can be normal flora (NF) that become pathogenic due to some changes in the host
Term
non-pathogens
Definition

[image] 

microbial life form that essentially never cause disease, even if the host is severely compromised (e.g. lactobacillus)

Term
pathogenesis
Definition
the evolution of a disease within a host (the "course" of disease)
Term
pathogenicity and virulence
Definition
essentially interchangeable terms that describe the degree to which a pathogen causes disease
Term
virulence
Definition
the degree of pathogenecity; degree to which a pathogen causes disease
Term
virulence factors
Definition

determinants of virulence; any of a pathogens genetic, biochemical or structural features that enable it to produce disease in a host

virulence factors allow pathogens to colonize a host, evade immune responses, and obtain nutrition

 

Some virulence factors are intrinsic (capsule, endotoxin) while others are obtained from external (plasmids). LPS is the prototypical endotoxin; exotoxins include the tetanus toxin and the botulinum toxin 

Term
colonization
Definition
presence of microorganisms in a site of the body that does not necessarily lead to tissue damage and signs/symptoms of disease
Term
symptoms
Definition
effects of bacterial infection apparent to the infected person (the subjective side of describing and determining pain) … e.g. chills, pain, ache, soreness, irritation, nausea, malaise
Term
signs
Definition
the objective side of describing and determining pain/disease, such as temperature or blood pressure … examples = fever, antibodies in serum, blood pressure, heart beat, respiratory range, complete blood work
Term
carriage
Definition

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similar to colonization; refer to someone who is actually infected or has been previously infected with a pathogen, carries that pathogen with them as part of their normal flora (transmission potential), but does not exhibit disease manifestations referable to the pathogen (i.e. inapparent carriage; or in salmonella carriage)

Term
mutualism
Definition
both benefit
Term
commensalism
Definition
host not harmed, microbe benefits
Term
parasitism
Definition
host suffers, microbes benefit
Term
ID50
Definition
measure of virulence; amount of organism that will infect 50% of susceptible animals
Term
LD50
Definition
measure of virulence; amount of organism that will kill 50% of susceptible animals
Term
inapparent (subclinical) or asymptomatic infection
Definition
presence of pathogen; but no detectable clinical symptoms of infection (except seroconversion w/ antibodies does occur)
Term
dormant (latent) infection
Definition

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pathogen is present; but not active or manifest

Term
primary infection
Definition

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clinically apparent invasion and multiplication of microbes in body tissues, causing local tissue injury

Term
secondary infection
Definition
microbial invasion subsequent to primary infection
Term
mixed infection
Definition
two or more microbes infecting the same tissue
Term
acute infection
Definition

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rapid onset (hours or days) and brief duration (days or weeks)

Term
subacute infection
Definition
infection is not chronic but runs a rapid and severe, but less than acute, course; thus, it is intermediate between acute and chronic
Term
chronic infection
Definition
infection w/ prolonged duration (weeks, months, or years)
Term
localized infection
Definition
infection confined to a small area or to an organ
Term
generalized infection
Definition
infection disseminated to many body regions
Term
pyogenic infection
Definition
pus-forming infection
Term
fulminant infection
Definition
infection that occurs suddenly and intensely and are rapidly progressive
Term
superinfection
Definition
literally, an infection "on top of", as a result of, or in addition to the primary infection … often, these result from antimicrobial treatments … e.g. pt prescribed antibiotics for a UTI, and a yeast infection develops as a result
Term
mixed infection
Definition
infection caused by more than one organism simultaneously
Term
coinfection
Definition
this is when two infections appear together, they are often interdependent but are always simultaneous … closely related to the term superinfection (all superinfections are coinfections) … e.g. approximately 80% of TB patients have HIV
Term
disease
Definition
a specific set of manifestations of damage referable to specific pathogen-host interactions … from the Old French meaning "away from the normal" … disease spectrum ranges from asymptomatic to fatal progression
Term
epidemiological triad
Definition

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disease comes from a unique combination of events involving a (harmful) agent, a (susceptible) host, all in the same (proper) environment … disease can be blocked at any three of these "sides" of the "triangle"

Term
host factors
Definition
anything from innate or genetic susceptibility to disease, or psycho-social factors that affect the "host" angle of the epidemiological triad … interventions here would include hygiene, quarantine, immunization, etc.
Term
environmental barriers
Definition
anything from the availability of vectors, to the weather/seasonality, to the existence of reservoir hosts that makes up the "environment" angle of the epidemiological triad … interventions here would include handling/treatment of water/waste, appropriate food handling, controlling temperature, adequate ventilation, etc.
Term
agent factors
Definition
anything about the infectious agent such as persistence or survivability, toxins or virulence factors, that affects the "agent" angle of the epidemiological triad … interventions here include sterilization and disinfection measures
Term
reservoir of infection
Definition
a continual source of infection … can be living (humans w/ disease) or non-living (soil or water or food)
Term
contact transmission
Definition
involves either direct contact (sexual, kissing) or indirect contact (by vehicle such as water or food or soil or blood)
Term
vehicle transmission, by a medium
Definition
involves transmission via water or food or air or soil or blood or fomite
Term
fomite
Definition
any inanimate object or substance capable of carrying infectious organisms
Term
vehicle transmission, by vector (live carrier)
Definition
such as in the case with transmission via arthropods … either a biological vector (part of the life cycle of the pathogen, in saliva or in feces) or by a mechanical vector (passive transport of a pathogen on a vector's feet or other body part)
Term

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zoonoses

Definition
those infections spread from animals (their natural reservoir) to humans as a receptive/susceptible and propagating host … zoonoses tend to be more serious (morbidity) and often fatal (mortality) in humans than in their natural animal reservoirs
Term
non-communicable infectious diseases
Definition
are not transmitted from one person to another; normal flora can be a source, so can preformed microbial toxins or environmental pathogens; but there is no person-to-person transmission
Term
communicable (person-to-person) infectious diseases
Definition
diseases that are transmitted person-to-person … can be spread horizontally (airborne, fecal-oral, bloodborne, etc.) or can be spread vertically (mother to fetus)
Term

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herd immunity

Definition
refers to the indirect effect of protection from infection of otherwise susceptible members of a populations and the population as a whole (herd) as a result of the presence of immune individuals … varies with different infectious agents … for most infectious diseases, only a small fraction of the population (herd) can be left unvaccinated for herd immunity to be effective
Term
firewall
Definition
in herd immunity, immune individuals provide a firewall against the spread of an infectious disease from person-to-person
Term
incubation period (incubation time)
Definition

the time between exposure to a pathogen and the appearance of the first symptoms of disease

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Term
chemoprophylaxis
Definition

administration of antimicrobials prior to onset of symptoms

 

antibiotics, for example, can be administered to patients with disorders of immune system dysfunction, to prevent opportunistic infection 

Term
immunoprophylaxis
Definition
passive or even active immunization prior to the onset of symptoms
Term
incidence
Definition
number of new occurrences of disease, injury, or death in the study population during the time period being examined
Term
seasonality
Definition
if the incidence rate (new occurrences) is consistently higher during a specific time of year, e.g. influenza demonstrates winter seasonality
Term
prevalence
Definition
the total number of existing cases with respect to the entire population (100%) … prevalence = incidence (new cases) + old cases
Term
mortality rate
Definition
measures the total number of deaths in a population due to a certain disease
Term
morbitity rate
Definition
measures the total number of persons afflicted with infectious diseases
Term
endemic/endemicity
Definition
the rate at which infection or disease is present - a certain constant rate (the endemic rate)
Term
epidemic
Definition

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a significant (and usually sudden) increase above the endemic and sporadic rate of a disease … could be hours, days, months

Term
common source epidemic
Definition
an epidemic where all individuals are exposed to one specific source
Term
point source epidemic
Definition
an epidemic where all individuals are exposed to a specific source at a particular time
Term
propagative or progressive epidemics
Definition
indicates a transmissable or communicable disease
Term
pandemic
Definition

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a global epidemic (above the normal global endemic rate)

Term
sporadic
Definition
occasional cases of a disease at irregular intervals in random locales
Term
epizootic
Definition
epidemic zoonoses … above the endemic/sporadic rate
Term
enzootic
Definition
endemic zoonoses … within the range of endemic/sporadic observed rate
Term
risk factor
Definition
an attribute, characteristic, agent, etc. that is, or is suspected to be, related to the occurrence of a particular disease … help to identify populations at risk … thus can occasionally rule-out or rule-in certain diseases … more often used to rank-order possibilities in synthesizing a differential diagnosis from most likely to least likely ... e.g. age, gender, occupation, geography, etc.
Term
siRNA
Definition
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA molecules, 20-25 nucleotides in length, that play a variety of roles in biology. The most notable role of siRNA is its involvement in the RNA interference (RNAi) pathway, where it interferes with the expression of a specific gene.
Term
type species
Definition
A type species is the species to which the name of a genus is permanently linked; it is the species that contains the biological type specimen(s) of the taxon. This is an important concept whenever a taxon containing multiple species must be divided into more than one genus; the type species automatically assigns the name of the original taxon to one of the resulting new taxa, thus reducing the potential for confusion.
Term
How do plasmids differ from viruses?
Definition
Plasmids are considered replicons, capable of replicating autonomously within a suitable host. Plasmids can be found in all three majordomains: Archaea, Bacteria, and Eukarya.Similar to viruses, plasmids are not considered by some to be a form of life. Unlike viruses, plasmids are naked DNA and do not encode genes necessary to encase the genetic material for transfer to a new host, though some classes of plasmids encode the sex pilus necessary for their own transfer. Plasmid host-to-host transfer requires direct, mechanical transfer byconjugation or changes in host gene expression allowing the intentional uptake of the genetic element by transformation.Microbial transformation with plasmid DNA is neither parasitic nor symbiotic in nature, because each implies the presence of an independent species living in a commensal or detrimental state with the host organism. Rather, plasmids provide a mechanism for horizontal gene transfer within a population of microbes and typically provide a selective advantage under a given environmental state. Plasmids may carry genes that provide resistance to naturally occurring antibioticsin a competitive environmental niche, or the proteins produced may act as toxins under similar circumstances. Plasmids can also provide bacteria with the ability to fix elemental nitrogen or to degrade recalcitrant organic compounds that provide an advantage when nutrients are scarce.
Term
latent, reactivating infection
Definition

 

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 e.g. herpes simplex virus 

Term
slow virus infection
Definition

w/ periods of dormancy

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 e.g. measles virus (SSPE); human immunodeficiency virus (HIV)

Term
toxoid
Definition

A toxoid is a bacterial toxin (usually an exotoxin) whose toxicity has been weakened or suppressed either by chemical (formalin) or heat treatment, while other properties, typically immunogenicity, are maintained.

 

Toxoids are used as vaccines because they induce an immune response to the original toxin or increase the response to another antigen. For example, the tetanus toxoidis derived from thetetanospasmin produced by Clostridium tetani. The latter causes tetanus. Botulin is produced by Clostridium botulinum and it causes the deadly disease botulism.  

Term
septum
Definition

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Septum is a small fissure formed during bacterial cell division ... Bacteria reproduce by an asexual process called binary fission. First, the DNA replicates and the cell elongates. In the middle of the elongated cell, a septum forms and this develops in to a cell wall that divides two seperate cells.

Term
transpeptidase or penicillin binding proteins (PBP)
Definition
the enzyme responsible for completing the final cross-linking (transpeptidation) process in the synthesis of peptidoglycan
Term
Why are chemotherapeutic inhibitors of protein and/or peptidoglycan synthesis more effective against fast-growing than against slow-growing organisms?
Definition

Inhibition of peptidoglycan synthesis inside an actively-dividing cell results in osmotic lysis; so if an organism is dividing more frequently, it will be lysed more frequently by the antibiotic

 

many antimicrobials utilize this - e.g. the penicillins, the cephalosporins, the carbapenems

Term
host range
Definition
The host range or host specificity of a parasite is the collection of hosts that an organism can utilize as a partner. In the case of human parasites, the host range influences the epidemiology of the parasitism or disease.
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