Infectious Disease - Bacterial Basics Flashcards
How do bacteria typically replicate?
Binary fission
What is present in eukaryotic membranes but not prokaryotic membranes?
Sterols
(M. pneumoniae is an exception)
Describe the bacterial genome.
Single, circular, nucleoid
True/False.
Besides a nucleus, bacteria have virtually no membrane-bound organelles present.
False.
Bacteria have no membrane-bound organelles.
Describe the following according to shape type:
Cocci
Bacilli
Coccobaccilli
Spirochetes
Filamentous
Diplococci
______cocci typically appear in grape-like clusters.
______cocci typically appear in chains.
Staphylococci typically appear in grape-like clusters.
Streptococci typically appear in pairs or chains.
The purposes of the bacterial cell wall are mainly to prevent _________ damage and also to act as a _________ _________.
The purposes of the bacterial cell wall are mainly to prevent osmotic damage and also to act as a virulence factor.
Describe the general structural difference between Gram-positive and Gram-negative cells.
E.g. Which has a thicker cell wall? How many membranes or walls does each have? What structures are present?
Gram-positive bacteria
_______ (thin/thick) peptidoglycan layer
_______ (present/absent) techoic acids
_______ (present/absent) outer membrane
_______ (present/absent) LPS
_______ (present/absent) porins
Gram-positive bacteria
Thick peptidoglycan layer
Present techoic acids
Absent outer membrane
Absent LPS
Absent porins
Gram-negative bacteria
_______ (thin/thick) peptidoglycan layer
_______ (present/absent) techoic acids
_______ (present/absent) outer membrane
_______ (present/absent) LPS
_______ (present/absent) porins
Gram-negative bacteria
Thin peptidoglycan layer
Absent techoic acids
Present outer membrane
Present LPS
Present porins
Which is generally more susceptible to penicillins, Gram-negative or Gram-positive bacteria?
Gram-positive
Which is generally more susceptible to lysozymes, Gram-negative or Gram-positive bacteria?
Gram-positive
The four steps of Gram staining:
- _____________ is added.
- _____________ is added.
- Alcohol is added.
- Safranin is added.
The four steps of Gram staining:
- Crystal violet is added.
- Iodine is added.
- Alcohol is added.
- Safranin is added.
The four steps of Gram staining:
- Crystal violet is added.
- Iodine is added.
- _____________ is added.
- _____________ is added.
The four steps of Gram staining:
- Crystal violet is added.
- Iodine is added.
- Alcohol is added.
- Safranin is added.
In Gram staining, __________ is added to fix the crystal violet in place in Gram-positive cells.
In Gram staining, iodine is added to fix the crystal violet in place in Gram-positive cell walls.
In Gram staining, __________ is added to wash any non-fixed crystal violet from the cell.
In Gram staining, alcohol is added to wash any non-fixed crystal violet from the cell.
C. All the cells will be red
Iodine step ‘fixes’ purple crystal violet stain within Gram-positive cells.
Without iodine, the alcohol will clear the crystal violet out the Gram-positives and it will be replaced with the safranin red dye.
Gram-positive organisms stain _________ because of ________________ dye.
Gram-negative organisms stain _________ because of ________________ dye.
Gram-positive organisms stain purple because of crystal violet dye.
Gram-negative organisms stain pink because of safranin dye.
The organisms in this slide are Gram-_________.
What other designation would you give them?
The organisms in this slide are Gram-positive.
Streptococci.
The organisms in this slide are Gram-_________.
What other designation would you give them?
The organisms in this slide are Gram-positive.
Staphylococci.
The organisms in this slide are Gram-_________.
What other designation would you give them?
The organisms in this slide are Gram-negative.
Cocci.
The organisms in this slide are Gram-_________.
What other designation would you give them?
The organisms in this slide are Gram-negative.
Rods.
B.
B.
What is the major component of the outer membrane of Gram-negative bacteria?
Lipopolysaccharide
True/False.
O antigen is a major surface antigen present in every Gram-negative bacterial cell wall.
False.
O antigen is a major surface antigen present in many Gram-negative bacterial outer membranes.
Which bacteria are covered in endotoxin?
What is another name for this endotoxin?
Gram-negative;
LPS
The __ side chain of Gram-negative bacteria is immunogenic.
The ______ found in LPS is toxic.
The O side chain of Gram-negative bacteria is immunogenic.
The lipid A found in LPS is toxic.
Which toll-like receptor recognizes LPS?
TLR-4
C.
Bacterial capsules are especially important in preventing ___________ from occurring.
Bacterial capsules are especially important in preventing phagocytization from occurring.
Bacterial capsules are made of what?
Repeating polysaccharide units, protein, or both
True/False.
Bacterial capsules are important in biofilm formation.
True.
The two types of bacterial pilli are:
___________ — multiple per cell; enable adhesion
___________ — single per cell; enables conjugation
The two types of bacterial pilli are:
Common — multiple per cell; enable adhesion
Sex — single per cell; enables conjugation
Fimbriae and pilli both enable what bacterial process?
Adhesion
What protein makes up flagella?
Flagellin
Which toll-like receptor recognizes flagella?
TLR-5
For what two purposes are flagella useful in bacterial life?
Motility;
chemotaxis
True/False.
Many bacteria can quickly alter their flagellar arrangements to create different types of movement and/or different directions of movement and/or become stationary.
True.
What are the four phases of the bacterial lifecycle?
A. Lag
B. Log (exponential)
C. Stationary (plateau)
D. Death
What term describes the length of time it takes for a bacterial generation to double?
(measured during ____ phase)
Doubling time
(measured during log phase)
True/False.
Despite the many differences in the various families of bacteria, the doubling time remains relatively constant among bacterial species.
False.
The doubling time is highly variable among bacterial species.
(E.g.
- E. coli* = ~20 min.;
- M. tuberculosis* = >10 hours)
True/False.
37°C is an optimal temperature for most bacterial growth.
True.
Why is the normal bacterial colonization of our guts and skin actually protective against infection?
Invading bacteria have to compete for resources/space
During which phase of bacterial growth are bacteria most sensitive to antibiotics?
Log phase
(high metabolic need and high replicative function)
True/False.
In a latent infection, the M. tuberculosis doubling time is about 10 hours.
False.
In a latent infection, the M. tuberculosis doubling time is nearly 100 hours.
Why are treatment courses for M. tuberculosis so long?
M. tuberculosis has an extremely slow doubling time
(bacteria are most sensitive during replication)
_________ _________ need oxygen to survive.
_________ _________ are inhibited or killed by oxygen.
Obligate aerobes need oxygen to survive.
Obligate anaerobes are inhibited or killed by oxygen.
Facultative aerobes/anaerobes use ___________ when oxygen is available and ___________ when it is not.
Facultative aerobes/anaerobes use respiration when oxygen is available and fermentation when it is not.
When do microaerophiles grow best?
Low O2 saturation
(can also grow in absence of O2)
Why are some bacterial species killed by oxygen?
Inability to deal with ROSs
How is MacConkey agar selective and differential in promoting bacterial growth?
Selective: inhibits ____________ bacteria (crystal violet and bile salts present)
Differential: different appearance between those that can or cannot ____________ (pH indicator present)
Selective: inhibits Gram-positive bacteria (crystal violet and bile salts present)
Differential: different appearance between those that can or cannot ferment lactose (pH indicator)
Lactose-fermenting organisms appear ______ on MacConkey agar.
Non-lactose-fermenting organisms appear ______ on MacConkey agar.
Lactose-fermenting organisms appear pink on MacConkey agar (acid produced).
Non-lactose-fermenting organisms appear gray on MacConkey agar (no acid produced).
(Image shows plating of a Gram-negative, lactose-fermenting bacteria.)
D.
What testing strip type is shown in the examples here?
For what are they useful?
Analytical profile index;
identifying infectious agents
True/False.
Nutrient depletion triggers bacterial spore formation (by spore-forming bacteria).
True.
Very, very few Gram-________ bacteria can form spores.
Very, very few Gram-negative bacteria can form spores.
What are some potential triggers that might cause reactivation of bacterial spores to a vegetative state?
Presence of water + nutrients;
outer coat disruption (pH change, heat, mechanical stress, etc.)
G. None of the above!
(Autoclave only)
How can bacterial endospores be inactivated?
Autoclave only
Can biofilms be removed from a surface via gentle rinsing?
No
How can non-spore-forming bacteria survive large changes in temperature and other environmental conditions?
Biofilm formation
Name a few common locations in the body and medical devices where biofilms can form.
Urinary catheters;
IUDs;
contact lenses;
plumbing systems;
tooth surface;
CF patient airways
(and many more)
As part of their role in allowing bacterial colonies to survive harsh environments, biofilm formation also increases _____________-resistance.
As part of their role in allowing bacterial colonies to survive harsh environments, biofilm formation also increases antibiotic-resistance.
Bacterial genomes are ______, ______coiled, and double-stranded, with few exceptions.
They are also ususally attached to the cell _________ and central structures.
Bacterial genomes are single, supercoiled, and double-stranded.
They are also ususally attached to the cell membrane and central structures.
The lack of nuclear membrane means what for the central dogma within bacteria?
It is rapid
(transcription and translation occurring simultaneously)
True/False.
Plasmids are self-replicating and often encode essential genes.
False.
Plasmids are self-replicating and rarely encode essential genes.
What do plasmids often confer?
Selective advantage
(via antibiotic properties or virulence factors)
Describe type III secretion systems.
What portion of bacterial genomes often carry type III secretion systems and carry all the components of the bacterium’s necessary virulence factors?
Pathogenicity islands
How do pathogenicity islands differ from normal chromosomal DNA (more G/C content or more A/T content)?
More G/C content
True/False.
Many toxins and virulence factors are easily transferred via plasmids, prophages, transposons, and pathogenicity islands.
True.
Many toxins and virulence factors are easily transferred via plasmids, prophages, transposons, and pathogenicity islands.
Name the type of bacterial genetic transfer represented by each of the following examples in this diagram:
Uropathogenic activity
Enterohemorrhagic activity
Enterotoxigenic activity
Enteropathogenic activity
Transposons
Transduction
Conjugation
Conjugation
Transmission of genetic material between bacteria is usually exchange of __________ or chromosomal __________.
Transmission of genetic material between bacteria is usually exchange of plasmids or chromosomal fragments.
What are the main mechanisms of bacterial genetic recombination?
Conjugation
Transposition
Transduction
Transformation
What are the two main forms of transduction?
Generalized (accidental transfer of fragmented bacterial DNA into phages);
specialized (phage accidentally inserts a particular cleaved DNA into its own material)
The two main forms of transduction are generalized and specialized. How do they work?
Generalized:
Specialized:
Generalized: a phage accidentally takes up fragmented bacterial DNA into its capsule instead of its own genetic material.
Specialized: a phage accidentally inserts a particular cleaved DNA fragment into its own genetic material.
True/False.
Phage therapies may help in combatting resistant bacterial infections.
True.
Bacterial genomics.
Replication –> ________ gene transfer
Recombination –> ________ gene transfer
Bacterial genomics.
Replication –> vertical gene transfer
Recombination –> horizontal gene transfer
__________ — uptake of naked floating DNA floating (can be incorporated into chromosomes or plasmids);
__________ cells are cells able to take up naked DNA.
Transformation — uptake of naked floating DNA floating (can be incorporated into chromosomes or plasmids);
competent cells are cells able to take up naked DNA.
Transposons are mobile genetic elements that often code for antibiotic resistance and are capable of self-replication
Transposons are mobile genetic elements that often code for antibiotic resistance but are incapable of self-replication
Transposons can be either ________ (copy and paste) or non-________ (cut and paste).
Transposons can be either replicative (copy and paste) or non-replicative (cut and paste).
Genes controlling what two enzymes mediate transposon activity?
Transposase and resolvase
____________ can ‘jump’ between plasmids and chromosomes.
Transposons can ‘jump’ between plasmids and chromosomes.
What can be expected to be transferred between F+ and F- cells via normal conjugation?
The F-plasmid (F-factor) only
What can be expected to be transferred between F+ and F- cells via HFR (high-frequency recombination)?
The F-plasmid (F-factor)
+
some chromosomal material
To test antibiotic resistance, place a ______ covered in ____________ on the agar to observe if any growth occurs on the ______.
To test antibiotic resistance, place a disc covered in the antibiotic on the agar to observe if any growth occurs on/around the disc.
What agars are used to identify lactose fermentation in bacteria?
MacConkey or eosin methylene blue (EMB) agars
In an A-B bacterial toxin, the ___ portion binds the cell, allowing for the ___ portion to enter and have an active effect.
In an A-B bacterial toxin, the B portion binds the cell, allowing for the A portion to enter and have an active effect.
The O antigen is present on _________.
The K antigen is present on _________.
The H antigen is present on _________.
The O antigen is present on LPS.
The K antigen is present on capsules.
The H antigen is present on flagella.
The ____ antigen is present on LPS.
The ____ antigen is present on capsules.
The ____ antigen is present on flagella.
The O antigen is present on LPS.
The K antigen is present on capsules.
The H antigen is present on flagella.
All Gram-negative bacteria have endotoxin in the form of __________.
All Gram-negative bacteria have endotoxin in the form of Lipid A (extends from LPS).
What is oxidase?
A respiratory enzyme involved in electron transport
How do oxidase-positive bacteria present on oxidase testing?
How do oxidase-negative bacteria present on oxidase testing?
What is chocolate agar?
Boiled blood agar
What is Thayer-Martin agar?
Chocolate agar (boiled blood agar) + certain antibiotics
What are the functions of teichoic acid and lipoteichoic acid in bacterial membranes?
Adhesion to host cells, antigenic
(also, weak endotoxin activity)
In Gram-negative bacteria, which structure has endotoxin activity?
Which structure has anticomplement activity?
Lipid A;
O-antigen
