Infectious Disease - Bacterial Basics Flashcards by Jason Worley

How do bacteria typically replicate?

Binary fission

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What is present in eukaryotic membranes but not prokaryotic membranes?

Sterols

(M. pneumoniae is an exception)

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Describe the bacterial genome.

Single, circular, nucleoid

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True/False.

Besides a nucleus, bacteria have virtually no membrane-bound organelles present.

False.

Bacteria have no membrane-bound organelles.

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Describe the following according to shape type:

Cocci

Bacilli

Coccobaccilli

Spirochetes

Filamentous

Diplococci

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______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.

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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.

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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?

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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

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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

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Which is generally more susceptible to penicillins, Gram-negative or Gram-positive bacteria?

Gram-positive

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Which is generally more susceptible to lysozymes, Gram-negative or Gram-positive bacteria?

Gram-positive

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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.

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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.

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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.

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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.

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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.

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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.

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The organisms in this slide are Gram-_________.

What other designation would you give them?

The organisms in this slide are Gram-positive.

Streptococci.

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The organisms in this slide are Gram-_________.

What other designation would you give them?

The organisms in this slide are Gram-positive.

Staphylococci.

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The organisms in this slide are Gram-_________.

What other designation would you give them?

The organisms in this slide are Gram-negative.

Cocci.

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The organisms in this slide are Gram-_________.

What other designation would you give them?

The organisms in this slide are Gram-negative.

Rods.

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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

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.)*

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?

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_**, **_super_**coiled, 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: ## Footnote **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