Introduction to Bacteria

Question 1

What type of bacteria is shown from this differential staining?

Answer 1

Gram (+)

Question 2

What type of bacteria is shown from this differential staining?

Answer 2

Gram (-)

Question 3

Describe the differences between gram (+/-) bacteria that make them stain different colors.

Answer 3

The structure of their cell walls.

Gram (+) bacteria have a thick, uniform peptidoglycan cell wall.

Gram (-) have a thin peptidoglycan cell wall, plus an outer membrane consisting of lipopolysaccharide (LPS).

Question 4

Describe the 4 key characteristics of prokaryotes (bacteria).

Answer 4

1. Unicellular
2. Lack a membrane-bound nucleus
3. Lack membrane-bound organelles
4. Smaller & less complex than eukaryotes

Question 5

What is the process of binary fission?

Answer 5

2 daughter cells resulting from a single cell replicating its own DNA

Question 6

Describe acid-fast bacteria.

Answer 6

Bacteria with thick, outer lipid-rich layers comprised of mycolic acids, which render “acid-fast” bacteria that are resistant to becoming decolorized (with acid-alcohol) once stained red. Can survive inside cells and are targets for other antibiotics.

Question 7

What is the importance of differential staining of bacteria?

Answer 7

Antimicrobial therapy = the most effective when it is narrow-spectrum targeted. The type of bacteria determines the drug type (i.e., how the cell wall can be degraded)

Question 8

What shape of bacteria is shown?

Answer 8

Coccus

Question 9

What shape of bacteria is shown?

Answer 9

Rod (or Bacillus)

Question 10

What shape of bacteria is shown?

Answer 10

Sprillum/Spirochete

Question 11

What shape of bacteria is shown?

Answer 11

Mycobacteria

Question 12

What shape/arrangement of bacteria is shown?

Answer 12

Corynebacteria (palisades arrangement)

“Coryne” = rod-like shaped
Palisades = fenced arrangement

Question 13

What shape of bacteria is shown?

Answer 13

Coccobaccilli

Question 14

What arrangement of bacteria is shown?

Answer 14

Streptococci (cocci in chains)

Question 15

What arrangement of bacteria is shown?

Answer 15

Staphylococci (large cocci in irregular clusters)

Question 16

What arrangement of bacteria is shown?

Answer 16

Spore-forming rods

Question 17

What arrangement of bacteria is shown?

Answer 17

Streptomycetes (mold-like, filamentous)

-mycete = mushroom, fungus

Question 18

What are the features of the “capsule” that encloses some bacteria?

Answer 18

Amorphous, gelatinous material enclosing around the cell wall; has pili attached to it; comprised of carbohydrates; antigenically diverse; anti-phagocytic!

Question 19

Can you see capsules in a gram stain?

Answer 19

No

Question 20

What is the importance of determining if a bacterium is enclosed in a capsule or not?

Answer 20

Determines type of antimicrobial needed (i.e., for cell-wall penetration/degradation)

Question 21

Describe the gram stain protocol.

Answer 21

1. Heat-fix
2. Stain with crystal violet
3. Stain with iodine treatment
4. Stain with de-colorizer
5. Counter-stain with safranin
6. Will be either purple or pink

Question 22

What is the purpose of pili?

Answer 22

Adherence

Question 23

What is the purpose of flagella?

Answer 23

Motility

Question 24

What is the importance of bacterial spores?

Answer 24

Dormant form of bacteria that are resistant to harsh conditions (extreme temperatures/pH; antibiotic exposure; lack of nutrition)

Question 25

What forms a single colony on an agar plate?

Answer 25

A single bacterium that has undergone clonal expansion

Question 26

If the # of colonies increases, then the # of bacteria ___.

Answer 26

increases

Question 27

What are the two states bacteria can exist in?

Answer 27

Planktonic (free) or sessile (attached)

Question 28

What forms a biofilm, and what state of bacterium is it?

Answer 28

Biofilm: sessile Formed when a bacterial population becomes adherent to each other and/or a surface, and then becomes enclosed within a biopolymer matrix = "goop"

Question 29

What is quorum sensing?

Answer 29

A communication mechanism used by bacteria within a biofilm that allows them to function as one/an "organism"

Question 30

How do biofilms aid in the pathogenesis (development) of bacterial infections? (3)

Answer 30

1. Aid in colonization 2. Aid in avoiding phagocytosis 3. Aid in avoiding antibiotics

Question 31

Which type of bacteria requires O2 for growth (respiratory catabolism)?

Answer 31

(Strict or obligate) aerobes

Question 32

Which type of bacteria is killed by O2 (fermentative pathways)?

Answer 32

(Strict or obligate) anaerobes

Question 33

Which type of bacteria can grow either aerobically or anaerobically?

Answer 33

Facultative Anaerobes

Question 34

Which type of bacteria require reduced O2?

Answer 34

Microaerophiles

Question 35

What type of infection can you rule out anaerobic bacteria from your differential dx?

Answer 35

Surface-skin infection

Question 36

What is the importance of knowing the atmospheric requirements of bacteria?

Answer 36

Influences your dx approach, which influences your tx plan

Question 37

Where do anaerobic bacteria live in the body?

Answer 37

**Epithelial** surfaces of: **G.I. tract lumen**, gums, vagina

Question 38

Describe the bacterial genome.

Answer 38

Haploid; circular chromosome with dsDNA

Question 39

What is the significance of the plasmid molecule in bacteria?

Answer 39

carries genes for antibiotic resistance

Question 40

What are 3 ways bacteria can undergo genetic variation?

Answer 40

1. **Mutation** (change in nucleotide seq) 2. **Recombination** (exchange of DNA b/w two separate bacteria; transduction, conjugation, transformation) 3. **Transposition** (transposons "jumping genes"/integrons move locations within the genome, or integrate into plasmid --> jump to other bacteria)