7: Bacteria Overview

Question 1

Bacteria are prokaryotes. Name some characteristics of prokaryotes

Answer 1

1. Unicellular
2. Lack typical organelles like nucleus and mitochondria
3. DNA not encapsulated
4. Reproduce thru binary fission

Question 2

Plasmids

Answer 2

Extra piece of DNA in bacteria that can confer Abx resistance, virulence factors, and other traits such as how to form a pilus for reproduction

Question 3

Color for gram positive vs gram negative bacteria on a gram stain

Answer 3

Gram positive: purple

Gram negative: pink

Question 4

Four steps after heat fixing material to slide for gram staining

Answer 4

1. Primary dye: crystal violet
2. Dye-trapping agent: iodine
3. Decolorizer: alcohol
4. Counterstrain: safranin

Question 5

Major component of gram positive vs gram negative cell walls + a substance found in both

Answer 5

1. Gram positive: teichoic acid and lipoteichoic acid
2. Gram negative: lipopolysaccharide
3. Both: peptidoglycan

Question 6

Two strains of bacteria where gram staining varies as the culture ages

Answer 6

Clostridium, bacillus

Question 7

Gram staining of acid fast bacilli

Answer 7

Contain mycolic acids so gram stain can’t penetrate the waxy cell wall - stain like they’re negative but structurally more gram positive

Question 8

How long does it take to culture bacteria vs fungus

Answer 8

Bacteria: 1-3 days
Fungus: weeks

Question 9

For organisms that dont culture well, what is the best way to detect them in a lab setting?

Answer 9

Serology with Ab positivity

Question 10

Catalase test

Answer 10

If an organism is catalase positive, it will reduce H2O2, producing bubbles when exposed to it