Bacteria

Question 1

What are bacterial cell walls made of?

Answer 1

Peptidoglycan

Question 2

What are the 3 common shapes of bacteria?

Answer 2

Bacillus, coccus, spiral

Question 3

What are bacterial chromosomes like?

Answer 3

Single, circular chromosome

Question 4

What is a nucleoid?

Answer 4

Region of condensed DNA that is anchored to the membrane, but not membrane enclosed

Question 5

What 3 structures are only found in some bacteria?

Answer 5

Flagella, pili, capsules

Question 6

What’s the difference between gram-positive and gram-negative bacteria?

Answer 6

Gram positive have a thick PG layer on the outside of the cell membrane, gram-negative have a thin PG layer sandwiched between two membranes

Question 7

Are the outer and inner membranes in gram-negative bacteria composed of the same things?

Answer 7

No, the outer membrane has lipopolysaccharides in the outer leaflet

Question 8

What is the structure of LPS?

Answer 8

Hydrophilic polysaccharide heads, hydrophobic fatty acid tails

Question 9

What does LPS do?

Answer 9

Acts as a chemical barrier against proteins, antibiotics, toxins

Question 10

Why are gram positive bacteria easier to kill?

Answer 10

They only have the physical protection from the PG, they don’t have the chemical protection of the LPS

Question 11

How do gram-negative bacteria get nutrients across the LPS?

Answer 11

Selective porins in the outer membrane

Question 12

How is peptidoglycan structured?

Answer 12

Repeating sugar units of NAG and NAM, with a tetrapeptide chain attached to the NAM sugar. The peptide chain is cross-linked to form a super strong 3D network

Question 13

How is the genetic information in a bacterial cell organized?

Answer 13

Most species have a single circular chromosome, a few have multiple chromosomes, a few more have linear chromosomes

Question 14

Why is the prokaryotic genome streamlined?

Answer 14

Very little DNA is non-coding compared to eukaryotes

Question 15

How is the prokaryotic genome streamlined?

Answer 15

1. No telomeres because the chromosome is circular
2. No centromeres because replication happens by binary fission instead of mitosis
3. Intergenic regions and regulatory elements are small

Question 16

How is the bacterial chromosome condensed?

Answer 16

Looping and supercoiling

Question 17

Do histones aid with DNA condensation in prokaryotes?

Answer 17

No. There are looping proteins but they aren’t histones

Question 18

Why are transcription and translation able to be coupled in prokaryotes?

Answer 18

No membrane is separating transcription and translation, so ribosomes can attach to a binding as soon as its transcribed

Question 19

Why is coupled transcription and translation advantageous?

Answer 19

Allows really fast gene expression

Question 20

What are the 8 reasons why bacteria are good model organisms?

Answer 20

1. Haploid
2. Easy to grow
3. Fast generation time
4. Asexual reproduction
5. Easy to count
6. Easy to isolate
7. Easy to store
8. Easy to genetically manipulate

Question 21

Why does being haploid make bacteria and phages good model organisms?

Answer 21

You only need one copy of a mutation to see an effect since they’re expressed immediately

Question 22

Why can being haploid be disadvantageous for genetic studies?

Answer 22

Difficult to maintain lethal mutations, and mapping can be difficult

Question 23

Why does being easy to grow make bacteria good model organisms?

Answer 23

Can grow really well different mediums that are easy to make, in both solid and liquid medium

Question 24

When would you grow bacteria on a solid plate vs in liquid medium?

Answer 24

If wanting single colony isolates, use solid medium. For lots of colonies, use liquid medium

Question 25

What is generation time?

Answer 25

The time for an organism to reach maturity and reproduce

Question 26

Why does having a short generation time make bacteria good model organisms?

Answer 26

Makes it really easy to get lots of cells in a short period of time

Question 27

Why does having asexual reproduction make bacteria good model organisms?

Answer 27

They divide by binary fission and produce 2 genetically identical daughter cells (clones)

Question 28

Why are bacteria so easy to count?

Answer 28

Every colony that grows originated from a single cell, and easy to plate a serial dilution and do some math to get the original concentration

Question 29

What are we assuming when we do plate counts?

Answer 29

Every colony is genetically identical and the cells are all viable and able to divide

Question 30

Why are the units of a plate count Cfu/ml instead of cells/ml?

Answer 30

Plate counts only count viable cells (aka cfu)

Question 31

Why are bacteria easy to isolate?

Answer 31

Can looks at thousands of colonies at a time to look for a mutant. Much more organisms in a smaller space

Question 32

What is colony purification?

Answer 32

Isolating individuals from a mixture of colonies on a plate, streaking it, taking a single colony, streaking it, and repeating until all colonies are genetically identical

Question 33

Why are bacteria easy to store?

Answer 33

They can be frozen with a cryoprotectant and liquid N2 and stay viable for 20 years. Some also form endospores that can be freeze-dried and stored indefinitely

Question 34

Why are bacteria easy to genetically manipulate?

Answer 34

Can undergo 3 types of genetic exchange (conjugation, transformation, transduction)

Question 35

What is transformation?

Answer 35

The uptake of new DNA from the cell’s surroundings

Question 36

What is conjugation?

Answer 36

The transfer of DNA directly from cell to cell

Question 37

What is transduction?

Answer 37

The introduction of new DNA sequences through a viral vector